compiling practical teaching content of automotive body electrical systems

MINISTRY OF EDUCATION AND TRAINING HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION GRADUATION THESIS AUTOMOTIVE ENGINEERING TECHNOLOGY COMPILING PRACTICAL TEACHING CONTENT OF AU

INTRODUCTION

Reasons for choosing the topic

As the economy is developing, people's living standards are improving day by day The demand to be provided with the best is a legitimate need

A modern automotive today can be likened to a mobile building That means, it is not possible to stop only at ensuring the safety, economic efficiency or aesthetics of a vehicle, but also to ensure that it is equipped with comfortable systems and equipment As a result the structure of wiring harness inside getting more and more complex, which make many people find it very difficult when they first access with body electrical system

As students of Ho Chi Minh University of Technology and Education, one of the top tier university in the quality of human resource training in the automotive industry in the southern region, our team realized the importance of this project, it helps students to learn and practice in a practical way without having to use an expensive automotive to practice

Stemming from the above reasons, we would like to automotivery out the project:

" Compiling practical teaching content of Automotive Body Electrical Systems ".

Topic’s objective

- Compiling Practical Teaching Content Of Automotive Body Electrical Systems

- Repair for all training models

- The statistics and classification of all training models

- Build instructional videos on how to use all models

- Build practice sheets for all models

- Software for studying and taking tests after class

Object and study range

- Structure and function of the automotive body electrical systems

- Circuit diagram of automotive body electrical systems

- Operating principle of automotive body electrical systems

- Field: Basic automotive body electrical systems (Lighting system, Wiper-washer system, Power window system, Door lock system, Power mirror system, Power sunrooof system, Power seat system, Information system, Air conditioning system)

Research methods

- Methods of synthesizing, comparing, and analyzing information from books and documents of automobile manufacturer

Literature review

In Vietnam, the interest in developing educational content for automotive electrical systems is surging, mirroring the global shift towards more advanced automotive technologies With the automotive industry booming, Vietnamese universities and technical schools are enhancing their curricula to include comprehensive programs on automotive electrical systems These programs, often developed in partnership with automotive companies and foreign institutions, equip students with essential theoretical and practical skills for the evolving market, covering topics from basic electrical theory to the design of electric and hybrid vehicles

Despite progress, challenges like limited access to modern facilities and a shortage of experienced educators persist However, the growing need for skilled automotive engineers in electrical systems is driving continuous improvements in educational offerings, preparing students for both local and global industry demands

The development of educational content for automotive electrical systems globally is dynamic and closely aligned with industry advancements, particularly in countries with a strong automotive sector like Germany, the U.S., Japan, and South Korea Educational institutions are collaborating closely with automotive manufacturers to ensure curricula encompass both foundational electrical engineering principles and the latest innovations in hybrid and electric vehicles, autonomous systems, and advanced diagnostics This integration provides students with hands-on learning opportunities, internships, and access to cutting-edge technology, preparing them effectively for the workforce

Research and development also play a critical role, with significant investment from both the public and private sectors fueling advances in vehicle electronics and electromobility This research enriches educational content, ensuring it reflects current technological progress

Overall, the international approach to teaching automotive electrical systems is marked by its strong industry linkage, research integration, and innovative pedagogical methods, preparing students for a rapidly evolving automotive landscape

LIGHTING AND SIGNALING SYSTEM

Introduction

Automotive lighting and signaling systems are among the most crucial components of modern automobiles This system encompasses exterior lighting such as low-beam headlights, high-beam headlights, fog lights, position lights, brake lights, license plate lights, and so on Interior lighting includes reading lights, overhead lights, dashboard lights, door lights, trunk lights, and so forth Signaling devices such as horns, warning lights, and turn signals and flashing are also part of this system

Depending on their function, different types of lights and signaling devices on automobiles are employed appropriately for specific operating conditions, ensuring safety and convenience for drivers and passengers In addition to the general lighting system, vehicles are equipped with systems that serve various purposes depending on the market and vehicle type

The front lighting system is a fundamental yet crucial component that enhances visibility for drivers during low-light conditions, limited visibility, or restricted driving environments It also alerts surrounding vehicles, oncoming drivers, and pedestrians to the vehicle's presence and its intended direction of travel The lighting system is typically positioned on both sides of the vehicle's front end

The rear lighting system plays an equally crucial role as the front lighting system, enabling drivers behind to identify the vehicle's size, receive signals when the vehicle is braking or stopping, and consequently minimize the risk of collisions The lighting system is typically positioned on both sides of the vehicle's rear end

Navigating the interior of a car during nighttime or low-light conditions can be challenging due to limited visibility The entry lighting system addresses this issue by automatically activating lights within the vehicle upon closing the doors This illumination serves to highlight the ignition switch, floor area, and other essential elements, enabling drivers to locate controls and perform actions with greater ease and convenience

Leaving interior lights on can drain the vehicle's battery, leading to a dead battery To prevent this, the interior light reminder system automatically turns off interior lights (including dome lights and ignition switch lights) after a specified period This feature activates when the ignition is in the "LOCK" position or when the key is not inserted into the ignition switch

Figure 1.4 Interior light reminder system [4]

The signaling system plays a crucial role in ensuring road safety for drivers This essential component enables drivers to communicate their intentions to surrounding vehicles, signaling actions such as turning, stopping, reversing, or encountering hazards

Assisted lighting system

During dense fog conditions (high humidity), airborne water droplets reflect a significant portion of the light emitted by headlights, creating a glare that hinders visibility for oncoming vehicles and pedestrians

Drivers may not be aware of malfunctioning tail or brake lights, posing a safety hazard to themselves and others The taillight warning system addresses this issue by alerting the driver to burned-out tail or brake lights through an indicator light on the instrument panel This system is controlled by a bulb failure sensor and is typically located in the trunk compartment The bulb failure relay detects burned-out bulbs by comparing voltages under normal operating conditions and when a circuit is open

Figure 1.8 Rear light warning system [4]

Manually activating headlights can be inconvenient, especially when transitioning between different lighting conditions The automatic lighting control system can fix this by automatically switching on headlights when the ambient light level falls below a certain threshold This feature is typically activated by setting the multifunction switch to the "AUTO" position Some vehicles may not have an "AUTO" setting on the headlight switch

Figure 1.9 Automatic lighting control system [4]

4 Headlight and position light reminder/Automatic shutoff system

Leaving headlights and other lights on even when the ignition is in the "LOCK" position and the headlight switch is in the "ON" position can drain the vehicle's battery The headlight and position light reminder/automatic shutoff system solve this issue by alerting the driver that the lights are still on through an audible warning or by automatically turning off the lights

In this system, either the low-beam headlights or both the low-beam headlights and position lights automatically illuminate when the engine starts during daylight hours, increasing visibility for other vehicles This system is mandated by law in some countries for safety reasons

Continuous operation at full daytime brightness can shorten the lifespan of bulbs To address this, the circuit is designed to reduce the headlight intensity when the daytime running light system is active

Vehicle pitch can vary depending on loading conditions (passenger count or cargo weight) This can cause headlights to aim too high, potentially blinding opposite drivers The headlamp aiming system addresses this issue by allowing the driver to adjust the vertical angle of the low-beam headlights using a control switch Some vehicles have an automatic headlamp aiming system that automatically adjusts the low-beam headlights to the optimal vertical angle

7 High-intensity discharge (HID) headlight system

The high-intensity discharge (HID) headlight system offers significant advantages in terms of visibility and vehicle aesthetics compared to traditional halogen headlights HID bulbs utilize an electric arc between xenon gas-filled electrodes to produce a brighter, whiter light with a broader illumination pattern Additionally, HID bulbs boast a considerably longer lifespan, further enhancing their appeal

Figure 1.13 Compare between Halogen and HID headlight system [4]

Lightbulbs and lighting technology

The light bulb's casing is made of glass, and inside it contains a tungsten filament The tungsten filament is connected to two wires to provide power These two wires are tightly attached to a brass or aluminum cap Inside the bulb is a vacuum environment to remove air to prevent oxidation and evaporation of the filament (oxygen in the air reacts with tungsten at high temperatures, causing the bulb to darken and after a very short time, the filament will break)

When operating at its rated voltage, the filament temperature reaches up to 2,300 degrees Celsius and produces white light If a voltage lower than the rated voltage is supplied to the lamp, the filament temperature and the emitted light will decrease Conversely, if a higher voltage is supplied to the lamp, it will quickly evaporate the tungsten filament, causing the bulb to darken and the filament to burn out The filament of a high-power bulb (such as a headlamp) is designed to operate at a higher temperature The luminous intensity is increased by about 40% compared to a conventional incandescent lamp by filling the bulb with a small amount of inert gas (argon) at a relatively low pressure

After a long period of use, filament bulbs will experience darkening of the glass casing and reduced light intensity due to the evaporation of the filament To overcome this problem, halogen bulbs were created

Basically, a halogen lamp is an improved type of incandescent lamp with a longer lifespan and higher efficiency than a conventional lamp Halogen lamps contain a small amount

12 of halogen gas, such as iodine or bromine, inside the bulb These gases create a closed chemical process: Iodine combines with evaporating tungsten (or Tungsten) in a gaseous form to form tungsten iodide This gas mixture does not adhere to the glass casing like a conventional lamp, but instead, sublimation movement carries this mixture back to the high-temperature gas region around the bulb's filament (at temperatures above 1450°C)

At high temperatures, it separates into two substances: tungsten adheres back to the filament and halogen gas molecules are released back into a gaseous form This regeneration process not only prevents the discoloration of the bulb but also keeps the filament working in good condition for a long time

Typically, halogen lamps operate at temperatures above 2500°C because at this temperature the halogen gas can evaporate Therefore, for the casing, manufacturers mainly use quartz glass because this material can withstand high temperatures and very high pressures (from 5-7 bar), making the filament glow brighter and have a longer lifespan than conventional lamps In addition, an advantage of halogen lamps is that they only require a smaller filament than conventional lamps, allowing for more precise focus adjustment than conventional lamps

Xenon lamps, also known as HID (High Intensity Discharge) lamps, are a type of lamp that produces high-intensity electric discharge lighting They are commonly installed in automotive lighting systems as a standard feature nowadays

Xenon lamps are considered superior to halogen lamps due to their lighting performance and significantly longer lifespan, approximately 10 times longer than halogen lamps (around 3,000 hours) Regarding the characteristics of Xenon lamps:

 They emit a large amount of heat, so it is not permissible to touch the lamps directly, and cooling components are required

 They emit a white-blue light that is quite similar to daylight conditions, which can help drivers see more easily

 However, they cannot reach maximum brightness in a short period of time, so Xenon lamps are only suitable for use as near-beam or high-beam headlights and are not used in turn signal systems or hazard lights

Figure 1.16 Compared the ligtht intensitive between Xenon and Halogen bulbs [3]

As you can see, Xenon lamps (bottom image) have better illumination intensity and coverage than halogen lamps (top image)

Unlike incandescent or halogen lamps, which are simply bulbs, a Xenon lamp system consists of the following components:

The Xenon bulb housing is usually made of borosilicate glass, which can withstand high temperatures Inside the bulb is Xenon gas, a colorless, odorless inert gas Also contains electrodes, which are the electrical contact points between the Xenon bulb and the ballast and other support components, including gas tubes, shields, and cooling components

A ballast is a device used to provide the necessary electrical conditions for a discharge lamp to operate Ballasts are typically made of plastic or metal and are compact in size, making them suitable for installation on automobiles They also play an important role in ensuring the normal operation of Xenon lamps If the ballast is damaged, the Xenon lamp will not be able to operate or will operate erratically

 Operating Principle of Xenon Lamps

Xenon lamps operate on a principle similar to that of neon lamps When a high-voltage current (around 20,000V) passes through xenon gas, the xenon atoms are ionized and release energy in the form of light Specifically, when the xenon lamp is turned on, the ballast supplies high voltage to the xenon bulb This voltage creates a spark between the two electrodes in the bulb This spark excites the xenon atoms in the bulb and causes them to ionize When the xenon atoms are ionized, they release energy in the form of light

The control unit (ECU) is an electronic control device used to turn on high-pressure discharge headlamps It is located under the left and right high-pressure headlamps It optimizes the current supply to the bulbs to ensure fast and optimal light intensity when the bulbs are lit and continuous, stable light It is equipped with a safety device to prevent the effects of high voltage The positive terminal of the headlamp control unit is extremely dangerous due to the high voltage, so extreme caution must be exercised when handling it To prevent hazards, warning labels are affixed to the side of the lamps and the headlamp control unit

- High Voltage Hazard: The glass and electrodes of the high-pressure headlamps operate at a dangerously high voltage (≈20,000V) Therefore, do not touch them directly

- Proper Power Source: Only turn on the headlamps after the bulbs have been completely installed Do not use any power source other than the vehicle's electrical system

- Bulb Replacement: Follow the procedures outlined in the repair manual when replacing bulbs

 Safety Protection Functions of the ECU

The headlamp control unit (ECU) detects malfunctions and activates safety functions under the following conditions:

If the input voltage is outside the operating voltage range (9 to 16 V), the safety function will turn off the high-pressure headlamps The high-pressure headlamps will turn back on as soon as the input voltage is within the operating range

- Detection of Incorrect Output, Flickering Lights

If the output voltage is incorrect or if the high-pressure headlamps flicker, the safety function will turn off the high-pressure headlamps If this occurs, it is not possible to determine whether the output voltage is incorrect Therefore, first check for damage to the fuses and grounding, and then replace the high-pressure headlamps If the problem persists, the headlamp control unit (ECU) must be replaced

- Detection of Open Headlamp Circuit

Front lighting system

The headlamps assembly includes high beam lights, low beam lights, and flash (Flash) This is one of the most important systems in a car To ensure safety when driving, the front car lighting system must meet the following requirements:

 Appropriate brightness intensity: The brightness of the lighting system must be sufficient for the driver to clearly observe the road Additionally, the intensity of the light should not be too bright, as it could dazzle drivers in the opposite direction, leading to danger for both

 Appropriate distance of the light beam: The range of the light beam must also be within a suitable range Too close can affect long-distance visibility and too far can affect oncoming vehicle

Lighting mode Lighting distance (m) Power consumption (W)

Table 1.1: Standard of lighting distance and power consumption

1.1 Wiring diagram of headlamps assembly without relay control

Figure 1.24 Wiring diagram of headlamps assembly without relay control

To turn on the high beams, switch the headlight control to "Head" and the brightness control to "High."

At this point, the high beam switch will be connected to the ground, allowing current to flow from the battery through the lamp in "High" mode, then through the brightness control and the control switch, and down to the ground

To turn on the low beams, switch the headlight control to "Head" and the brightness control to "Low"

At this point, the low beam switch will be connected to the ground, allowing current to flow from the battery through the lamp in "Low" mode, then through the brightness control and the control switch, and down to the ground

The flashing mode can be activated at any time, even when the switch is in the "OFF" position In this case, the flash pin of the control switch will connect to the ground, allowing current to flow from the battery to the "High" lamp and back to the ground (not through the lamp control switch but only through the brightness control switch)

1.2 Circuit diagram of the negative standby type headlamps assembly

Figure 1.28 Circuit diagram of the negative standby type front lighting assembly

1.3 Circuit diagram of the positive standby type headlamps assembly

Figure 1.29 Circuit diagram of the positive standby type headlamps assembly

1.4 Circuit diagram of headlamps assembly using HID system

Figure 1.30 Circuit diagram of headlamps assembly using HID system

The Daytime Running Light (DRL) system operates continuously when the vehicle is moving during the day, meaning the lights are always on To prevent the lights from always being active, which could lead to overheating or affect their lifespan due to overload, the DRL circuit is designed to be dimmer than the headlights by adding a resistor or connecting the lights in series to reduce power consumption The power of the DRLs can be reduced by 70 to 80% compared to the headlights

2.1 DRL circuit diagram using resistor

Figure 1.31 DRL circuit diagram using resistor

2.2 DRL circuit diagram connected in series

Figure 1.32 DRL circuit diagram connected in series

Fog lights are used in cases of poor weather conditions with dense fog If high beams are used in such conditions, they can create a strong light zone that dazzles drivers coming from the opposite direction; fog lights are yellow Fog lights can only be turned on when in headlight (Head) or taillight (Tail) mode and must be activated along with the position lights (as the voltage is typically drawn after the relay of the position lights)

Figure 1.33 Front fog light circuit diagram

Rear lighting system

Rear lights, also known as taillights, are a lighting system typically placed on both sides at the rear of the vehicle, helping drivers behind to recognize the size of the vehicle Rear lights may be white if installed with reverse lights, or red when installed with brake lights

There are two types of circuit designs for the rear light system:

1.1.1 Taillight circuit diagram without relay control

Figure 1.34 Taillight circuit diagram without relay control

The lights are connected directly after the light control switch without going through a relay This circuit is commonly used in older car models and is less common today

1.1.2 Taillight circuit diagram with relay control

Figure 1.35 Taillight circuit diagram with relay control

This type includes a protective relay installed before the lights and the control switch

It is widely used in current car models

Brake lights are positioned at the rear of the vehicle and are designed to be highly visible even during the day; they are mandated to be red in color When the driver applies the brakes, the brake switch closes, thereby lighting up the brake lights to signal to the driver behind that the vehicle in front is braking, allowing them to react accordingly

Figure 1.36 Brake lamps circuit diagram

The working principle of brake lights is quite simple The brake switch is specially designed so that when the driver presses the brake pedal, the switch closes, completing the circuit This allows voltage to pass through the brake warning light and the brake lights, causing them to illuminate and signal to drivers behind that the brakes are being applied to reduce speed

The reverse lights are installed in the rear light assembly and are white in color When the driver shifts the gear to the R (Reverse) position, the lights immediately turn on to signal to other vehicles that the car is backing up

In older car models, the reverse light system was integrated with a warning horn However, nowadays, most car manufacturers have discontinued the horn feature

Figure 1.37 Reverse lamps with horn circuit diagram

Rear fog lampts may or may not be included depending on the design of the car manufacturer They are used to signal the position to drivers behind when driving in foggy areas or in weather conditions with limited visibility The voltage for these lights is usually taken after the low beam lights, and there is an indicator on the dashboard showing that the fog lights are active

Figure 1.38 Fog lamps circuit diagram

Nowadays, due to the requirements of the Department of Transportation, vehicles must be equipped with license plate lights to facilitate automated fines and toll payments at toll booths during the night The light is installed so that the beam illuminates the license plate, which may include one or two lights depending on the car manufacturer's design License plate lights can be white or yellow and are usually powered by the same electrical source as the rear position light system

Interior lighting systeam

The dome lamps system in a car is a component that provides light for the cabin, helping the driver and passengers to see everything inside the vehicle clearly, especially at night or in dark conditions, such as when traveling through tunnels Additionally, the overhead lighting system also functions as a reminder when any car door is not properly closed, causing the light to turn on

When the user activates the overhead light switch, power is supplied to the light The light will illuminate and provide lighting for the cabin Furthermore, the light is also equipped with sensors on the car doors If a door is opened or not properly closed, the sensors will send a signal and the light will turn on

Figure 1.40 Dome lamps on car

Common types of overhead lights:

 Single overhead light: This type of overhead light has only one bulb and is typically installed in the center of the vehicle

 Dual overhead lights: This type of overhead light has two bulbs, usually installed on the left and right sides of the vehicle

 Adjustable overhead light: This type of overhead light allows for adjustment of brightness and direction of light to suit user needs

 Integrated overhead light: This type of overhead light is integrated with other features such as sunroofs, rearview mirrors, or sound systems

Functions of the overhead lighting system in cars:

 Provides lighting for the cabin, helping the driver and passengers to clearly see everything inside the vehicle

 Creates a comfortable and pleasant atmosphere for the users

 Enhances safety when driving at night or in low-light conditions

 Enhances the aesthetic appeal of the interior

 Allows passengers to use the light for reading or map reading in low-light conditions

Car door lights, also known as door open warning lights, step illumination lights, or sill lights, are small lights installed at the vehicle's door locations with the primary functions of:

 Signaling to other road users that a car door is open: Whenever any door is opened, these lights illuminate to alert people nearby, especially at night or in low-light conditions, helping to prevent collisions and accidents

 Providing lighting for the step area when entering or exiting the vehicle: The light from these lamps makes it easier to see the steps and move safely, particularly at night or in low-light conditions

 Enhancing the aesthetic appeal of the vehicle's exterior: Car door lights contribute to accentuating the exterior of the vehicle, making it look more luxurious and modern

Figure 1.41 Door lamps on car

 When the driver or anyone opens a car door, the car door light switch automatically turns on

 The car door light will automatically turn off when you close the door

 Some cars also have an additional feature that automatically turns off the car door lights after a certain period

When the user opens the trunk, the trunk light switch automatically turns on thanks to a position sensor or travel switch, making it easier for the user to observe the contents inside the trunk, especially at night

Current types of trunk lights:

 Single trunk light: This type of light has only one bulb, usually installed at the center of the trunk

 Dual trunk lights: This type of light has two bulbs, typically installed on the left and right sides of the trunk

 LED trunk lights: This type uses LED bulbs to provide light LED trunk lights are more energy-efficient, have a longer lifespan, and generate less heat compared to incandescent bulbs

 Sensor trunk lights: This type of light automatically turns on when the user opens the trunk and turns off when the trunk is closed

Additionally, some modern cars are equipped with advanced features for the trunk lighting system such as:

 Automatic trunk lighting system: This system automatically turns on when the trunk is opened and turns off when the trunk is closed

 Adjustable brightness trunk lighting system: This system allows the user to adjust the brightness of the trunk light according to their needs

 Trunk lighting system integrated with warning system: This system can be integrated with a trunk door opening warning system, helping the driver to know when the trunk is being opened

Signaling system

To notice the driver when a light is damaged or experiencing issues, a lamp failure circuit is used Essentially, these circuits compare the voltage across the lights to detect any voltage drops There are two main types: circuits that use electronic components and circuits that use a reed switch

Figure 1.42 Lamp failure circuit using electronic components [1]

The lamp failure circuit operates on a relatively simple principle It is based on comparing the voltage at both ends of a conductor When a light bulb fails, its resistance increases This causes the voltage at both ends of the conductor to also rise This voltage is fed into an operational amplifier (OPAMP) The OPAMP compares this voltage with a fixed voltage If the voltage at the conductor ends is higher than the fixed voltage, the OPAMP will output a high voltage signal This signal is then input into an OR logic gate The OR logic gate compares this voltage signal with the voltage signals from other lamp failure circuits If this voltage signal is equal to or greater than the other signals, the OR logic gate outputs a high voltage signal This high voltage signal is then fed into an indicator light located on the dashboard The indicator light illuminates to signal that there is a malfunctioning light

When one or more lights are damaged, the OR logic gate outputs a signal of 1, causing the transistor that controls the malfunction indicator light on the dashboard to light up, signaling that there is a faulty light

Figure 1.43 Lamp failure circuit using reed switch [1]

This structer is commonly used in older car models It consists of two coils wired in series with the light bulb When the light bulb fails, its resistance increases, leading to a reduction in the current passing through the bulb This causes the magnetic field generated by the two coils of the reed switch to also decrease When the magnetic field decreases, the contact of the reed switch closes This then supplies current to the indicator light on the dashboard The indicator light illuminates to signal that there is a faulty light

Figure 1.44 Lamp failure circuit for tail and brake lamps

2 Turn signal light and Hazard

These two types of indicator lights use the same bulbs but different control switches There are a total of 4 lights, with 2 lights placed on each side at the front and two on the back

In some models, additional lights are also designed on the two side mirrors These lights are yellow and operate in a flashing mode

The turn signal switch is located within the combination switch under the steering wheel The turn signal has the function of signaling to vehicles behind and oncoming traffic The turn signal lights can only operate when the car's engine is running

The hazard light switch is located separately and is marked as shown When the hazard is activated, all turn signal lights operate, signaling danger to vehicles behind and oncoming traffic Hazard lights are designed to operate even when the car's engine is off

Unlike other types of lights, the turn signal and hazard warning lights do not stay on continuously but flash; therefore, they require a flashing unit to operate Additionally, this unit also emits a sound to alert the driver inside the vehicle that the system is active Each car manufacturer designs its own flasher, but fundamentally, there are two types:

2.1 Turn signal system with a separate hazard switch

Figure 1.47 Turn signal system with a separate hazard switch on Toyota Corrola

2.2 Turn signal system with an integrated hazard switch

Figure 1.48 Turn signal system with an integrated hazard switch

2.3 Integrated turn signal and hazard control system

Figure 1.49 Integrated turn signal and hazard control system

- When turning on the left turn signal, the turn signal switch and the EL pin of the flasher unit are connected to ground, at this time the transistor will control the LL switch to open and close continuously and the left turn signal light will blink

- Similarly, when turning right, the ER pin will be connected to ground, at this time the

LR pin operates and the right turn signal light will illuminate Since they are wired in parallel, if one bulb fails, the current through the remaining bulb will decrease, thereby increasing the flashing rate => signaling to the driver that one bulb is faulty

- When the hazard lights are turned on, the EHW switch closes and is grounded, at this point both LL and RL pins operate and all four lights will flash

The horn system is a component that allows the driver to warn or attract the attention of surrounding vehicles by creating sound The horn system has a relatively simple structure including components such as:

 Vehicle horn: there can be various types such as electric horns, air horns, etc

Figure 1.50 Horn system on Toyota Camry [4]

When the driver presses the horn button, the horn switch closes, allowing current to pass through the horn relay, which then makes and breaks the electrical connection to the horn The horn vibrates and produces a warning sound

Additionally, modern car horn systems are equipped with some advanced features such as:

 Automatic horn: Automatically emits a warning sound when the car encounters danger, such as during sudden braking or in the event of a collision

 Multi-tone horn: Allows the driver to choose from several different warning sounds

 Adjustable horn volume: Allows the driver to adjust the volume of the horn to suit the surrounding environment.

Assisted lighting system

The automatic lighting control system has the ability to detect environmental light and then control the appropriate lighting modes This system operates through a light sensor (photoresistor) located near the bottom edge of the windshield and cameras When the environmental light changes, the photoresistor changes resistance, causing a change in voltage that leads to control signals for turning the lights on or off according to the light environment Additionally, the cameras help to detect whether the oncoming vehicles are within the high beam range, thereby switching from high to low beam to prevent dazzling other drivers

For example, when driving in the evening as the environmental light conditions darken, the car lights will automatically turn on Similarly, when driving at dawn as the sun rises, the photoresistors will detect the brightness and automatically switch the lights to daytime running lights (DRL) mode To operate in this mode, the driver needs to turn the control lever to the AUTO position

Figure 1.51 Automatic lighting control system [1]

Figure 1.52 Automatic lighting control system using IC 555 [1]

Figure 1.53 Automatic lighting control system using OP-AMP [1]

When the driver exits the vehicle and forgets to turn off the lights, over time this could drain the battery, preventing the car from starting Therefore, this system has the functionality to turn off the lighting (headlights and taillights) when the driver has exited the vehicle without turning off the lights

When the headlights and taillights are on (with the ignition key in the ON position and the light control switch in the TAIL or HEAD position), if the ignition key is turned to the ACC or LOCK position and the driver's side door is opened, the current does not pass through terminal A of the relay assembly When the door switch is activated (as the driver closes the door), terminal B is connected to the ground When this happens, the IC within the relay assembly will cut off the Transistors Tr1 and Tr2 Current does not pass between terminals C and D, E and F, and both the taillights and headlights automatically turn off After activating the automatic light shut-off system, this state can be canceled and the headlights and taillights can be turned back on by turning the ignition key to the ON position and setting the light control switch to TAIL or HEAD

To control the lighting position of the headlights up or down, the driver can turn the control knob Essentially, this knob controls a variable resistor; turning the knob changes the resistance, thereby altering the current in the controller

The controller can rotate the drive motor's output shaft to the desired lighting position

To accomplish this, it contains an IC, considered a potentiometer A potentiometer is an electronic device that can transform a voltage signal into another voltage signal of a different value Depending on the changing control signal, the ICs will control the motor to rotate and move the shaft to the desired lighting position

The rotational position of the headlight switch is recorded by the headlight ICs and sends a signal to the motor When the switch is turned to the left, the current intensity from the switch increases, causing the motor to rotate left Conversely, when the switch is turned to the right, the current intensity from the switch decreases, causing the motor to rotate right

The actuator, where the motor is installed, continuously determines its actual position thanks to the potentiometer Based on the actual position of the actuator, the headlight ICs will control the motor to ensure that the headlight beam angle is appropriate for the operating conditions

1 List the types of light bulbs currently used in vehicles Describe the structure, advantages, and disadvantages of these types of bulbs

2 Describe some phenomena of the turn signal indicator light when a turn signal bulb has burned out

3 In some current car models with Auto mode (automatically turning on the lights when the car enters a tunnel, when it gets dark, or in low light conditions) Describe the location of the sensor and its operating principle

4 Please draw the basic lighting circuit (standby negative lighting circuit and standby positive lighting circuit) and analyze the operating principle of the circuit in each switch control mode

5 Read the following circuit diagram and explain the operating principle of LOW beam and HIGH beam modes

Figure 1.57 Lighting system circuit diagram

WIPER AND WASHER SYSTEM

Introduction

The windshield wiper and washer system have a function to remove water and dirt from the windshield and rear glass, ensuring clearer and longer visibility for the driver, which enhances safety in traffic In older car models, this system only operates when controlled by the driver Newer models are equipped with an automatic wiper system controlled by sensors and ECU

Figure 2.1 Wiper and washer system [4]

Basic components of the wiper system:

- Front wiper motor and transmission mechanism

- Windshield washer fluid reservoir (with washer motor)

- Wiper and washer control switch

- Relay controlling the rear wiper

Figure 2.2 Wiper and washer system on car

Additionally, some new car models also include:

Structure of wiper and washer system

Figure 2.4 Wiper washer control switch

The car's wiper switch is usually located on the steering wheel, where the driver can easily operate it It is typically positioned to the right and symmetrical to the light control switch The operational modes include:

- OFF: Turns off the wiper

- LO (Low): Operates the wiper at a slow speed, usually used during light rain or when a single wipe is needed

- HI (High): Operates the wiper at a high speed, usually used during heavy rain or when quick wiping is needed

- MIST: Operates the wiper intermittently, only functioning temporarily to remove moisture

Additionally, some vehicles also have a switch to adjust the interval of the wiper in the INT mode In vehicles equipped with a rear windshield wiper, the rear wiper switch is usually arranged together with the front wiper switch To activate the rear wiper, the driver simply needs to move the wiper switch to the middle position between ON and OFF In some modern vehicles, they are also equipped with automatic wipers (Auto mode) and rain sensors, allowing the wiper system to operate automatically without any adjustments from the driver when the switch is set to Auto mode

To control the intermittent wiper mode, most manufacturers use a relay-type control switch, consisting of a circuit with transistors, capacitors, resistors, and relays to form the control circuit This relay circuit receives signals from the control switch and then controls the motor to operate in the intermittent mode

To clean dirt off the windshield, the windshield washer mode is integrated into the wiper switch In newer vehicle models, some manufacturers include a rear windshield washer mode, whereas most older models do not have this feature

The structure of a wiper blade consists of a rubber blade fitted onto a metal bar called the wiper arm The wiper moves in a cyclic motion thanks to the wiper arm Because the wiper blade is pressed against the windshield by a spring, it can wipe away rainwater through the movement of the wiper arm The cyclic motion of the wiper is generated by a motor and a drive mechanism Due to wear on the rubber blade attached to the wiper arm over time, and due to sunlight, temperature, and various environmental factors, the metal inside may become exposed if the blade wears down too much, leading to reduced cleaning effectiveness and potential scratching of the glass Therefore, it is necessary to periodically replace the rubber part of the wiper blade

Figure 2.6 Structure of wiper blade

The wiper motor is a type of DC electric motor with a permanent magnet as the component that creates the magnetic field The wiper motor includes the motor itself and a gear transmission system to reduce the motor's output speed The wiper motor has three carbon brushes for electrical contact: a low-speed brush, a high-speed brush, and a common brush (used for grounding) A cam switch is arranged within the gear system to ensure that the wiper motor always stops at a fixed position

Figure 2.7 Components of wiper motor

A back electromotive force is generated in the armature coil when the motor rotates to limit the motor's rotational speed

Operating at low speed: When the current enters the armature coil from the low-speed carbon brush, a large back electromotive force is generated As a result, the motor rotates at a low speed

Operating at high speed: When the current enters the armature coil from the high-speed carbon brush, a small back electromotive force is generated As a result, the motor rotates at a high speed

Figure 2.8 Working principle of wiper motor

The wiper mechanism functions to stop the wiper arm at a fixed position Because of this function, the wiper arm is always ensured to stop at the bottom of the windshield when the wiper switch is turned off A cam-type switch performs this function This switch has a V- notched cam disc with 3 contact points When the wiper switch is in the LO/HI position, the battery voltage is placed into the circuit, and the current enters the wiper motor through the wiper switch, causing the wiper motor to rotate However, when the wiper switch is turned off, if contact point P2 is in the contact position and not in the notch, the battery voltage is still placed into the circuit, and the current enters the wiper motor to contact point P1 through P2, causing the motor to continue rotating Then, by rotating the cam disc, contact point P2 is positioned in the notch, thus no current enters the circuit and the wiper motor stops However, due to the inertia of the armature, the motor does not stop immediately and continues to rotate slightly As a result, contact point P3 passes the conductive point of the cam disc

The circuit works as follows:

Armature → (+)1 terminal of the motor → wiper switch → S terminal of the wiper motor → contact point P1 → P3 → armature Since the armature generates a back electromotive force in this closed circuit, the motor is electrically braked and stops at a fixed point

Figure 2.9 Front/Rear washer motor

The water reservoir, located in the engine compartment, is typically made from opaque plastic and includes a motor to pump water, housed within the reservoir The windshield washer motor is designed with a fan-like blade, similar to those used in fuel pumps Currently, there are two design types for the rear windshield washing system: one type has a common reservoir for both the front and rear windshield washers, and another type has separate reservoirs for the front and rear systems Additionally, there is a type with one reservoir but two motors for both front and rear Moreover, there is a type that adjusts the spray nozzles for both the front and rear windshields using a windshield washer motor that controls the valves, and another type with two separate motors for the front and rear windshield washer components housed within the reservoir

2.4.2 Combined operation wiper and washer

After turning on the windshield washer switch, after a period, the wiper mechanism will be automatically controlled, referred to as "operation in conjunction with the windshield washer unit." This operation ensures that the windshield washer fluid is sprayed onto the surface of the windshield

Figure 2.11 Combined operation wiper and washer [4]

Working principle of wiper and washer system

3.1 Wiper switch at LOW/MIST position

Figure 2.12 Wiper switch at LOW/MIST position [3]

When the switch is in the Low/Mist position, the current flows to the low-speed of the brushless wiper motor The current travels from the positive terminal of the battery through the Low/Mist control switch, then through the +1 terminal of the wiper motor, and finally returns to the ground

3.2 Wiper switch at HIGH position

Figure 2.13 Wiper switch at HIGH position [3]

When the switch is in the High position, the current flows to the high-speed of the brushless wiper motor The current travels from the positive terminal of the battery through the HIGH control switch, then through the +2 terminal of the wiper motor, and finally returns to the ground

3.3 Wiper switch at OFF position

Figure 2.14 Wiper switch at OFF position [3]

When the switch is moved to the OFF position while the motor is running, the current will flow through the +1 terminal of the motor, and the wiper will slow down The current travels from the positive terminal of the battery through contact P2 of the cam disc, then through the S terminal, then through the switch, then through the +1 terminal of the motor, and finally returns to the ground

3.4 Wiper switch at INT position

Figure 2.15 Wiper switch at INT position when Tr1 activate [3]

When the switch is turned to the INT position, Tr1 will be activated for a short period, causing the relay to move from position A to B At this time, the current from the positive terminal of the battery will flow through the +1 terminal of the wiper motor, which will operate at a low speed

Figure 2.16 Wiper switch at INT position when Tr1 not activate [3]

Tr1 will then quickly turn off, at which point the relay will return to position A and operate similarly to in the OFF mode, causing the wiper to stop wiping After a certain period, Tr1 will be activated again, and the wiper will wipe at a low speed This cycle will be repeated, creating an intermittent wiping mode

3.5 Washer switch at ON position

Figure 2.17 Washer switch at ON position [3]

When the windshield washer switch is turned ON, the current flows to the windshield washer motor: Battery + → windshield washer motor → terminal W → contact point of the windshield washer switch → terminal EW → ground In cases where the wiper is connected to the washer, Tr1 turns on for a predetermined period while the windshield washer motor is operating, causing the wiper to operate at a low speed once or twice The duration Tr1 is on is the charging time for the capacitor in the transistor circuit The recharging time for the capacitor depends on the duration the windshield washer switch is turned on

Some new functions in modern cars today include

4.1 INT function for adjusting the wiper interval

In the INT mode, this function allows the driver to control the interval between wiper operations Depending on whether the rainfall is heavy or light, the driver can adjust the timing between wipes to suit their preference

Figure 2.18 INT function for adjusting the wiper interval [4]

4.2 Function of activating the wipers based on vehicle speed

This feature allows automatic activation of the intermittent operation mode when the wiper switch is in the LO position and the vehicle is stationary, through sensors and the control unit (ECU) When the vehicle stops, moving the wiper control from the INT or HI position to the LO position causes the wipers to operate three times at a low speed and then automatically switch to intermittent mode with an approximate interval of 2.5 seconds When the vehicle is moving and the switch is in the LO position, stopping the vehicle will cause the wipers to operate twice and then switch to intermittent operation with an interval of about 2.5 seconds The timing and control method depend on the market and the specific vehicle model

Figure 2.19 Function of activating the wipers based on vehicle speed [4]

4.3 Automatic wiper function when it rains

When the wiper switch is set to AUTO, this function uses a rain sensor, which is installed on the windshield to detect the amount of rainfall and then sends the information to the control unit (ECU) to optimize the wiper timing based on the rainfall amount

The rain sensor includes the following main components

 Infrared Light: An infrared diode that emits infrared rays through the windshield

 Receiver: A photodiode that receives signals from the infrared diode

 Control Module: Processes signals from the receiver and controls the operation of the wiper system

 Operating Principle of the Rain Sensor

The rain sensor operates based on the principle of detecting changes in light Normally, the infrared diode emits light that then reflects off the windshield and reaches the photodiode When there is no water on the windshield, the infrared light passes through the glass and sends a signal to the receiver The control module receives this signal and determines that the windshield is clean, therefore, the wiper system is not activated

When the windshield is wet, the infrared rays are obstructed and cannot transmit the signal to the receiver The control module receives this signal and determines that the windshield is wet, thus, the wiper system is activated Depending on the amount of light

67 received at the receiver, an appropriate wiper operation signal is transmitted; if there is heavy rain, more water on the windshield means more light is reflected out, resulting in less light received by the receiver

 Safety Function in Case of Malfunction:

If the wiper control component detects a malfunction in the water sensing part, it will control the wiper to operate intermittently appropriate to the vehicle's speed This is a safety function when there is a malfunction in the rain sensor system Additionally, the wiper can also be controlled manually using the wiper switch in the LO and HI positions

1 Presents the most basic structural components of the windshield wiper system

2 Present the steps to identify the 5 pins of a cam-type windshield wiper motor

3 Read the following circuit diagram and explain the operating principle of the circuit diagram in LOW, HIGH, INT, WASHER modes

Figure 2.22 Circuit diagram of wiper-washer system

POWER WINDOW AND DOOR LOCK SYSTEM

Power window system

Today, most car models are equipped with electric power window systems, allowing drivers and passengers to easily control the windows through switches These switches are used to operate the motor in conjunction with some mechanisms of the lifting mechanism inside Unlike in the past, most older car models used manual crank handles

Additionally, the electric power window system is combined with several functions such as:

- Manual lift and lower function: The operator must hold the switch at notch 1 to lift or lower the window, during which the operator can freely adjust the desired window position

- Automatic lift and lower function with a single press: The operator only needs to toggle the switch up or down to notch 2, at which point the window will automatically lift or lower until fully opened or closed

- Window lock function: In this case, the window can only be opened or closed through the driver's control switch

- Anti-jam function: When lifting the window, if an object obstructs the process, the window will automatically stop, then lower slightly to prevent jamming

1.2 Structure of power window system

Figure 3.2 Component of power window system a Window Lifting Mechanism

For the window to move vertically up and down, a lifting mechanism is necessary This component has the capability to convert the rotational movement of the motor into vertical movement Typically, this lifting mechanism includes a scissor-like linkage The window is closed and opened by altering the height of the scissor linkage

Figure 3.3 Window lifting mechanism using scissor linkage

Besides the scissor linkage, some car models are designed with a cable system or a single arm Although the designs vary, the purpose and operating principle remain the same b Power window motor

This is essentially a direct current (DC) electric motor using permanent magnets similar to the motor used in windshield washers and wipers The motor is configured with a switch that can reverse the direction of rotation by reversing the current flow This motor includes three main components: a gear transmission, an electric motor, and an anti-jam sensor Inside the sensor, there is a limit switch and a speed sensor to detect when a jam occurs

Figure 3.4 Components of power window motor

The electric window control switch includes the following functions: it includes a main switch at the driver's side and auxiliary switches at the passenger positions

The main switch functions to:

 Control the entire electric window system in the vehicle

 Control the drive mechanisms for raising and lowering the windows

 Lock the windows and only allow raising and lowering at the driver's position

Figure 3.6 Power window main switch d Passenger power window switch

These are the switches that actuate the motor to control the raising and lowering of the windows at the front and rear passenger positions Each switch can only adjust the window at that specific location and is entirely controlled by the main switch e Electrical lock

The main switch is connected to the electrical lock to receive ON, OFF, and ACC signals to control the window lifting functions when the electrical lock is engaged f Door switch

The car door switch transmits signals to open or close the driver's door (open: ON, close: OFF) to the main electric window switch to control the window functions when the lock is turned off

When the driver toggles the UP switch, a signal is immediately sent from the switch to the IC, at which point the IC will control the transistor Tr to conduct => the UP relay will operate and current will pass through the motor controller => the window will be raised

The operation is similar when in the UP position, where the current will run through the motor in the opposite direction, and the window will be lowered (closed)

1.3.2 Automatic window operation with a single press (Auto)

Figure 3.10 Automatic window operation (AUTO) [3]

When the driver moves the switch up or down two notches (Auto mode), the IC receives the Auto mode signal and controls the window to continue raising or lowering automatically after the driver releases the switch, until it is fully closed or opened

Most modern car models are equipped with an anti-jam function that detects obstacles while the window is being raised This function operates thanks to two main components: the limit switch and the speed sensor, which are fitted within the control motor

The speed sensor has the ability to convert the rotational speed of the motor into pulse form When the window gets jammed, the rotational speed of the motor's belt changes, thereby altering the pulse signal received by the speed sensor (in this case, the pulse width will be longer) The sensor then detects the jam and sends a signal to the limit switch

When a jam signal is received, the limit switch will immediately cut off the UP switch, pause for about 1 second, and then switch to DOWN to lower the window

Figure 3.12 Anti-jam signal from sensor

1.3.4 Power window circuit diagram on Toyota Cressida

Figure 3.13 Power window circuit diagram on Toyota Cressida [1]

When the ignition switch is turned on, there is an immediate positive current from the battery through the relay to power the main control switch (Power window master switch) If the main switch (Main sw) is in the OFF position, the driver will manually control the windows

 Switch in the down position: at this moment (1) will connect with (2), and there will be a current through the motor to lower the window

 Switch in the up position: at this moment (1’) connects with (3’) and (1) connects with (3), there will be a current running back through the motor to raise the window

 Similarly, for other windows through switches S1, S2, S3

When the main switch is closed, passengers can freely control the position of the windows as they wish At this time, there will be current through switches S2’, S3’, S4’ and the operating principle is similar as above.

Door lock system

The car door lock system is one of the most important systems of a vehicle, as it helps protect the car and its contents from thieves and strangers Today's car door lock systems are not only mechanically operated like in the past (inserting the correct key into the lock to open it) Instead, they are controlled and operated by motors and control switches, and are also integrated with a number of functions such as:

Step 1: Only unlocks the door with the inserted key Step 2: Unlocks all remaining doors

- Anti-forgetting-key-in-car function: The car doors cannot be locked with the remote control if the key is still in the ignition

- Safety feature: Once the key is removed from the ignition and the doors are locked

(by remote control or key), the doors cannot be opened using the switch

- Power window control function after ignition is turned off: The power windows can still be operated for a short period of time (about 60 seconds) after the ignition is turned off

- Modern high-end cars even can integrate unlocking into smartphones, unlock by fingerprint or face ID

Figure 3.14 Door lock system on car

2.2 Structure of door lock system

Figure 3.15 Structure of door lock system

 Combined Relay: This is the ECU that controls the door locks, with the function of receiving signals for locking and unlocking the doors, and then sending signals to the respective actuator mechanisms for locking and unlocking

 Warning Switch: Determines whether the key is inserted into the electrical lock It is activated when the key is inserted and deactivated when the key is removed

 Door Lock Assembly: Functions to lock and unlock the doors This is performed when the motor inside receives a signal from the combined relay

Figure 3.16 Components of door lock assembly

An important component in the door lock assembly is the door lock motor, which acts as the executor controlling the locking and unlocking of the door

Figure 3.17 Component of door lock motor

When the door lock motor rotates, torque is transmitted through a screw shaft and gears to the lock position (causing the door to lock), and when the current through the motor is

80 reversed, it will rotate back to unlock After each locking or unlocking action is completed, the gears automatically return to a neutral position thanks to a return spring

This switch functions to determine whether the door has been locked or not When the lock is engaged in the locked position, the switch will turn off (OFF), and conversely, when the lock is engaged in the unlocked position, the switch will turn on (ON), indicating that the door is open

Figure 3.19 Key-operated Unlock Switch

This switch allows the driver to use a key to unlock the car door from the outside

Figure 3.20 Door lock circuit diagram [3]

2.3.1 Control lock/unlock by switch fucntion

Figure 3.21 Control by switch fucntion (LOCK) [3]

When there is a signal to lock the door, the controller immediately controls transistor Tr1 to conduct, activating the locking relay and instantly sending a current through the motor to rotate it to the locked position

Figure 3.22 Control by switch fucntion (UNLOCK) [3]

Similarly, when there is a signal to unlock, transistor Tr2 will conduct, the unlocking relay will activate, and a reverse current will immediately pass through the motor, causing it to rotate back to the unlocked position

2.3.2 Control lock/unlock by using key function

Figure 3.23 Control by using key fucntion (LOCK) [3]

Figure 3.24 Control by using key fucntion (UNLOCK) [3]

The operating principle is similar when controlled by a switch; in this case, the controller receives signals through the key switch

2.3.3 Two step unlocking function (driver door)

When performing the two-step unlocking function, in step 1, pin UL3 will be connected to ground, and only the driver's door will be opened (Transistor Tr2 will not operate) If within

3 seconds unlocking is performed again, the controller will then receive a signal and activate transistor Tr2 to conduct, causing the motor to rotate and the remaining doors to be opened

2.4 Door lock control system using ECU

Figure 3.27 Components of ECU locking system

The components of the lock system controlled by the ECU through the MPX (Multiplex Communication System) network are:

Acts as the central controller of the system

Receives signals from other components to control the door lock status

The car door control switch

The driver's key-operated door lock switch

Sends signals to the Body ECU

Similar to the Door Control ECU, but designated for the front passenger door

Calculates the vehicle's speed based on signals from the sliding control ECU

Sends signals to the Body ECU

Activates the automatic door unlocking function when the airbags deploy to aid in emergency egress

Sends signals to the Body ECU to unlock the doors in case of danger

The system operates as follows:

- When the operator manipulates the door control switch or uses a key to lock the door, the Door Control ECU collects the information and sends a signal to the Body ECU

- The Body ECU processes the information received from the various components and makes the decision to lock or unlock the doors

- When the vehicle is moving at high speed, the system will automatically lock the doors to ensure safety

- When the airbags deploy, the system will automatically unlock the doors to assist in emergency egress

- The door lock control system controlled by the Body ECU in the MPX is also equipped with the following functions: a Automatic Door Unlocking Function in the Event of an Accident

When the airbags deploy, this feature automatically unlocks all doors to facilitate evacuation and emergency assistance in case of emergency b Automatic Door Unlocking by Electric Lock

When the driver's door is closed, turning the ignition from the ON position to the LOCK position and opening the driver's door within about 10 seconds will automatically unlock all the doors c Automatic Door Unlocking Related to the Gear Selector (Optional)

When the ignition is in the ON position, moving the gear selector to the P position from any position will automatically unlock all doors d Automatic Door Locking Related to the Gear Selector (Optional)

The doors of the vehicle will automatically lock if:

- The ignition is turned from the LOCK or ACC to the ON position

- The gear selector is not in the P position

- At least one door is unlocked e Automatic Door Locking Based on Speed

- The doors of the vehicle will automatically lock while the vehicle is in motion if:

- The vehicle speed is greater than 20 km/h

- The gear selector is not in the P or N position

- At least one door is unlocked

Remote door lock control system

Most modern vehicles are equipped with this system, which allows the driver to remotely unlock the doors with just a press of a button, making it more convenient to unlock the doors To achieve this, there must be a signal controller (remote) and a signal receiver installed in the vehicle The remote can be separate or integrated directly into the key

Figure 3.28 Components ofremote door lock control system

Depending on the segment and model of the vehicle, this system may have various functions:

 Lock and unlock functions for doors: Simply pressing the control switch instantly locks or unlocks all doors

 Two-step unlocking function: Similar to key unlocking but only requires operation with a remote

 Feedback function: When pressing the control switch, the hazard warning lights will flash to indicate that the doors have been successfully locked or unlocked

 Trunk or luggage compartment opening function: To execute, simply press and hold the opening switch for about 1 to 2 seconds

 Electric window lifting and lowering function: This feature may or may not be available in some models

 Alarm function: This function activates the anti-theft system, which may or may not be available depending on the model

 Interior light activation function: Interior lights will illuminate for about 15 seconds when the doors are unlocked with the remote

 Automatic door locking function: If no door is opened within about 30 seconds, all doors will automatically lock

 Warning function for unsecured doors: If any door is not fully closed when attempting to lock, an alarm will sound

 Protection function: The control and signal reception unit will be programmed with a security code to prevent interference with other vehicles

 Identification function: In case the controller is lost, it can be reprogrammed through an identification code

The remote door lock control system includes the following main components:

- Remote Control: This is the device that emits signals to lock and unlock doors using radio waves ranging from 300 to 500MHz These devices use lithium batteries and come in two main types: one integrated with the key and one that is separate

- Signal Receiver Control Unit: This unit functions to receive signals from the remote control and sends signals to the combined relay

- Combined Relay: Functions to determine the status of signals received from the receiver and controls the motors for each door to perform locking and unlocking operations

- Key Presence Warning Switch: Determines whether the key is in the electrical lock or not

When the control switch is pressed while all doors are closed and the key is not in the ignition, function codes and identification codes are sent After receiving these signals, the signal receiver will check and assess the status If these codes match the vehicle (to avoid confusion with other vehicles), it will send lock and unlock signals to the combined relay

 Identification Code: consists of 60 numbers including a rotating code that can be changed and an ID

 Function Code: consists of 4 numbers used to operate the system

Figure 3.31 Wiring diagram of the remote unlocking system [3]

When the combined relay receives the signal from the receiver, it will control the transistors Tr1 and Tr2 to operate the motor to perform the locking and unlocking actions

3.3.1 Lock/Unlock operation for all door

After receiving the signal from wireless key, the CPU will send the signal to control the doors to lock/unlock The flow of current in the circuit is same with when unlocking by key

3.3.2 Two step unlocking by wireless key

When performing step 1 of unlocking: At this point, transistor Tr3 will be activated and only current will pass through the driver's door motor, causing the driver's door to open

When performing step 2 within 3 seconds: Transistors Tr2 and Tr3 will conduct and all doors will be opened

3.4 Replace, change key, install new key

Watch the manual video on Mitsubishi Triton model

1 Describe the operating modes of the electric window system and explore the different types of window lifting mechanisms

2 Learn how to replace the battery, erase the key, and program a new key to the smart key system

3 Read the following circuit diagram and explain the operating principle of Door lock and Door unlock modes

Figure 3.36 Door lock circuit diagram

4 Read the following circuit diagram and explain the operating principle of Power Window Up and Down modes

Figure 3.37 Power window circuit diagram [1]

Fu se IG S w it ch

POWER MIRROR, SEAT AND SUNROOF SYSTEM

Power mirror system

The rear view mirror system is a safety feature in vehicles, enabling the driver to observe vehicles behind them and thereby make decisions when driving (such as turning left or right, overtaking, etc.) The rear view mirror system consists of two parts: one flat, rectangular mirror located inside the vehicle, and two exterior rear view mirrors Nowadays, most vehicles are equipped with electrically controlled rear view mirrors These are not only used for observation but also feature additional functions such as automatic mirror folding, mirror position adjustment, safety alerts, etc

The mirror system must meet the following requirements:

 Compact design, easy to control

 Mirrors must provide good reflectivity and visibility

 Ability to fold and unfold (can be operated manually or automatically)

Figure 4.1 Rear view mirror system

2 Exterior Rear View Mirror (Manually controlled type)

6 Exterior Rear View Mirror (Electrically controlled type)

The interior rear-view mirror is mounted above the windshield, rectangular in shape, and has flexible pivot joints allowing the driver to easily adjust it up and down, left and right

The function of this mirror helps the driver to observe directly behind the vehicle In some car models, the interior rear-view mirror also has an anti-glare adjustment lever suitable for day or night conditions

Additionally, this mirror can be designed to integrate with a display, which connects to the rear camera via Bluetooth when the driver shifts into reverse gear Some mirrors are also combined with GPS to provide navigational information

Exterior rear-view mirrors are mounted at the front sides of the car doors Currently, there are three main types:

- Manually controlled type: In this type, the driver needs to use their hand to adjust the mirror up, down, left, or right as desired; this type does not have a folding function

- Electrically controlled type (Motor): This type uses two DC motors to control the mirror adjustments Each mirror has two motors inside (one for left-right control and the other for up-down control) Since they are DC motors, reversing the current will cause the motors to rotate in the opposite direction; thus, one motor is responsible for two actions

For models with a folding function, there is an additional third motor to control the folding

- Remote-controlled by remote: This type also uses motors for control but can be operated remotely This type also features an automatic mirror folding function.

Figure 4.3 Power mirror control switch

The power mirror control switch will include the following functions:

 Mirror selection: The driver can choose the mirror by moving the switch to L (Left) or R (Right)

 Control the mirror up, down, left, right as desired using the control switch

 Automatic folding mirror switch: The driver can fold or unfold the mirrors with just one press This switch may or may not be available depending on the vehicle model Additionally, in some regions with cold weather, some vehicles are also equipped with a heated mirror switch to assist in cases of foggy mirrors

1.3 Power mirror circuit diagram and working principle

Figure 4.4 Power mirror circuit diagram on TOYOTA CELIA 92 [1]

According to the electrical diagram above: Each mirror has 2 motors to control the mirror These two motors share a common terminal, terminal 2 of the electrical connector Terminal 3 of the motor's electrical connector is the other end of the motor that controls the up/down movement, and Terminal 1 of the motor's electrical connector is the other end of the motor that controls left/right movement

The above figure represents an electric mirror type without an automatic folding system For the automatic folding type, there is an additional motor control

Figure 4.5 Power mirror working principle on TOYOTA CELIA 92 [1]

- When the left/right position switch and the mirror control switch are in the OFF position, the 8 pins at the switch connector are disconnected

- When the left/right position switch is OFF, and the control switch is in the UP position, terminals 2 and 3 are connected

- When the left/right position switch is OFF, and the control switch is in the DOWN position, terminals 2 and 1 are connected

- When the left/right position switch is OFF, and the control switch is in the LEFT position, terminals 2 and 3 are connected

- When the left/right position switch is OFF, and the control switch is in the RIGHT position, terminals 2 and 1 are connected

According to the working principle diagram:

- Terminal 2 of the switch connects to terminal 2 of both rear-view mirrors, while terminals 1 and 3 of the switch connect to the power source Thus, when the left/right position switch is OFF, only terminal 2 of the motor's connector is reversed, while terminals 1 and 2 of the motor are open-circuited, and all mirror motors do not operate

- When the left/right position switch is in position L (left), and the mirror control switch is pressed UP, the positive current flows as follows: (+) → 4(machine switch)

→ 3(machine switch) → fuse → 1(mirror control switch) → 7(mirror control switch) → 3(left mirror motor) The negative current: (-) Battery → 3(mirror control switch) → 2(mirror control switch) → 2(left mirror motor) The result is the left up/down motor moves the mirror upwards

- When the left/right selection switch is in the position L (left), and the mirror control is pressed DOWN, the positive current flows as follows: (+) → 4 (machine switch)

→ 3 (machine switch) → fuse → 1 (mirror control switch) → 2 (mirror control switch) → 2 (left mirror motor) The negative current: (-) Battery → 3 (mirror control switch) → 7 (mirror control switch) → 3 (left mirror motor) The result is the left up/down motor moves the mirror downwards

- When the left/right selection switch is in position L, and the mirror control is pressed LEFT, the positive current flows as follows: (+) → 4 (machine switch) → 3 (machine switch) → fuse → 1 (mirror control switch) → 8 (mirror control switch)

→ 1 (left mirror motor) The negative current: (-) Battery → 3 (mirror control switch) → 2 (mirror control switch) → 2 (left mirror motor) The result is the left left/right motor moves the mirror to the left

- When the left/right selection switch is in position L, and the mirror control is pressed RIGHT, the positive current flows as follows: (+) → 4 (machine switch) → 3 (machine switch) → fuse → 1 (mirror control switch) → 2 (mirror control switch)

→ 2 (left mirror motor) The negative current: (-) Battery → 3 (mirror control switch) → 8 (mirror control switch) → 1 (left mirror motor) The result is the left left/right motor moves the mirror to the right

This pattern is similarly followed when controlling the right mirror

Power seat system

Currently, to provide comfort for drivers and passengers, most modern vehicles are equipped with electric seat systems This car seat adjustment system includes mechanisms for raising/lowering, reclining, moving, and sliding

These mechanisms are controlled by buttons or rotary knobs, allowing users to easily adjust the seat to their desired position and angle This system ensures a comfortable and safe seating posture for both the driver and passengers, especially during long trips

2.2.1 Control mode on power seat

Most types of electric seats are equipped with several basic functionalities:

Each of these functions is powered by its own motor control Like the motors used for folding mirrors and raising or lowering windows, these are direct current motors that can reverse their rotation direction by reversing the flow of electricity

Furthermore, in some premium car models, there are systems designed to memorize the adjusted seat positions to accommodate scenarios where multiple drivers use the vehicle and each prefers a specific seat setting

Figure 4.10 Position of control motor on power seat system

Figure 4.11 Power seat control switch

2.2.3 Circuit diagram and working principle

Figure 4.12 Circuit diagram of the TOYOTA electric seat system

Figure 4.13 Power seat circuit diagram on TOYOTA [1]

 FORWARD position: In this setting, pin 1 connects with pin 9 and pin 4 connects with pin 10, moving the seat forward

 OFF position: Pin 1 connects with pins 4 and 10, stopping the seat

 BACKWARD position: Pin 1 connects with pin 10 and pin 4 connects with pin 9, moving the seat backward

Front Vertical Switch (Front elevation):

 UP position: Pin 2 connects with pin 9 and pin 3 connects with pins 5 and 10, raising the driver's seat

 OFF position: Pins 2, 3, and 5 connect together, stopping the driver's seat

 DOWN position: Pin 2 connects with pins 5 and 10, and pin 3 connects with pin 9, lowering the driver's seat

Rear Vertical Switch (Rear elevation):

 UP position: Pin 6 connects with pin 9, and pin 7 connects with pins 8 and 10, raising the rear seat

 OFF position: Pins 6, 7, 8, and 10 connect together, stopping the rear seat

 DOWN position: Pin 6 connects with pins 8 and 10, and pin 7 connects with pin 9, lowering the rear seat

 FORWARD position: Pin 5 connects with pin 9 and pin 8 connects with pin 10, tilting the seat forward

 OFF position: Pins 5, 8, and 10 connect together, stopping the seat

 BACKWARD position: Pin 5 connects with pin 10 and pin 8 connects with pin 9, tilting the seat backward

2.4 Memory mode for seat adjustments in newer car models:

The operating principle of this feature is quite simple A variable resistor is connected to the motor, and it moves in conjunction with the seat motor After the seat adjustment is completed and saved, the position of the variable resistor is also saved This principle is similarly applied in some models to remember the position of the mirrors

Figure 4.14 Power seat controlled by Micro-Computer on Mazda [13]

Power sunroof system

The concept of the sunroof first appeared in the 1920s, initially available only on luxury vehicles Today, most car manufacturers offer models with sunroofs, catering to consumer preferences Depending on the design, there are various types of sunroofs: sliding type, manually operated, and electrically controlled via motors and switches

The construction of the sunroof system includes several main components:

 Glass: This glass is tempered, similar in structure to a windshield, and allows light to enter the vehicle Typically, this glass is designed to minimize UV rays

 Sliding tracks/slots: These metal tracks enable the sunroof panel to slide in and out

 Motor: Like electric seats or mirrors, the sunroof uses motors for automatic sliding

 Control switch: This switch may be located on the driver's door or other locations depending on the car manufacturer’s design

 Drainage system: Includes channels and pipes to drain water away from the sunroof to prevent leaks

 Sunshade: A fabric panel that can be pulled over the glass to provide shade

 Stop switch: Limits the stopping position of the sunroof

Figure 4.16 Sunroof components on mazda [13]

3.3 Circuit diagram and working principle

Figure 4.17 Power sunroof circuit diagram on mazda [13]

In terms of operating principles, the sunroof system is quite similar to the electric window system, both relying on the principle of reversing the electric current to the motor to change the direction of rotation, thereby allowing the door to open and close

Based on the circuit, the Mazda sunroof system is electronically controlled through a CPU and has two relays connected to both ends of the motor The driver controls the opening and closing of the window through a switch The switch sends a signal to the CPU, and the CPU controls the motor There are three control modes:

 Tilt up: In this mode, the window glass tilts up at a certain angle to allow air into the vehicle without fully opening the sunroof

Figure 4.18 Working principle at tilt up mode [13] o When the sunroof switch is operated to tilt up, the CPU receives the tilt-up signal (1) from the control switch o Upon receiving the tilt-up signal, the CPU immediately activates sunroof relay number 2 (2) o When sunroof relay number 2 is activated, the sunroof motor begins to rotate to control the tilting up operation (3) o About 1 second after the sunroof motor starts, the CPU's timer control will automatically turn off sunroof relay number 2 to stop the tilting up operation

3.3.2 Working principle at open mode

Figure 4.19 Working principle at open mode [13] o When the sunroof switch is operated to open, the CPU receives the open signal (1) from the control switch o Upon receiving the open signal, the CPU immediately activates sunroof relay number 1 (2) o When sunroof relay number 1 is activated, the sunroof motor begins to rotate to control the opening operation (3)

3.3.3 Close mode while operating at tilt up mode

Figure 4.20 Working principle at close mode while tilting up [13] o When the sunroof switch is operated to close, the CPU receives the close signal (1) from the control switch o Upon receiving the close signal, the CPU will turn off sunroof relay number 1 (2) o When sunroof relay number 1 is turned off, the sunroof motor begins to rotate to control the closing operation (3)

3.3.4 Close mode while operating at open mode

Figure 4.21 Working principle at close mode while opening [13] o When the sunroof switch is operated to close, the CPU receives the close signal (1) from the control switch o When the CPU receives the close signal while in the open mode, it will activate sunroof relay number 2 (2) o When sunroof relay number 2 is activated, the sunroof motor begins to rotate to control the closing operation (3)

Figure 4.22 Power sunroof circuit diagram on Toyota Camry [4]

1 Present how to identify the pins of the mirror control switch, and redesign the mirror control circuit to include automatic folding

Figure 4.23 Power mirror control SW

2 Present how to identify the pins of the power seat control switch

Figure 4.24 Power seat control SW

3 Collect and explain the electrical circuits of sunroof systems from various car manufacturers

Figure 4.25 Circuit diagram of power mirror

4 Read the following circuit diagram and explain the operating principle of power seat each modes)

Figure 4.26 Circuit diagram of power seat

INFORMATION SYSTEM

Analog information

Analog information in cars usually relates to how data and information are displayed or communicated through devices and systems that do not use digital technology, through various gauges and control panels that use clock hands and dials

Figure 5.3 Circuit diagram of tableau with analog information [1]

2.1 Oil pressure gauge and oil pressure sensor

The oil pressure gauge indicates the oil pressure in the engine, helping to identify issues in the lubrication system Typically, this gauge is designed as a dual needle This component includes two main parts: an oil pressure sensor, usually mounted in the engine's cylinder area or at the oil filter, and a display gauge, placed on the dashboard in front of the driver Both the gauge and the sensor are connected together and also connected to the electrical circuit through the ignition switch

The task of the sensor is to convert the change in oil pressure into an electrical signal, which is sent to the gauge The oil pressure gauge displays based on the electrical signal received from the sensor, with the scale divided into units of kg/cm^2 or bar

Currently, on cars, four types of oil pressure gauges can be found: thermal, magnetic, mechanical, and electronic Among these, only the thermal and magnetic types are detailed here

Figure 5.4 Thermoelectric Oil Pressure Gauge [1]

When an electric current flows through a component made from combining two metals or alloys with different thermal expansion coefficients (a bimetallic element), it causes the component to bend as the temperature increases The gauge uses such a bimetallic element, linked to a spring, to perform its function The shape of this bimetallic component is described in Figure 5.5 The bending of the bimetallic element, caused by environmental temperature changes, does not result in any discrepancy in the gauge's indication

Figure 5.5 Operation of the Bimetallic Element [1]

In the oil pressure measuring component, the bimetallic element is equipped with a contact point The movement of the needle on the gauge is directly proportional to the electric current through the spring When there is no oil pressure, the contact point will open, not conducting electricity when the ignition switch is turned on, hence, the needle does not move

When the oil pressure is low, the contact point moves slightly due to the push of the membrane, allowing electric current through the sensor's spring Because of the weak contact force, the contact point will reopen as the bimetallic element bends due to the generated heat The contact point opens and interrupts the current only briefly, not causing the temperature of the bimetallic element on the gauge to rise significantly, therefore, it only bends slightly As a result, the needle only deviates slightly

Figure 5.6 Operation of the Thermoelectric Gauge under Low/Small Oil Pressure [1]

Figure 5.7 Operation of the Thermoelectric Gauge under High Oil Pressure [1]

When the oil pressure is higher, the membrane push increases the force on the bimetallic element, causing it to lift As a result, the electric current is maintained for a longer period The contact point only closes when the bimetallic element bends upwards The electric current will continue to flow through the oil pressure measuring component until the contact point of the oil pressure sensor opens, leading to an increase in temperature and bending of the bimetallic element at the measuring component, causing the gauge needle to move significantly Therefore, the movement of the gauge needle reflects the change in bending of the bimetallic element in the oil pressure sensor

2.1.2 Magnetic Electric Oil Pressure Gauge

The construction of the magnetic electric oil pressure gauge is shown in Figure 5.8

Figure 5.8 Structure of Magnetic Electric Oil Pressure Gauge [1]

Annotations for the construction of the magnetic electric oil pressure gauge:

1 Pressure chamber 11 Copper contact leaf

6 Lever arm 16 và 20 Permanent magnet

10 Resistor coil of the variable resistor

Rcb Sensor resistance The total magnetic flux and the position of the gauge needle correspond to different positions

When the switch is turned off, the needle on the gauge returns to the 0 position The position of the needle is maintained by the magnetic force interaction between two permanent magnets, number 16 and 20 When the switch is activated, the electric current begins to flow through the coil in both the gauge and the sensor in the direction indicated in Figures 5.8a and 5.8c The intensity of the current and the magnetic flux through the coils are determined by the position of the sliding component on resistor number 10 The maximum current that can be achieved in the circuit of the gauge and sensor is 0.2A

When the pressure in chamber number 1 of the sensor is P = 0, the sliding component number 8 is positioned extremely to the left of resistor number 10, as illustrated in the figure, meaning the resistance Rcb reaches its highest value As a result, the current through coil W1 is at its highest, while at coils W2 and W3, it is at its lowest The magnetic fluxes Φ1 from coil W1 and Φ2 from coil W2 counteract each other, hence the value and direction of the magnetic flux are determined by the difference Φ1 - Φ2

The magnetic flux Φ3, generated by coil W3, interacts with the difference in magnetic flux Φ1 - Φ2 at a 90-degree angle

The total magnetic flux ΦΣ of the three coils is determined by the vector addition rule ΦΣ will dictate the direction and rotational position of magnet disc number 16, and thereby determine the position of the needle on the gauge scale When the switch is turned on and the pressure in chamber number 1 is 0, the total magnetic flux ΦΣ will orient the magnet disc so that the needle points to 0 on the scale When the pressure in chamber number 1 increases, membrane number 4 bends further, causing lever number 6 to rotate around its axis The lever, via screw number 7, impacts the sliding component number 8, causing it to move to the right This leads to a decrease in the resistance value of the resistor (Rcb), thereby increasing the current intensity through coils W1 and W2 as well as the magnetic flux Φ1 - Φ2 that they produce Simultaneously, the current intensity and magnetic flux Φ3 from coil W3 decrease

In this case, the value and direction of the total magnetic flux ΦΣ change, causing the position of magnet disc number 16 to change and the gauge needle to move toward higher pressure values

When the pressure P = 10 kg/cm², the sliding component moves to the ultimate right position of resistor number 10, meaning the resistance of the sensor Rcb drops to 0 (the resistor

127 is short-circuited), causing coil W1 to also short-circuit and the current through this coil to drop to 0, moving the gauge needle to the right of the scale

The fuel gauge informs the driver about the current level of fuel (gasoline or diesel) in the tank There are two types of fuel gauges: one that uses a bimetallic resistor and another that uses a cross-coil

A bimetallic component is installed at the gauge display, while a fuel level sensor uses a float-type variable resistor This variable resistor has a float that moves according to the fuel level, with the sensor body attached to a slideable variable resistor, and a float arm connected to the variable resistor The movement of the float changes the position of the contact point on the variable resistor, resulting in a resistance change The standard position of the float can be set at a high or low level in the tank, with the low position offering greater accuracy as the fuel level decreases, hence it is commonly preferred in digital display gauges with a large measuring range

When the ignition switch is turned to the ON position, electricity flows through the voltage regulator and through the heating wire of the fuel gauge, then it grounds through the slideable variable resistor of the fuel level sensor The heating wire in the gauge generates heat due to the electric current passing through it, causing the bimetallic element to bend depending on the intensity of the current As a result, the needle linked to the bimetallic element moves to a certain angle

Figure 5.9 Float-Type Sliding Variable Resistor Fuel Level Sensor [1]

When the fuel level in the tank is high, the variable resistor has a low resistance, leading to a high current intensity passing through it Consequently, the heating wire in the fuel gauge generates more heat, causing the bimetallic element to bend significantly and pull the gauge

Digital information

Figure 5.25 VFD Dashboard in TOYOTA Vehicles [1]

The digital display on each gauge typically uses a VFD - Vacuum Fluorescent Display, some LED lights, or an LCD - Liquid Crystal Display The VFD type is commonly used in digital display gauges in newer vehicle models Digital display gauges have the following features:

 High reliability due to the digital display, with no moving parts

 Optimal display for each gauge Below is a description of the VFD electronic dashboard in the TOYOTA CRESSIDA

It includes 20 small fluorescent segments used in the vehicle speed gauge to display speed numerically The vacuum fluorescent display operates similarly to a triode tube and consists of three parts:

 20 segments (anodes) coated with a fluorescent substance

 A grid placed between the anode and cathode to control the current

All these components are installed in a flat glass chamber, which has been completely evacuated The anode is mounted on the glass plate, and the wires connecting to the anode are placed directly on the surface of the glass plate An insulating layer is applied to the glass plate, and the parts containing the fluorescent substance are placed on this insulating layer

The parts covered by the fluorescent substance light up when struck by electrons Above the anode is a control grid, made from a special type of metal, and above this grid is the cathode, consisting of a series of thin tungsten wires coated with a material that emits electrons when heated

Figure 5.26 Construction of Vacuum Fluorescent Display (VFD) [1]

When current flows through the filaments, they are heated to about 600°C, thereby emitting electrons

Figure 5.27 Vacuum Fluorescent Display (VFD) [1]

When positive voltage is applied to the fluorescent segments, it attracts electrons from the tungsten (filament) wires These electrons then move into the fluorescent segments, then to the negative pole (ground), and finally back to the tungsten wires, completing a cycle

When the electrons from the tungsten wires collide with the fluorescent segments, the fluorescent material is excited and lights up, which only occurs when positive voltage is provided to the segments Without the positive voltage, the segments do not light up

The special metal grid plays a crucial role in ensuring that electrons are evenly distributed across all the fluorescent segments Since the grid always maintains a positive voltage, it attracts electrons emitted from the tungsten wires Thus, as the electrons pass through the grid and continue their journey to the anode, they are evenly distributed

The use of LEDs as a display component has the drawback of consuming a large amount of electric current For this reason, liquid crystal displays (LCDs) are now widely preferred

An LCD is a type of optoelectronic semiconductor component

In ordinary liquids, molecules are arranged in a disordered manner However, in liquid crystals, the molecules are organized in an oriented way When an electric field is applied to a liquid crystal, its elliptically shaped molecules align in a specific order Consequently, when light is shone on the liquid crystal without any electric current, the light passes through without being reflected, making it invisible to us However, when electric current is passed through the liquid crystal, the conducting particles collide with the molecules, causing their arrangement to become chaotic and disordered As a result, the incoming light is scattered, causing the liquid crystal to light up and become visible to the eye

Figure 5.28 Information system circuit diagram on TOYOTA CRESIDA [1]

Overview of communication networks in automobiles

Today, most car manufacturers integrate communication networks into their information transmission systems The communication network in cars is simply a system that facilitates interaction among various control units within the same vehicle, including types such as ECM, TCM, BCM, ABS, etc These can exchange information without the need for an extensive number of wires, which optimizes control and reduces wiring

With the continuous development of automotive technology, an average European car now has about 30 different control units, and in luxury cars, the number of control units can increase to hundreds Even systems like seat controls, trunk opening, or audio controls all have their own control unit connected via a communication network For example, the TCM control unit can take engine speed signals and throttle pedal signals to adjust the gear appropriately, and the vehicle speed displayed on the dashboard might come from the transmission control unit or the ABS control unit

To meet requirements for safety, convenience, and high precision, each control unit must be linked to exchange information quickly, timely, and accurately The current automotive communication networks are the optimal solution to address these issues The advent of communication networks has helped reduce the number of wires to a minimum, increased accuracy in information processing, and reduced costs in manufacturing a vehicle

Common communication protocols in Automobiles today include:

 CAN (Controlled Area Network): A widely used multipoint communication protocol that provides a linking mechanism between control units without needing individual point configuration

 LIN (Local Interconnect Network): A simpler communication protocol than CAN, designed to save costs for independent and interrelated control units

 MOST: An optical port-based communication protocol providing a multipoint linking mechanism for entertainment devices and control systems in vehicles

 FlexRay: A multipoint communication protocol with high safety and accuracy features, used for complex automotive control systems

 Additionally, other protocols like J1979, J1850, ISO 9141, K-line, etc., exist However, with the development of autonomous vehicles, the data volume and transmission speed must be very high to ensure driver safety High-precision networks like CAN and FlexRay that are widely used today may not meet these requirements Therefore, developing protocols like Ethernet TSN (Time-Sensitive

Networking) and Ethernet AVB (Audio Video Bridging) might be used to address these issues in the future

Data transmission speed measures the volume of data transmitted in a unit of time The bit is the smallest unit of data, and data transmission speed is typically measured in bits per second Other terms such as transfer rate, data rate, bit rate, and baud rate all convey the same meaning The speed requirements vary depending on the specific application Fast transmission speeds create more pressure on development and increase costs, while slow speeds encounter issues with bandwidth density and transmission delays

This requirement mainly relates to the issue of noise in information transmission Ideally, transmitted data would be completely noise-free or loss-free However, in reality, the data transmission environment in cars is complex and affected by the engine and other electrical systems, making complete noise elimination nearly impossible Thus, minimizing the impact of noise on communications is a top priority, and the system's noise resistance depends on the level of safety and purpose it serves

This feature requires high accuracy in time (transmission time and response time), where the time deviation is very small compared to other systems Real-time requirements are only present in some specific systems and often come with high reliability demands such as brake systems, airbags, etc

4.3.4 Number of nodes in network

Limiting the maximum number of nodes in a communication network brings significant implications:

 Addressing transmission delays: Reducing the number of nodes in the network decreases the likelihood of message overlap, thus reducing transmission delays

 This limit allows the use of a single protocol within the vehicle's internal network, ensuring compatibility and cost savings compared to using multiple different protocols

 Efficient management and development: Limiting the maximum number of nodes helps nodes operate more efficiently and manageably and facilitates research and development

In fact, the maximum number of nodes in a protocol is determined based on the purpose of the protocol and the acceptable transmission delay for that protocol's speed

Generally, the internal network in cars is classified into three main groups based on their function and characteristics:

- Transmission and chassis systems need to consider real-time requirements (most systems in these two groups require this characteristic)

- Interior control partition systems (related to comfort features) typically have a large number of nodes, distributed throughout the vehicle, so multi-channel operation capability is crucial

- Multimedia and entertainment systems need to focus on bandwidth and data transmission speeds because the information transmitted in this group often involves images, sound, or video

Currently, the trend in the automotive industry is to replace old mechanical and hydraulic systems with computer-controlled mechatronic systems Systems such as ABS, TCS, VSC, etc., require electronic control systems to achieve precision and stability; therefore, the protocols used must be continuously improved and replaced with newer and more efficient ones

As mechanical-hydraulic systems are replaced with mechatronic systems, the number of control computers will increase, and because these structures operate within the engine compartment, these computers must also be located there The engine compartment is one of the areas most susceptible to electromagnetic interference in the vehicle, so the systems must have robust noise interference mechanisms to ensure stability in communication

The networks in this application group have two protocol classes suitable for use:

- Class C: commonly used in real-time applications in vehicles, as many mid-range and luxury vehicles use this protocol group

- Class C+: used less frequently and primarily applied in advanced X-by-wire systems, including diesel engine control (EDC), power transmission control, vehicle dynamic control (ESP), automotive chassis control systems (ABS), and adaptive cruise control systems (ACC)

For both groups, they feature real-time capabilities and meet the requirements for interference resistance

This is arguably the most complex and node-dense application area in vehicles The nodes in this array are not just control computers but also include buttons, switches, indicator lights, and are often arranged in clusters scattered throughout the vehicle

A few typical systems might include:

- Access control with anti-theft alarm devices

- Door modules (automatic window control, mirror adjustment)

These systems in this group still require real-time performance but are not overly strict and typically do not require high speeds, focusing instead on the number of nodes allowed in a network Due to the characteristics described above, protocols in groups A and B are most suited for this type of application; however, in some vehicle models, protocols from group C may still be used Typically, both groups A and B are used concurrently:

- Class A is used to link control computers with buttons, switches, etc

- Class B is used to connect control computers from different clusters

Multimedia applications in vehicles may include:

The design of this type of network typically focuses on a central area with a display screen and corresponding control units

This is also a highly differentiated network with two protocol groups that differ significantly in speed: Class B and Class D

- Class B is used for control-oriented networks such as indicators, buttons, and disc changers

- Class D is used for high-quality image, sound, and video transmission applications, and sometimes also includes voice control, 360-camera signals, and internet.

CAN Communication network

CAN is a communication protocol developed in the 1980s by Bosch to support real- time distributed control systems with extremely good stability, security, and noise resistance Today, besides the automotive sector, CAN is also widely used in industries such as automation, shipbuilding, submarines, agriculture, and medicine due to its high reliability

A node is an independent component that can transmit and receive data on a CAN bus

A node includes an MCU, a CAN controller chip, and a CAN transceiver chip Nodes within the CAN network can exchange data through the transmission and reception of data known as messages Each node can receive several different types of messages

On the CAN bus, information is sent in messages with a fixed format and limited length (number of bits) When the bus is idle, any node can begin transmitting a new message Messages are transmitted in four different frame types: data frame, remote frame or control frame, error frame, and overload frame

In a specific system, the bit rate on the CAN interface is uniform and fixed, but it can vary in different systems The bit rate also depends on the length of the transmission The maximum speed can reach up to 1 Mbit/s Below is a reference table:

(Bit Rate – kbit/s) (Bus Length - m) (Nominal Bit-time - às)

During operation, the bus can hold two logical values: "dominant" (corresponding to bit 0) and "recessive" (corresponding to bit 1) If both "dominant" and "recessive" signals are transmitted on the bus at the same time, the bus value will be "dominant" This is the AND- wire operation of the bus

5.2 Characteristics and requirements of CAN

Each data frame or request is assigned an IDENTIFIER (called an ID) This ID determines a fixed priority level for each message throughout the bus access process Whenever the bus is idle, any Node can start sending messages However, if two or more Nodes transmit messages at the same time, a bus access conflict occurs To avoid this, the bit arbitration mechanism of the ID is used to ensure that data is not lost and no transmission time is wasted During arbitration, the losing Node will stop, and its message will be resent after the bus is free No time is lost because the arbitration occurs in real time; the winning Node will continue to send the remaining bits without needing to stop and resend from the beginning

A Node waiting for data can request another Node to send a corresponding data frame by sending a request frame The IDENTIFIER of the data frame and the request frame must match

If the bus is idle, any Node can send a message, but only the Node with the highest priority can gain access to the bus, so its message is transmitted first Messages from other Nodes must temporarily pause and wait to continue transmission

For safety in data transmission/reception, the protocol provides regulations for error detection, signaling, and checking for each CAN node Error detection mechanisms include:

 Monitoring: Comparing the bit level transmitted with the bit level on the bus

 Using Cyclic Redundancy Check (CRC) codes

 Frame checking The probability of undetected errors is extremely low, at (Message error rate): 4.7×10 −11

CAN is a communication protocol characterized by address-based and object-oriented communication methods Unlike most other bus systems, it uses an ID attached to each piece of information exchanged in the network Information is transmitted in messages of varying lengths and can be received by any node on the network instead of being sent to a specific address The ID of each message only indicates the content of the data sent, not a specific destination Therefore, each node can decide to accept or ignore the information by a selective method Multiple nodes can also receive a single message and react differently A node can request another node to send data by sending a request frame A CAN node can return a data frame with the same ID as the request frame, providing the requested information content The flexibility and data consistency are ensured by the object-oriented communication mechanism of the CAN network The CAN bus does not need to know the system configuration (specifically, the node addresses), allowing for the addition or removal of nodes without changing hardware or software at other nodes In the CAN network, messages can be received by all interested nodes or by no nodes at all Data consistency is ensured through simultaneous message sending and error handling

The first standard of CAN is ISO 11898, which defines the characteristics of CAN, including both high-speed and low-speed CAN Low-speed transmission: CAN-C is defined in the ISO 11898-2 standard and operates at speeds from 125kbit/s to 1 Mbit/s, allowing for precise real-time data transmission Therefore, the CAN-C bus is used in systems like engine control, power transmission control, vehicle stability systems, etc High-speed transmission: CAN-B is defined according to the ISO 11898-3 standard and operates at bit rates from 5 to 125kbit/s It is used in many applications within the vehicle body, providing comfort to users This speed ensures real-time requirements within this range Examples include applications like air conditioning control, seat adjustment, automatic window control, sunroof slide adjustment, mirror adjustment, lighting systems, and steering control systems

Figure 5.30 Function of CAN communication layers [9]

ISO 11898 generally defines two layers: the Physical Layer and the Data Link Layer within the 7-layer OSI model, where:

- The Physical Layer specifies the representation and identification of bits 0 and 1, timing, and synchronization It includes physical components such as wires and voltage for transmitting information

- The Data Link Layer includes Logical Link Control and Media Access Control (MAC) to define the transmission frame and priority rules ISO 11898 also defines mechanisms related to error checking and handling, including five types of errors: bit errors, bit stuffing errors, CRC errors, frame format errors, and ACK errors

5.3.2 Components and signals in the CAN bus a CAN network components

The CAN network includes the following basic components:

- The CAN bus wires consist of two separate wires: CAN_H (CAN High) and CAN_L (CAN Low) Twisted pair or optical cables may be used depending on the application

To reduce interference, the cables are also shielded and connected to a reference voltage or GND When the bus is not transmitting data, the voltage on CAN_H is usually 0V, and on CAN_L, it is typically +5V The CAN bus is a differential bus, so when data is transmitted on the bus, the voltages on CAN_H and CAN_L will change, thereby determining the logic levels 0/1 based on the voltage difference between CAN_H and CAN_L

- The line termination resistors are 120Ω

- Node: is the component connecting the two CAN wires and includes: MCU, CAN controller, and CAN transceiver Where: o Microcontroller (MCU): is a control device responsible for operating the CAN Controller and distributing the data to be transmitted to the CAN Controller It also receives data from the CAN Controller for use in Node operations o CAN Controller: Executes data transmission and reception operations, handles errors, calculates bit timing according to the CAN standard, and outputs digital data (in logic levels 0/1) via the TX pin It also receives digital data via the RX pin o CAN Transceiver: Converts the digital signal (logic levels 0/1) on the TX pin into an analog signal on the CAN bus and vice versa, converting the analog signal on the CAN bus (CAN_H and CAN_L) into a digital signal on the RX pin

Figure 5.31 Bus Structure and Node of the CAN Network b Signals on the CAN bus

The CAN Transceiver converts from digital to analog signals and vice versa to communicate with the CAN controller and the CAN bus In the CAN protocol, high-speed CAN typically has:

 "Dominant" level, which acts as logic level 0

 "Recessive" level, which acts as logic level 1

Figure 5.32 Voltage on CAN_H and CAN_L when transmitting high-speed CAN data

The voltage on CAN_H and CAN_L when transmitting high-speed CAN data The CAN bus operates on an AND-wire mechanism, so when both logic 0 and logic 1 are transmitted from the CAN controller via the CAN transceiver to the CAN bus at the same time, logic 0 will dominate on the CAN bus The voltage on the CAN bus operates in a range from -2V to +7V, but typically at 0V and +5V when operating at a high speed of 1Mbit/s CAN_H has a voltage of +5V when idle, which drops to +3.5V when active, where +3.5V is considered the

"dominant" level and +2.5V is the "recessive" level Similarly, CAN_L has a voltage of 0V when idle, which rises to +1.5V when active, where +1.5V is considered the "dominant" level and +2.5V is the "recessive" level

Figure 5.33 The difference of logic voltage level between CAN_L and CAN_H

Determining the logic voltage level through the difference between CAN_L and CAN_H The bus state is determined by the voltage difference between CAN_H and CAN_L

LIN communication network

LIN (Local Interconnect Network) is a communication network widely used after CAN This network is typically used internally within the body system and does not require high transmission speeds, and it supports bidirectional communication The LIN network is often used in "Sub systems" such as seat controls, mirror controls, sunroofs, door locks, window lifts, etc

In the past, parallel computer systems used different local networks to connect processing nodes However, the use of these networks did not yield positive results, was not efficient, and caused many limitations to the usability and scalability of the system The LIN communication network was developed to address these limitations and is also an effective replacement solution for the CAN protocol to optimize cost

Figure 5.52 LIN network communication arragement

Typically, the LIN communication network is designed with either a star or mesh structure

Star structure: There is a central node or controller located at the center of the network All other processing nodes are directly connected to the central node through communication channels Each processing node can communicate directly with the central node and send or receive messages from other nodes without going through the central node Therefore, the central node plays an important role in coordinating communication between nodes

Mesh structure: Consists of a collection of processing nodes connected to each other through point-to-point connections Processing nodes can communicate directly with each other without going through a central node if it is a point-to-point connection The mesh

165 structure creates a tightly interconnected network, allowing messages to be transmitted from any node to any other in the system

The structure of the LIN communication network is designed to optimize performance and scalability Through the use of point-to-point connections and features such as multipath and swap operation, the LIN network can provide effective communication between processing nodes and meet the requirements of parallel applications LIN is a broadcast serial network comprising 16 nodes (one master and typically up to 15 slaves) All messages are initiated by the master with at most one slave responding to a given message ID The Master node can also act as a slave by responding to its messages Because all communication is initiated by the Master, the Master does not need to perform collision detection

Master and slave are usually microcontrollers but may be implemented in dedicated hardware or ASIC to save costs, space, or energy

The current use combines the low cost of LIN and simple sensors to create small networks These subsystems can be connected by a backbone network (i.e., possible in cars))

The LIN bus is a bus visited with one master device and one or more slave devices The master device contains both the main task and the subtask Each slave device contains only one slave task Communication over the LIN bus is entirely controlled by the main task in the main device The basic transmission block on the LIN bus is a frame divided into Header and Response The header is always transmitted by the master node and includes three separate parts: break, sync, and identifier (ID) The response, transmitted by a slave task and may be in the master node or slave node, includes the data payload and checksum

Typically, the master task polls each slave task in a loop by transmitting a header, including the break-sync-ID sequence Before starting LIN, each slave task is configured to publish data on the bus or subscribe to data to respond to each received header ID When a header is received, each slave task verifies the parity of the ID and then checks the ID to determine whether it needs to publish or subscribe

- If a slave task needs to transmit a response, it will transmit one to eight bytes of data to the bus, followed by a checksum byte

- If a slave task needs to subscribe, it will read the data payload and checksum byte from the bus and perform the appropriate internal action

For standard slave-master communication, the master emits an ID to the network, and only one slave responds with the data payload Communication from master to slave is performed by a separate slave task within the master node This task automatically receives all data published on the bus and responds as though it is an independent slave node To transmit data bytes, the master must first update the response of the internal slave task with the data

166 values it wants to transmit Then, the master publishes the appropriate header frame, and the internal slave task transmits its data payload to the bus

 Break: Every LIN frame starts with a Break, consisting of 13 “dominant” bits followed by a one-bit break signal This part serves as a frame start notification for all nodes on the bus

 Sync: is the second field transmitted by the master task in the header Sync is defined as the character x55, which allows slave devices to perform automatic baud rate detection to measure the transmission rate interval and adjust their internal transmission rate to synchronize with the bus

 ID: is the last field transmitted by the master task in the header The ID provides identification for each message on the network and determines which node in the network should either publish or respond each transmission All slave tasks continuously receive the ID fields, verify their parity, and determine whether their role is to publish or subscribe with this specific ID information The LIN bus provides a total of 64 IDs, with IDs from 0 to 59 used for signal-carrying frames, 60 and 61 for carrying diagnostic data, 62 reserved for user-defined extensions, and 63 reserved for future protocol enhancements The ID is transmitted over the bus as a protected one-byte ID, with the lower six bits containing the raw ID and the upper two bits containing parity

 Data byte: is transmitted by the slave task in the response, this field contains from one to eight bytes of data payload

 Checksum: is transmitted by the slave task in the response The LIN bus defines the use of one of two checksum algorithms to compute the value in the 8-bit checksum field The classic checksum is calculated by summing the data bytes, and the enhanced checksum is calculated by summing the data bytes and the protected ID

 Point-to-Point connection: The LIN communication network uses point-to-point connections between processing nodes This allows each processing node to be directly connected to a few other nodes without going through a central node Using these point-to-point connections helps to minimize latency and increase message transmission efficiency, meaning information is transmitted quickly

 Addressing system: The LIN communication network uses an addressing system to identify processing nodes within the network Each node is assigned a unique address, allowing it to send and receive messages from other nodes in the system

 Communication protocol: The LIN communication network uses communication protocols to manage the sending and receiving of messages between nodes These protocols ensure the accurate, synchronized, and reliable transmission and reception of data over point-to-point connections

 Error management: The LIN network incorporates error management functions to detect and handle errors during communication This ensures that messages are sent and received reliably

AIR CONDITIONING SYSTEM

STATISTICS AND REPAIR OF ALL TRAINING MODELS

USER MANUAL, PRACTICE SHEET AND SELF-LEARNING

CONCLUTION AND RECOMMENDATION