NHÓM – LỚP Đ8-ĐTVT - LƯƠNG NGỌC LONG HỒNG NGỌC TRUNG HỒNG THỊ LINH NGƠ ANH TUẤN PHÙNG THỊ QUỲNH PHẠM TRỌNG HOAN MSV: 1381510142 MSV: 1381510176 MSV: 1381510140 MSV: 1381510179 MSV: 1381510165 MSV: 1381510127 Lesson 5: Alarm Systems Task 2: This diagram show a circuit of alarm systems There are detection devices: door switch, windows foil, pressure mat and passive infra-red detector The warning device is the bell Because, it protects the alarm system If the door is opened, the window is broken, when someone step on the pressure mat or when someone moves on motion sensors range, the bell will ring When a burglar disconnects the supply, this system won’t work Task 3: Door switch: magnetic switches Window foil: break detectors Pressure mat: pressure mats Passive infra-red detector: motion sensors Task 4: We can make window foil more effective by adding a low current electric which can't kill but it will bring pain when someone touches it directly if the window is broken to prevent thief or burglar try to break in your house Task 5: 2-e Action A burglar disconnects the supply The glass is broken Consequence The alarm continues to operate on batteries The foil breaks too 3-f A door is opened 4-a A window is opened A magnet on the door trips a switch on the frame A magnet on the moving part trips a switch 1-c Device Battery backup Break detectors Magnetic switches Magnet switches 5-g 6-b 7-d You’re not there to reset the system A burglar tries to force the alarm open Someone steps on them The alarm stops after a set time Tamper sensors trigger the alarm Two thin metal plates come in contact Automatic cutoff Tamper protection Motion sensors Task 6: If pressure mats are constantly walked on, two thin metal plates will come in contact If you fit an exit delay, you won’t set off the alarm when leaving the house If your system doesn’t have an automatic cut-off, the noise will go on for hours If a burglar walks in front of a motion sensor, the alarm will turn on Vibration sensors will respond if the window foil is broken Tamper sensors will trigger the alarm if a burglar tries to force the box open A magnet on the moving part trips a switch if the door is opened The alarm stops after a set time if it has an automatic cut-off devise Task 8: - Integrated circuit (1f) Circuit supply (2d) Alternating bias (3h) Primary cell (4b) Zener diode (5e) Remote control (6i) Reed switch (7c) Surface wave (8k) Vibration sensor (9a) Reverse current (10g) Main diagram (11j) Task 9: Sensing device Used to detect LDR Light Thermistor Heat Microphone Sound When light falls on the LDR, its resistance decreases 3 Using RV1 to adjust the sensitivity of the input Term Opposite Cut- off saturation Fixed resistor Variable resistor increases decreases energize De-energize Slow rapid To cause To prevent Forward bias Alternating bias The transistor in Fig protected from a large back EMF by a diode which is connected in reverse bias across the relay Task 10: The diagram shows a reed switch The reeds sealed in a glass envelope to protect them Because it helps to prevent corrosion of the contacts When a magnet is brought close to the reeds, they are magnetized, attract each other, and close When the magnet is removed, the reed open Task 11: The components are: switch, alarm bell or buzzer, battery, reed switch A 9V battery is connected to a set alarm switch and a set alarm switch is connected to an alarm bell An alarm bell is linked to a reed switch The circuit is open and nothing happens The alarm will ring Because when the magnetic insert in frame is brought close to the reed through open, the reeds create a closed circuit and operate the circuit