Apress - Smart Home Automation with Linux (2010)- P6 ppt

CHAPTER 1 ■ APPLIANCE CONTROL 8 This will support any incandescent lamp between 60 and 300 watts and can be switched on and off or dimmed by any X10 controller set to the same house code. The LM12U has a sister device, the AM12U, which works in the same work. The primary difference is that the AM12U is intended for appliances and therefore ignores any “dim” messages. The LM12U will also respond to two special messages, “all lights on” and “all units off,” provided they are sent using a matching house code. This module, like many of the others featured here, is placed in series with the power line acting like a logical AND gate. That is, both the lamp’s switch and the power switch at the wall must be on for the X10 “turn on” message to have any effect. ■ Note The code numbers given here are for the U.K. versions of these devices. Because of slightly—but significantly—different power systems used in various countries around the world, alternate modules are required according to your country. The LM12U in Italy, for example, is called the LM12I. Bayonet Lamp Module (LM15EB) This is also a simple zero-installation device but one that requires slightly more configuration. To install it, you plug it into an existing light socket and then reinsert the bulb (up to 150W) into its free end. Neither fluorescent lamps nor low-energy lamps should be used, though. The address is set by turning the lamp off and on again and then pressing the required house/unit code on the controller three times, once a second, within 30 seconds of it being switched back on. The light will come on once the code has been learned. There is also a screw-in version of the same device (LM15ES, with ES standing for Edison screw), although it is the bayonet version that’s shown in Figure 1-2. Figure 1-2. The LM15EB, 45 × 45 × 95mm CHAPTER 1 ■ APPLIANCE CONTROL 9 LM15EBs lack the dimming facility of the larger LM12U, but because they extend only 62mm farther than a traditional fitting, they are small enough to hide inside most lamp shades, making them SWMBO- friendly. 3 Again, the module acts like an AND gate, allowing the light to shine only when both the X10 command for “on” has been sent and the light switch would normally be on. Wall Switch (LW10U) As you can see from Figure 1-3, these are complete replacements for a standard light switch, which means you are limited in styling to white plastic. However, they are easy to fit into existing recessed switch boxes with only 16mm protruding from the wall. The unit’s address is set from a pair of dials placed behind the rocker switch and can be accessed by gently prying it off with a screwdriver. Care should be taken, however, because the plastic lugs that hold the switch onto the case are quite flimsy and would only suffer three or four removals before breaking. In addition to being controlled remotely by “on,” “off,” “dim,” and “bright” commands, the same functionality is available locally through the switch. Touching it once switches the light to full on or off, whereas keeping it held down will dim the light (if it is bright) or brighten it (if it is dim). Alas, the last brightness is not kept when you switch it off and then on again, nor can you slightly increase the brightness of a dim light without first making it fully dark, but local control means the light comes on immediately after pressing the button so as to not confuse any guests. Figure 1-3. The LW10U, 85 × 85 × 30mm This device also responds to the “all lights on” and “all units off” messages for matching house codes. 3 Most home automation enthusiasts are male, which has led to the acronym “SWMBO-friendly” being applied to any piece of technology that is attractive, small, hidden, discrete, or invisible to a normal occupant of the house. SWMBO stems from the British television series Rumpole of the Bailey phrase “She who must be obeyed.” CHAPTER 1 ■ APPLIANCE CONTROL 10 MicroModule with Dimmer (LWM1) This module is a turbocharged version of the LM10U and is shown in Figure 1-4. It works in the same way as the LM10U but is small enough to fit inside the wall outlet, allowing you to use any switch fascia you prefer. Figure 1-4. The LWM1, 40 × 40 × 15mm It supports all the existing functionality of the LM10U but can also remember the last brightness setting, allowing the light to be smoothly changed when it’s first switched on, which helps increases the bulb life. ■ Note The cheaper modules switch on at full brightness, so if you enjoy mood lighting, then this is a variant worth considering. Furthermore, this is one of the few devices in this section that supports two-way X10 communication. This means you can send a message to the device asking for its current brightness state, and it is able to reply. This is unavailable with most other devices, meaning you (or more specifically, your controller device) must remember the last message it sent, hoping it arrived, in order to emulate the querying of the lamp’s state. And even this result might be flawed if the brightness was changed locally. In most cases, however, this functionality is unnecessary because you rarely want to know whether the light is on. If you’re going to bed, then you’re not interested is whether the light is on or not, only whether you can switch it off. Unless you have a very large house, you can usually see a single light on in an otherwise pitch-black house and therefore know whether you need to resend the “all units off” message. The downside of this device is that it costs around three times that of the LM10U. However, there is a midrange product in the LW12 that features the same specification but without two-way communication. CHAPTER 1 ■ APPLIANCE CONTROL 11 DIN Rail Dimmer (LD11) This is a (very) high-power module, capable of controlling devices up to 700W, and it is consequently suitable for mains halogen as well as traditional mains lighting. Instead of being used in place of a switch (like the LWM11) or in connection with the bulb (like the LM15EB), this device is remotely placed near the fuse box, with the LD11 output cables running into the light directly. This is a switch terminal on the LD11 that allows the appliance to be switched on and off, as if it were local. However, with four (potentially) long cable runs from the appliance to the LD11 (two for power and two for control, as visible in Figure 1-5), its purpose isn’t so obvious. Figure 1-5. The LD11, 50 × 80 × 70mm The primarily purpose for the LD11 is mood lighting, thanks to its support for halogens, and scene lighting, thanks to its soft dimming and memory functions. Because they are generally placed away from the devices themselves, you get a much cleaner install. The cost in cabling is thankfully offset by the cheaper cost of the module. If you use the LD11 to power lighting sockets, they must be used only by lamps, since the dim feature will destroy many other types of appliance. To aid in this, you can use nonconventional plugs and sockets for the lamps and LD11-fed outlets. If your country uses square pin plugs, source some rounded pins, and vice versa. Appliance MicroModule (AWM2) This module uses the A prefix because it is primarily intended to control appliances; however, its function is also suited to lights. The AWM2, shown in Figure 1-6, sits inside a standard wall outlet and supports two switches. One switch controls the locally connected lightbulb (and sends an equivalent X10 message onto the power line), while the other switch sends an X10 “on” or “off” messages to the next address in sequence. So, if your AWM2 is configured to E2, you can also control E3 from the same switch. By installing two identically configured units at the top and bottom of the stairs, you can control both the upstairs and downstairs lights from either location with no rewiring. And since this is an internal module, you can use any switch facing your choose. Note, however, that this device doesn’t support dimming. CHAPTER 1 ■ APPLIANCE CONTROL 12 Figure 1-6. The AWM2, 46 × 46 × 18mm Controlling Appliances For appliances that are supplied without X10, such as teakettles, toasters, and HiFi units, a second type of device is needed. These function in much the same way as the LM12U or LM15EB/LM15ES, whereby the device is plugged into an existing power socket and the appliance in question is plugged into the X10 module. As mentioned previously, these require the switch on the wall socket to remain permanently on, along with any switch on the appliance itself. This further implies that any device plugged into such a module that could be controlled remotely must be safe at all times. In the case of the teakettles, for example, it must contain enough water so it won’t boil dry. Appliance Module (AM12U) Like its sister module, the LM12U, this is a very simple “plug in and go” device that, although it looks the same (see Figure 1-7), has three very important differences: • It has no dimmer support. • It can control fluorescent lights. • It can operate at much higher loads (up to 500W for incandescent lamps, 1A for inductive 4 appliances like fans, and 16A for resistive loads 5 such as heaters). Consequently, its intended purpose is to automate units such as fans and teakettles. However, high- power devices such as vacuum cleaners and fan heaters rarely work on these modules because of the back-EMF created by the collapsing magnetic field around the motor when it is switched on or off. This 4 Inductive loads use magnetic fields and are usually characterized by motors or solenoids. 5 Resistive loads convert electrical current into other forms of energy, such as heat. . There is also a screw-in version of the same device (LM15ES, with ES standing for Edison screw), although it is the bayonet version that’s shown in Figure 1-2 . Figure 1-2 . The LM15EB, 45 . units off” messages for matching house codes. 3 Most home automation enthusiasts are male, which has led to the acronym “SWMBO-friendly” being applied to any piece of technology that is. that features the same specification but without two-way communication. CHAPTER 1 ■ APPLIANCE CONTROL 11 DIN Rail Dimmer (LD11) This is a (very) high-power module, capable of controlling