Appliance Control: Making Things Do Stuff - Smart Home Automation with Linux and Raspberry Pi - page 6

Device Modules
I'll now cover the multitude of devices available on the market that can be controlled by X10, in other words, those
that contain a receiver. These break down into three categories:
Internal : Where the X10 receiver and the thing it controls are within the same physical form
factor. An example is motorized curtain rails.
Local control : The X10 receiver processes the message but controls the power to something
directly wired into it. An example is light switches.
Plug-in modules : These fit into a standard power socket, and an external device is plugged
into them. The X10 logic determines whether to allow the flow of current between them.
An example is appliance units.
Controlling Lights
This is by far the most common type of device, and accordingly there are several different devices to choose from,
all known in X10 parlance as lamp modules . However, it should be noted that some lights cannot be attached to lamp
modules at all. These include the fluorescent lighting strips found in most kitchens and their compact fluorescent
lamp equivalents (often known as energy-saving bulbs ) now making their appearances in homes around the country.
To make matters worse, these bulbs can also introduce spikes on the power line that can turn off nearby X10 lights. 2
The primary functional difference between the various lamp modules is whether the device in question supports
dimming. When a light is dimmed, the alternating voltage is not reduced in amplitude. Instead, small portions of the
power sine wave are removed, which effectively turns off the lamp for short periods of time. Consequently, the bulbs
filament is charged and discharged many more times a second than usual, which creates a changing electromagnetic
field. This can result in the filament starting to vibrate and creating an audible hum. This is not usually a problem with
light bulbs (and you can always buy rough service bulbs that hold the filament steadier to prevent this movement), but
it is dangerous to other appliances that are not built for it.
Note that many countries are phasing out the old incandescent light bulbs due to their relative inefficiencies,
compared with newer alternatives, such as LED, compact fluorescent lamps, and halogen.
Lamp Module (LM12U)
This is a simple affair that requires zero installation. You simply plug it into a free wall socket, set the address using the
dials on the front, and plug your lamp into the socket on the front, as shown in Figure 1-1 .
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