Datasheet

Jon Waddington
22
3.4 Home Automation
The first item, “Home Automation”, allows the user to directly control the X10 devices. A
full list of devices in the Propeller’s memory can be listed or, if required, the devices can
be listed by the room which they are in. Once a device is selected, the user can select
whether they wish to turn the device on or off. In the case of a lamp module, there is an
option to dim the light. The user is then prompted to enter a value between 0 and 100 to
dim the light, 0 turns the light off and 100 leaves the light on at its original brightness.
3.4.1 X10
X10 is an industry standard method of communicating with electrical appliances around
a building over the mains power line. The data consists of bursts of radio frequency
signals to represent digital data. This method of transmitting and receiving data mean s
that no additional wiring is required to install X10 devices when implementing home
automation [28].
The data is sent from the X10 controller to the modules during the 200ms time period
following a 0v transition of the AC mains power signal, as this is the point where less
noise is likely to be present in the signal. The burst of data is a 120kHz signal which lasts
for approximately 1ms. The data is sent another 2 times to coincide with the 0v
transitions of the other phases in three-phase systems. This ensures the X-10 device can
be used in industrial and commercial buildings where the three-phase system is used
[29].
The information transmitted through the power-line can be separated into 3 sections.
There is a 4 bit start code, which initiates the communication, there is a 4 bit house
code, which is generally the address shared by all the devices in the building, and there
is a 5 bit data code which may represent the address of the particular device or the
required function for a device to perform.
The start code is always ‘1110’. This code is transmitted over the zero crossing points
over 2 cycles of the AC mains signal.