Hardware Reference
In-Depth Information
X10 Interface
Module
TTL
Serial
Figure 9-10
An RFID-controlled home
(or office) automation system
using X10.
Synchronous Serial
(X10)
RFID
Reader
Microcontroller
X10
over AC
AC
power lines
X10 Lamp
Module
X10 Appliance
Module
X10 Appliance
Module
Lamp
Computer station
power strip
Computer station
power strip
What Is X10?
X10, a communications protocol that works over AC power
lines, is designed for use in home automation. Companies
such as Smarthome (
www.smarthome.com
) and X10.com
(
www.x10.com
) sell various devices that communicate over
power lines using X10: cameras, motion sensors, switch
control panels, and more. It's a slow and limited protocol,
but it has been popular with home automation enthusiasts
for years because the equipment is relatively inexpensive
and easy to obtain.
module is useful as a diagnostic tool because it already
works. When you can't get the appliance or lamp modules
to respond to your own projects, you can at least get them
to respond to the control panel module—that way, you
know whether the bits are passing over the power lines.
Smarthome sells versions of all four of these:
• Interface module: X10 One-Way Interface Module, part
number 1134B. You'll see two common versions of this:
the PL513 and the TW523. They both work essentially the
same way. The TW523 is a two-way module
—
it can send
and receive X10 signals
—
while the PL513 can only send.
X10 is basically a synchronous serial protocol, like I2C and
SPI. Instead of sending bits every time a master clock signal
changes, X10 devices send a bit every time the AC power
line crosses zero volts. This means that X10's maximum
data rate is 120 bits per second in the U.S., as the AC signal
crosses the zero point twice per cycle, and AC signals are
60Hz in the U.S. The protocol is tricky to program if you
have to do it yourself, but many microcontroller-develop-
ment systems include libraries to send X10 signals.
• Appliance control module: X10 Appliance Module 3-Pin,
part number 2002. These can control anything you can
plug into an AC socket, up to 15 Amps.
• Lamp control module: Powerhouse X10 Lamp Module,
part number 2000. These can control incandescent (not
fluorescent or neon) lamps only.
There are four devices that come in handy for developing
X10 projects: an interface module, an appliance control
module, a lamp control module, and a control panel module.
You'll be building your own controllers, but the control panel
• Control panel module: X10 Mini Controller, part
number 4030.
