In April 1995, I started
receiving X-10 commands from my neighbor down
the street. I decided to install a device to address this.
to this, I only had a 1uF capacitor bridging the phases installed in a
plug located at the outlet of my clothes dryer.
The device's principle
of operation is quite clever. In a conventional
design, you would have to insert an inductor of sufficient value and
rating in series with each incoming power phase. The size of such a
can be enormous. Instead of that approach, the ACT blocker is a
transformer. The installer passes the neutral conductor to the house's
breaker panel thru a hole in the noise blocker and connects the
neutral and power phase connections to screw terminals on the device.
that the device is not in series with the house, thus mega size
are not needed. The actual operation of the circuit is not 100% clear
me, but it functions roughly as follows: when an offensive signal is
by the module, it somehow figures out its source (either from in or
the house), and then magnetically induces a voltage of the proper
on the segment of the neutral cable that is inside the toroid's hole.
effect is that the signal will be cancelled out. For example, if there
appears 10mV of signal on phase A, it will be automatically be coupled
also to phase B. ACT's blocker then induces roughly 10mV of signal onto
the neutral, and the effect is that the house 'sees' no signal, since
exist an equeal amount of 'noise' on all three connections.
The X-10 repeater from
ACT. It is installed into the wall of
my utility room
Each X-10 transmission consists of two
identical halves. The CR230 repeater works by decoding the
half, and then sending out a copy of it which occurs concurrently with
the second half of the transmission. As a result, the signal
strength of the second half is much higher than the first.
can clearly be seen by my ESM1 X-10
. I see a short bar blip on the display
(from the original sender) followed by a long bar (amplified by the
CR230). This is a very distinct signature as all previously
signals produce two bars of the same length. It is not known
the CR230 phase locks onto the 120 KHz signal by the original sender,
but if I were to design this box, I would certainly have done
that. This would ensure that the signals of the CR230 and the
original transmitter are in phase, and would not interfere
In my research of the device, I tried to find out if all X-10 receivers
would work with just one copy (half) of the full X-10
This is because regions in the home that have weak signal would only
'see' one half of the command (the half that was amplified by the
CR230). The general consensus on the newsgroups is that
would work with all devices. Also, Phil
advised not using both the CR230 and the CP303
in the same installation. I have
not found this to be a problem.
In actual testing I have found seamless behavior, and communication
over the whole house has improved. There are two particular
breakers/zones that are problematic, and initial testing shows this has
improved considerably. Further use will show if this is a
permanent solution (see Project log below).
Board inside the CR230. Note charred area at the bottom
(Image from 2020)
X-10 Signal Booster
One day in November 2008, I found
that many of the X-10 signals in the home were not making it
through. The problems were not related to jumping across the
phases, but could extend to same phase. After lots of looking
with my ESM-1 signal strength meter, I found that the two 5V switching
supplies for my Vonage boxes were the signal disrupters. I
isolated them with an inductor, but this event caused me to decide to
look for any high power X-10 Boosters that were available. I
found the XTB
(X10 Transmit Booster)
, developed by Jeff Volp after some
I purchased a unit, and the parts kit is pictured below. His
attention to detail is very impressive. The kit is complete
to the professionally printed decals, and the light tube for the LED.
Photo of complete kit to assemble an XTB-IIR.
Assembly took about 2-3
Saturday afternoon, and the unit worked immediately. It takes
fair amount of experience to assemble this kit as the component values
on the capacitors need to be carefully read. I must reiterate
impressed I am with this kit. The case was custom machined to
the various parts. A very well designed system
Photo of assembled
unit. It fits neatly into
The XTB-IIR has two
operation. In the first, an X-10 transmitter (such as the
can be plugged into the outlet on its front cover, and any of its
transmissions are boosted to ~20Vpp levels (at the unit).
Incoming signals are also amplified. This is an impressive
clever feature. In addition, the unit also has TW-523
and has an RJ11 jack for that purpose. Snapping in the
from my home automation system, I now have a high-power transmitter for
The XTB-IIR is meant to be installed where both phases of the power
line are available. However, this is not convenient for me,
used it only in single phase mode. I have both a passive
(capacitor) and the ACT CR230
on my breaker panel.
Before installing the
signal amplitude of the transmissions from my home controller varied
from 1Vpp (basement) to 0.1Vpp (upper floor, loft). It seems
the amplitude is greatly affected by the distance to the main breaker
panel. After the XTB-IIR was installed the amplitudes
appear to increase by a factor of 2 or 3. Thus the basement
amplitudes in the 2-3Vpp range, and the upper floor loft saw a signal
amplitude of about 0.3Vpp. This latter location has always
the lowest signal levels in my home, and it should have adequate signal
Disclaimer: I have no financial involvement with Jeff's
I purchased an XTB, and he gave me a complimentary upgrade to an
In 2011, I added several high-tech electronic loads (HDTV, BluRay
player, etc) and noticed another degradation in the X-10 performance.
Measurements show that they all had several uF of capacitance
the power line, probably to suppress emitted switching noise.
past, I have opened units like this and removed the capacitor on the
power line, but I decided to install a localized high frequency block
on these. I have a few dead X-10 wall switch modules, and
an inductor in them to block the X-10 signal from being shorted out by
the light bulb. I thought of the idea of installing these
the main power strip.
Inductor installed into the power strip.
The inductor has a measured value of 35uH, and they are wound
enameled 18 AWG wire. This is rated to 2.3
installed one in each power strip after the circuit breaker per the
photo above. The first application of one of these showed
elimation of the particular communication problem. I
one of these in each of the areas with lots of electronic appliances.
In subsequent years, I have successfully used a 500uH, 2 Amp
(part number M8274-ND
at Digikey). This has a diameter of 0.56" and a length of 1.25".
X-10 Line Signal Monitor
With all the time spent working from home in 2020 due to the COVID-19
virus, I decided to work on another microprocessor project. This
time I wanted to build a device to monitor the amount of high frequency
signal on the power line. I have had the ELK ESM1
for years, but it only gives a simple bar graph display.
I based the front end of the circuit on the one in a wall switch module
This circuit has capacitors to isolate both sides of the power line and
then uses a transformer to couple the high frequency portion over to the secondary ground.
Since I had a few dead wall switch modules, I could readily
salvage them for parts.
Initial prototype using a wall switch module.
As you can see from the schematic diagram
the signal from the coupling transformer is amplified by op-amp IC1.
This is a non-inverting amplifier with a bandpass in the 120kHz
region formed by L1 and C4. The output is then rectified and sent
to a simple RC filter for amplitude measurement. From tests with a
signal generator at the 120V plug, I measured a sensivity of 1.4mV per
A/D bit. Thus each count from the 16F877 PIC's A/D means 1.4 mV of
signal or noise on the power line.
are two ways to view the signal from the power line. For the most
direct way, I connect my mini-scope to the amplified and filtered
analog signal. The scope is then triggered by the zero crossing
signal from the TW523. This results in a very stable waveform and
allows you to directly view the power line contents during the first
msec after the zero cross.
The second way is to have the
PIC sample the power line. In this method, the A/D on the PIC is
used to average one msec worth of samples (about 60 samples) to provide
8 values representing 8 of the 8.3 msec of a half wave of the power
line. In the latest firmware, the serial interface refreshes
every two seconds the bottom line with this information. In
addition, this sampled information is used to show the strength of
individual X-10 commands, but sent and received.
Assembled X-10 monitor test
example output of the analog portion can be sampled at Test Point TPB.
This is shown on my mini-scope below. The zero cross occurs
one division from the left, and in this image the scope is sweeping at
1msec/div. Thus this shows the amount of noise/signal in one half
wave of the power line. The next zero cross occurs approximately
0.7 divisions in from the right as each half wave takes 8.3 msec.
PIC that samples this and the output of a TW523 is accessible via
serial line. This can be accessed on a PC by a serial terminal
such as Tera Term. Below is an example session:
the Power Up Banner is shown you can issue commands such as sending an
X-10 command over the power line. Once that is completed, it will
show the actual signal level that was achieved. In the example
above, there are 83 units of signal when a 0 was intended to be
transmitted and 188 when a 1 was sent. This difference of about
100 units means that the measured output signal was 140 mV. This
gives the user a sense of the impedance of the power line at the local
power outlet as the lower the impedance, the lower the achieved
measured output will be.
The line after the transmit shows the
result of a received command. The measured signal of each bit is
shown (not including the "1110" in the X-10 header). After the
numeric strength is displayed, a symbol is shown to indicate the
polarity of the digital output line of the TW523 for that particular
bit. The '-' is for a logic '1', and the '_' for a logic '0'.
You can see for example that the first bit (after the header) is
a '1' with a received strength of 164 units. The next bit should
be then a '0', and that conforms with the display above, showing it had
a line level of 94. The rest of the bits then follow, and finally
the command is decoded and shown after the '>' symbol. This is
an F-2 command. Lastly, it shows the highest level for the '0'
commands, and the lowest level for the '1' commands. The larger
the difference of these two levels, the larger the signal to noise
ratio. Note that in this case the data was taken in an area with
high noise levels. In a quieter location, the received amplitude
for '0' bits is less than 10 units.
Finally, on the bottom line
you see the Line Status, which is updated every two seconds. It
continously refreshes 8 numbers, each of which is the signal level for
a 1 msec time frame. This line thus gives snap shots of the
received signal for 8 msec, or most of one half wave. The first
sample needs to be small as this is when the X-10 signal is exchanged.
functions that can be seen in the Power Up Banner are 'b' for beacon
mode. This causes the Monitor to continously transmit a pulse at
the power line peak. This was meant to check for capacitors on
the power line without interfering with the X-10 signal exchange.
As of this writing, I have not used this feature very much, but
that may change in the coming months as I use this device.
built the unit to be portable but it looks like the best location for
this is at my breaker panel. I used a spare Cat 5 cable to
transfer the serial stream to my main home automation PC and can see
the serial stream from anywhere with VNC. So I can use the system
by walking around the house with a plug in transmitter. It
occurred to me after installation that I should have built in two
analog receivers, one for the A phase and one for the B. I will
just move it from one phase to another.
July 2020 Update. I added a Bluetooth terminal to this device to allow wireless interaction. See here