X10 module frequency response

Several months back Dan Lanciani posted about a mystery signal in the 200kHz neighborhood that was blocking X-10 operation but that did not show up on an ESM1 meter.

I finally got around to running some tests. I used the PWM output of a PIC12F683 running at 8MHz (internal oscillator) measuring the frequency using my Digital Sampling Oscilloscope card. The signal level on the powerline was about 300mV. The signal waveshape was a little more triangular than sinusoidal.

LM14A and LM465 lamp modules were set to the same address and plugged into the same powerstrip (where the signal was injected). My pre-ELK ESM1 was also plugged into this powerstrip.

The PWM signal was continuous and I tested by sending ON/OFF commands via an RR501. The results are below. A YES means the module still worked (i.e. the injected continuous signal did not block operation) while a NO means the module operation was blocked. The ESM1 indicated a signal (one bar which would be ~2 bars on an ELK made ESM1) between 69.9kHz and 168.7kHz.

I would expect an X-10 made switch would perform similar to the LM465 but I have no switches so could not verify this. The LM14A performed much better than the LM465. I have no idea how switches and modules from other manufacturers would perform. FREQ (kHz) LM14A LM465

225.1 YES YES 202.7 YES NO 184.4 YES NO 168.7 NO NO ESM1

----- -- -- ----

101.4 NO NO ESM1 96.5 NO NO ESM1 92.5 NO NO ESM1 88.1 YES NO ESM1 84.5 YES NO ESM1 81.1 YES NO ESM1 77.9 YES NO ESM1 75.0 YES NO ESM1 72.4 YES NO ESM1 69.9 YES YES ESM1 I ran the series of tests twice and they repeated. A higher signal level might block over a wider range.

Shortly after posting the test data last evening I realized that I was using the wrong RR501. Instead of an older one that does not have collision avoidance and auto repeat I was using a newer one so I was really testing the RR501 rather than the LM14A.

I reran all the tests using the pushbuttons on an IR543 to be sure I was sending PLC signals at the time I intended. I used the relay in the RR501 to signal its response to the PLC signals.

Here's the new data. (The REG column is the PIC PR2 register value.)

X-10 Frequency Response (~=300mVpp)

-------------------------------------- FREQ REG LM14A LM465 RR501 ESM1

225.1 8 YES YES YES 0 202.7 9 YES NO YES 0 184.4 10 YES NO YES 1-SPORADIC 168.7 11 YES NO NO 1 155.9 12 YES NO NO 1 144.7 13 YES NO NO 1 135.1 14 YES NO NO 4 126.6 15 YES NO NO 2 119.3 16 YES NO NO 1 112.7 17 YES NO NO 1 106.6 18 YES NO NO 0 101.4 19 YES NO NO 0 96.5 20 YES NO NO 0 92.5 21 YES NO NO 0 88.1 22 YES NO YES 0 84.5 23 YES NO YES 1 81.1 24 YES NO YES 1 77.9 25 YES NO YES 1 75.0 26 YES NO YES 1 72.4 27 YES NO YES 1 69.9 28 YES YES YES 1

It turns out that the LM14A is unphased by the continuous ~300mVpp signal. Its Automatic Threshold Control (AGC is really a misnomer) is more impressive than I thought.