Re: CM11A hangup: Any better products?

[Joerg <notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx>]

Hello Dave,

>>What I found with X-10 modules a lot was that their resonant circuit was
>>quite far out of tune. That made a huge difference in some. The
>>receivers were ok (not great) but they were listening on the wrong
>>frequency until adjustment. Since it's an AM protocol a strong signal
>>will still get through.
>
> I'm curious how you determined that the modules were mistuned.

I became suspicious when I found that a module didn't work reliably in
an outlet and another module of the same brand (they actually came with
the same shipment) worked every single time in the same outlet. So, I
got a schematic from the web and opened both.

CAREFUL: You have to be extremely careful and know what you are doing
since the circuitry in there is on live mains voltage, including the
signal processing part. Do not touch anything while the module is
plugged in. I used a power strip to avoid having to directly plug in and
out disassembled modules.

Even though the US modules are polarity keyed all it takes is a miswired
outlet and there can be the full mains voltage on what you thought
should be ground in the module. In Europe it is worse in some countries
because many of their mains plugs and outlets are not polarity keyed.

Then I made myself a Hi-Z toroid pickup circuit for the oscilloscope
which I could solder on while the module was unplugged. This would also
protect the oscilloscope. I looked at the amplitudes on the other side
of the tuned circuit while sending lots of bogus codes with a wireless
remote via the transceiver. The flakey module showed only half the
amplitude of a "good" module. That was a whopping 6dB less sensitivity
which is a lot for X-10. It was simply listening on the wrong frequency.
Now I took a good communications receiver and verified the frequency of
the transceiver, to make sure I wouldn't adjust all the modules to the
wrong baseline frequency. It was pretty much right on.

After tuning them all with a fully isolated alignment driver (from a
Bernstein kit) they all performed fine. There was no longer a difference
in reliability between modules on this "far away" outlet. I did not do
the in-wall dimmer modules because they worked ok and I didn't want to
go through the hassle of taking them all out again.

> I've looked at the frequency of several X-10 transmitters and found all to
> be at 120kHz.

I found the transceiver and the CM11A to be pretty close to 120kHz but
not all of the receivers.

Again, for anyone reading here: This is just a recollection of what I
did, NOT ADVICE. Tampering with the modules can be dangerous.

Regards, Joerg

http://www.analogconsultants.com