Re: Signalling over power line

On Mon, 23 Jan 2006 23:24:25 -0800, avishay wrote:

> Thank you all, but the X-10 way is still way beyond the requirements. It
> is also too bulky for the space I have (it should fit inside an existing
> box) and too expensive.
> I thought of using a small current sense transformer, designed for the
> 20KHz-50KHz range, modulating the signal using FSK. On the receiving
> side, I want to put another transformer of that kind, bandpassing its
> received signal and detecting the FSK signal. Does anyone have an idea
> if such setup might work?

That is basically how X.10 works. It superimposes a high frequency signal
on the power line at 0, 60, and 120 degrees. They use 120kHz rather than
20-50kHz. Their coding strategy is to use a kind of manchester coding, in
which a binary 1 is encoded as a 120kHz blast at zero crossing (and at 60
and 120 degrees) followed by the absence of a pulse for the next 1/2
cycle. A 0 is encoded as no pulse followed by pulses. The pulses are
defined as 1ms of blast.

A communications protocol is built on top of this simple scheme using
various combinations of dead cycles, 0, and 1 bits. You'll have to come up
with your own scheme anyway, so why not use something that you know will
work? Also, if you implement the same scheme, you can use off the shelf
controllers if you want to extend the system.

--
Regards,
Bob Monsen

"I am turned into a sort of machine for observing facts and grinding
out conclusions."
-- Charles Darwin
.

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