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Re: Interesting Concept... or complete idiocy?
- To: ukha_d@xxxxxxx
- Subject: Re: Interesting Concept... or complete idiocy?
- From: Alan Shields <alan@xxxxxxx>
- Date: Wed, 20 Feb 2002 20:02:51 +0000
- Delivered-to: mailing list ukha_d@xxxxxxx
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take a look at
http://www.cix.co.uk/~pplunkett/x10.htm
Alan Shields
alan@xxxxxxx
On Wednesday, February 20, 2002, at 06:34 pm, Ian Lowe wrote:
I am fishing for the views of experts before comitting
time to something
that's obviouslly flawed.
As I understand it, X-10 signalling is basically this:
You place (and detect) a 1ms wide pulse of 120khz with an amplitude of
as
little as .1v 20ms or so after the zero crossing, such that after an
agreed
pre-amble, a burst means "1" and no burst means "0" this transmits
house
code, unit code, command a couple of times for redundancy.
Now, I saw some articles about improving X-10 range and reliability,
which
all centred around improving how accurately the reciever circuit was
tuned
to 120khz, and this got me thinking..
It started as "what if the 120khz oscillator was *very* precise?" I
figured
a PIC Chip with an XTAL clock could be that precise, and then I figured,
why
bother?
Why not just use the ADC in the PIC chip to analyse the powerline as an
analog signal, and watch for a burst of "noise" in the right place on
the
wave?
I figure if I used a large resistor to limit the current, and used some
circuit arrangement to "crop" the powerline "signal" so that I was only
looking at the segment from -10 to +10 I would be able to do some simple
DSP
on the line to watch for firstly, the zero cross, then a pulse of
"something
kinda like 120khz" in the right place.
As i recall, if you want to recognise (and replicate) a signal, your
sample
rate needs to be at least double the signal rate. so, for a 120khz
signal,
you would want to be sampling at 240khz. Given that even the fairly
basic
PIC12C jobs have a 10Mz clock, I'm sure sampling at 240khz wouldn't be
stressing things too much!
Just wondering if you could implement a basic X-10 module with very
little
in the way of components?
Does this seem deeply ridiculous? or just technically too bothersome?
or
might it even work?
Ian.
For more information: http://www.automatedhome.co..uk
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