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Re: Sensor systems Oil watchman, technical details wanted |
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| message from Andrew Gabriel on 9 May 2004 |
I played that game with the Oregon Scientific remote thermometers.
Actually, a trawl around the web revealed someone had analysed the
protocol for that, not fully but well enough. A scope on the output
of the receiver in the Oregon Scientific showed a nice square wave
digital signal appears when one of the transmitters sends data.
However, a scope on the output of the 433MHz receiver I bought (CPC)
just spewed garbage -- the digital signal appeared during reception
but I didn't fancy trying to separate it from the noise. If I was
going to persue this, I would probably by another Oregon Scientific
receiver just to steal the 433MHz receiver out of it. In the event,
I decided to do it all a different way (which is more accurate, more
reliable, and cheaper than using the Oregon Scientific units).
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| G&M replied to Andrew Gabriel on 9 May 2004 |
The noise will possibly be the coding - could be RTZ (return to zero), NRZ,
(non return to zero), Manchester encoding or a few others, plus then the
data will possibly need to go through a UART to translate the HDLC protocol.
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| Dave Liquorice replied to G&M on 10 May 2004 |
There isn't a continuos carrier with these systems, many Tx/Rx pairs
share a common frequency. Each Tx only transmits for a short period
(<1s). So the noise probably was noise from an unsquelched receiver.
The fact that the data stream showed clearly, when present, says that
to me.
A simple squelch can be made from a HPF and detecting what passes the
filter, lots of stuff = noise, not much = signal.
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Archived message: Re: Sensor systems Oil watchman, technical details wanted (UK DIY House Renovation)
