>
> Richard:
>
> I did look at that circuit which is why I am posting for a simpler
> one. A lot of that circuit is for tripping a 12 volt relay which is
> irrelevant to interfacing to an MCU. And I do have that Futurelec
> motion sensor module -- it's a very nice unit, and reasonably priced,
> but it doesn't meet the requirements for my particular application.
>
I think you are going to need the circuitry right up to the final
transistor that triggers the relay. According to the device datasheet
(which could be better), the output is something like 3500 mV peak to
peak. To me, that implies an AC output of some kind.
Sure enough, the first thing the circuit does is strip off the high
frequencies with a low pass filter. Then it runs into that op amp
circuit and I'm not sure what it does but it looks like an
integrator/peak detector. The output is still AC although at a low
frequency (10 ufd capacitor coupling to the next stage) which, I
think, is an integrator. Finally, we get to the dual comparators that
determine that the final signal has exceed some threshold (high or
low) and one or the other drives the output transistor.
I don't think you are going to get a circuit that is much simpler.
You need everything right up to that transistor.
Then again, analog circuits aren't my thing. I could be way off but I
doubt it. In the end, they have done just what you would expect of a
black box: take the input signal, beat on it until it does what is
required and, finally, drive an output. If it could be simpler, they
would have done it.
Look at all the parts on the PIR Sensor Module! They wouldn't be
there if they weren't required!
Richard
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