How microwave movement sensors work.
Added 2019-05-03 04:45:02 +0000 UTCWhen I first came across these modules I was perplexed at their simplicity and use of a standard PIR (Passive Infrared Sensor) chip.
https://www.youtube.com/watch?v=Hf19hc9PtcE
It turns out that the design is very close to the old FM microtransmitter circuits, but with the inductor and capacitor components implemented as PCB tracks to give stable high frequency operation. It's very clever.
Comments
Thanks Clive, I learned something today.
Nuts 'n' Proud
2019-05-06 23:58:18 +0000 UTCYes. Optional resistors for reducing detection range and light sensor sensitivity if used, and an optional capacitor position for extending the time delay.
Big Clive
2019-05-05 17:43:40 +0000 UTCDid I miss the explanation of the pads on the back?
2019-05-05 16:00:27 +0000 UTC73s W1TOL
Witold Witkowski
2019-05-05 00:59:48 +0000 UTCHmmm. Bit esoteric for me. But interesting to see Clive battle through.
2019-05-04 12:00:49 +0000 UTCBadass. I love RF stuff. Studying for my general class ham license. Exam next Saturday!
Michael Thompson
2019-05-04 00:41:41 +0000 UTCI feel like I'm back in 3rd semester calculus class - lost, forever lost.
2019-05-03 22:58:51 +0000 UTCThe values will be so low they would require specialist equipment and techniques to measure. Even a short test lead would skew the reading.
Big Clive
2019-05-03 13:43:27 +0000 UTCAlien technology!! This is the first one where you nearly struggled to explain it! ;)
mikenco
2019-05-03 13:21:51 +0000 UTCWrong thread! :)
mikenco
2019-05-03 13:21:34 +0000 UTCHold on a sec - if you take the feed off the sense pin and fitted this little board to a stepper motor, assuming you could represent the sense voltage graphically using some code and it also knowing where the motor position is, this effectively could also be a mini RADAR?
Mark Wayt
2019-05-03 10:06:00 +0000 UTCNo peanut. Maybe Iβll get lucky
2019-05-03 07:04:17 +0000 UTCHi Clive, are you able to cut the traces, and isolate that capacitor system that is etched into the PCB and extract some sort of value of it?
Mike Wynne
2019-05-03 05:35:58 +0000 UTC
