24GHz Human Motion Sensor Integration into HA - 2023

So you got one of those cheap 24GHz human motion sensor modules from ebay and you want to integrate it into your home security system. Should be easy as it has a "out" pin that goes high (3.3V) when a "human" (I find deers and even people in houses sometimes trigger this). I found expectedly that these modules do need to be treated with some care wrt RF interference. So I isolated it with a generic opto-isolater (I used FOD817A) as shown in the schematic below. By doing so it looks just like another old style magenetic door reed switch (closed when door closed. closed = no motion). To get the sense of the logic right I needed a 3.3V source redily available on the module as shown by small wired soldered to 3.3V on-board regulator.
So far my results are better than PIR or ultrasonic wrt the number of false detections but still inadequate as I get too many when no human is actually there. Wind through trees, humans in houses, and deer seem to set it off. I shall try reducing the sensitivity by putting the module behind layers of wood. So far a simple IR break beam detector works best.

(c) RHLamb 2023