Moteino with RFM69HW 915MHz false triggers HC-SR501 Motion Sensor [solved]

[Felix]

Did you try another PIR sensor?

[Marcus]

Hi Felix,

yes I tried another one, identical from the same batch I guess. They are those cheap, generic chinese PIR sensors, but I guess the chip, components and the layout are almost the same in all of them.

Tested the prototype of clap sensor and it seems to work ok when I ignore it's output following the radio transmit. It's really sensitive to voltage fluctuations though, but what to expect from op amp gain of 1000. But with lower gain the microphone output is not high enough to sense clap from across the room.   But then I bumped into another problem when trying to enter sleep mode: when Moteino is put to sleep there's a slight overshoot in 3.3v rail voltage (around 60-70mV), caused maybe by the sudden lower power consumption of 328p that the MCP1703 cannot  react fast enough. The blip lasts around 2ms but is slow enough to cause the biasing voltage to electret mic to fluctuate by a dozen mV or so. And with a gain of 1000 the voltage threshold is passed and sensor is triggered, which causes Moteino to awaken again, so it cannot really get any sleep

I have again tried so many combinations of capacitors everywhere to dampen that fluctuation but nothing seems to help. Next step would be to isolate the op amp board with a separate regulator, I guess.

[omatzyo]

I'm having the exact same problem with the following PIR:

https://www.adafruit.com/products/189

Happens every time the radio activates, even if they are completely on isolated circuits.  Moving away resolves.  Haven't figured out an effective way to shield the sensor yet.  Could any of you save me some time?  What were your ultimate solutions?

[Felix]

Try resuding the power of the radio by calling radio.setPowerLevel(N) with N=[0,31] (default is max of 31).

[joelucid]

Cross reference to a post that describes how I solved a similar issue:

https://lowpowerlab.com/forum/index.php/topic,1478.msg10313.html#msg10313