PIR + Electron = False alarms

This might be useful to others who are trying to figure out why their PIR is triggering when there is no motion.

After connecting a PIR of a type that I have used successfully on many ESP8266 projects, I needed a motion alert over cell data instead of wifi, so I wired it up to an Electron.

It worked great, except once an hour or so, I would get an alert with no actual motion.

After puzzling a while, I determined that it was the cell signal that was setting off the PIR sensor. When the Electron did its handshake, the PIR was set off. I am located quite far from cell towers, so the signal is probably transmitted at maximum power.

Some experimenting with my phone showed that it would trigger it up to half a meter away from the sensor.

Since this kind of bug can be hard to track down, especially if you are new to the device, I thought I would post this for others to be aware of.

Solutions would be RF hardened sensors, or at least making sure that the sensor is well away from the Electron antenna (and phones). Perhaps shielding and ferrites would also help with some sensors. It all depends on budget and how necessary zero false positives are.

Happy hacking to all.


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What’s your code?