PIR false trigger

Other Hardware Sensors
1

My concept is to use a Parallax PIR sensor to trigger an Arduino 328 Pro Mini 5V. It seems to work fine other than the false triggering which sometimes can be once a minute or so.

The code is written so that there is a minute of warm up time for the PIR sensor that occurs in the setup. The led then triggers whenever the PIR is high, but the squirt gun can only trigger after ten seconds has elapsed since the last time it triggered and the PIR is high. Could it be electronic noise that triggers the PIR?

In order to stop the false triggers, would it be worth trying any of these?

  1. Pull down resistor on the PIR pin?
  2. Low pass filter?
  3. decoupling on the PIR pin?

I thought I would get an opinion before I tore it apart

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2

It's a very simple circuit, and I wouldn't expect much noise, unless, say the line from the PIOR to the processor is quite long. A good first attempt would be a pulldown resistor on the pirPin.

Reorpt back when you solve the problem, as that may help someone else.

Good luck,

John Doner

3

I forgot to ask: do you have the PIR ground tied to the Arduino ground? Strange things happen to signals with floating grounds.

John Doner

4

If using outdoors, there are lots of things that will false trigger it. The sun, temperature changes, rain, snow, birds, trees, reflections, anything that moves.