Mini Basic PIR Sensor - BS412

via Adafruit
$3.90
SKU AF-4666

PIR sensors are used to detect motion from pets/humanoids from about 5 meters away (possibly works on zombies, not guaranteed). This sensor is much smaller than most PIR modules, which makes it great for unobtrusive projects. It's also fully-contained - only needs power, ground and a resistor to set the delay time - and breadboard or perfboard friendly.

Runs on 3.3V power - so make sure if you're interfacing with an Arduino or other 5V chip, you power it from the 3V regulator. Digital signal output is 3.3V high/low and you can change the length of time the signal pin stays high by connecting a resistor divider to the second pin, from 2 seconds (0V) up to one hour (3.3V) - see the datasheet 'on time' table for recommended resistor values.

To use, see datasheet page 7 pin-out diagram:

  • Connect pin #1 to ground
  • Connect pin #2 to ground (on time of 2 seconds)
  • Connect pin #3 to 3.3V
  • Check signal on pin #4

The snap-on lens is focused to 5 meters away with a 120 degree spread, but should work from about 3 to 8 meters. These are smaller and less expensive than our PIR modules, and you'll find the performance is OK but not as great as the larger modules, for example not having as wide of a range and taking longer to trigger.

For a PIR tutorial with CircuitPython and Arduino code examples and project ideas, check out Adafruit's PIR sensor tutorial page!

The BS sensor window is 4mm x 3mm. We also carry the BL412 PIR sensor which has a larger sensing element (so it will be more sensitive).