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 3.3 V 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 our PIR sensor tutorial page!

The BS412 sensor window is 4 mm x 3 mm and has a smaller sensing element whereas BL412 sensor window is 5mm x 3.8mm and has a larger sensing element (so it will be more sensitive).

Note: PIR sensors and the Raspberry Pi sometimes don't get along - if you're having false trigger reports, make sure the PIR Sensor is far away from the Pi