Sensors
HC-SR501 PIR module
Detect changes in infrared radiation caused by movement across a scene.
What it does
The lens divides the view into zones. A moving warm object changes the signal between zones; a stationary person can stop triggering it.
Connections and compatibility
Common modules accept 5 V power and produce a roughly 3.3 V digital output. Verify your board’s markings, warm-up time, and retrigger jumper.
Choosing one
A standard module with adjustable delay and sensitivity is enough. Small enclosures must leave the lens exposed.
Common mistakes
PIR is motion detection, not a reliable occupancy count. Sunlight, heating, pets, and position can change the result.
Use it in a tutorial
- Passive infrared (PIR) motion sensors — Read an HC-SR501 motion sensor and learn why movement detection is different from occupancy.