The PIR sensors (HC-SR501) are often referred to as, "Passive Infrared" or "IR motion" sensors, which enable you to sense motion. Everything emits a small amount of infrared radiation (IR), and the hotter something is, the more radiation it emits. PIR sensors are able to detect a change in average IR levels of their detection zone (e.g. when a human enters a room, that room will increase in temperature slightly) and hence senses motion.
This unit can be powered via the
Raspberry Pi's 5V output, and be read directly from the Raspberry Pi's
GPIO input (as the sensor has a digital 3.3V output!).
This PIR includes an adjustable delay before firing (approx 0.5 - 200 seconds), has adjustable sensitivity, and two M2 mounting holes! It runs on 4.5V-20V power (or 3V by bypassing the regulator with a bit of soldering) and has a digital signal output (3.3V) high, 0V low. Its sensing range is up to 7 meters in a 100-degree cone.
Input Voltage: 4.5V - 20V
Current Draw: <50µA
Digital Output: 3.3V (High)
Digital Output: 0V (Low)
Working Temperature: -15°C to 70°C
Delay Time: 0.5 - 200 Seconds
Sensing Angle: 100° Cone
Range 5m - 7m
Sensor Lens Diameter: 23mm
Height (with lens): 24.66mm
Centre screw hole distance: 28mm
Screw hole diameter: 2mm (M2)