Pyroelectric.md

Pyroelectric Motion Sensor

• KEYWORDS: Pyroelectric Motion Sensor,PIR,Motion,Movement,Sensor,HC-SR501

Pyroelectric (PIR) Motion Sensor's are what you'd find in a home burglar alarm or a motion sensitive light. The module shown is the HC-SR501, and it outputs a 3.3v pulse on the output pin whenever movement is detected (some units may be open drain, or output a pulse at the operating voltage). The length of this pulse is adjustable by one of the potentiometers on the unit, being about 2 seconds long at the minimum setting, and 5 minutes or more at the maximum setting (allowing it to control motion sensing lights without external components).

The HC-SR501 draws less than 50uA when it is on, which means it'll run off a battery for ages.

Connect as follows:

HC-SR501	Espruino
VCC	VBAT (5v)
OUT	A1
GND	GND

Note: any GPIO pin will do for OUT

You can then easily trigger something to happen when movement is detected:

setWatch(function() {
  console.log("Movement detected");
}, A1, {repeat:true, edge:"rising"});

Specs

Specification	Value
Input Voltage	4.5-20v
Output Voltage	0 (low), 3.3v (high)
Current Draw	< 50uA

Using

• APPEND_USES: Pyroelectric

Buying

• eBay