Bobot

There aren’t a lot of examples out there for using Sparkfun’s  SEN-08630 PIR Motion Sensor. PIR stands for Passive Infra Red. The device comes with a 3 wire harness and is simple to use, albeit not entirely reliable. 

On a breadboard, connect the red and brown wires to V+ and V- on the Arduino. Place a 20k resistor between the signal wire (black) and V+. The Sensor uses open collector, so a pull up resistor is required. Connect the junction of the black alarm wire and resistor to Analog pin 0 on the Arduino. That’s it, it’s wired.

The Sensor requires a  3 -4 second reset/calibration period and if you don’t include it, once the alarm is triggered it will stay triggered until its power is removed.

Here is the Arduino sketch that I used with my circuit. While it isn’t immediate to react, it will and then settle down for the next reading.

// arduino sketch to control and process a PIR sensor.

//In this case it simply lights an LED to show triggering.
int alarmPin = 0;                 // asign  pins – alarm
int ledPin = 13;                    // and led pin

void setup () {
Serial.begin (9600);                         // setup serial

pinMode(ledPin, OUTPUT);           // Set LED pin as an Output
pinMode(alarmPin, INPUT);         // Set Alarm pin and an Input
}

void loop (){
int alarmValue = 0;                                           // zero the alarmPin
Serial.print(“IR = “);                                           // print the header
alarmValue = analogRead(alarmPin);        // read the sensor
Serial.println(alarmValue);                            // print the value
if (alarmValue < 100){                                     // check value output
digitalWrite(ledPin,HIGH);                            // yes? light up LED
delay(1000);                                                       // glow for a second
digitalWrite(ledPin,LOW);                             // shut off LED
}
delay(4000);                                                      // allow PIR to reset to environment
}                                                                               // loop back for next reading

This is a simple circuit, actually. But I was only able to locate a single incidence on the web –and it was wrong. Without the 4 second breather to allow the PIR to reset, their example once triggered would stay that way. My modification gives opportunity for a reset so the next reading would be accurate.

It is recommended that at least a pair of these sensors be used, in fact 3 provide the best results. All two or three may be connected to the same Arduino Analog input pin. Checking or agreement of the sensors will produce fairly accurate results.

Personally, I prefer using the Shape series of IR sensors.