Passive Infrared sensors

 

PIR is a device  which can detect sensor and infrared radiation that are emitted by any living beings(humans and animals), also due to this PIR are mostly used in house as a security.

Hardware required :

Arduino Uno

Jumper Wires

LED

HC-SR501 Passive Infrared Sensor

This PIR sensor consist of 3 pins (VCC, Ground pin , and Output pin in the middel)

Here we will connect VCC of PIR to Arduino 5 volts. Likewise connect ground to ground pin and connect output pin of PIR to digital pin no.3 of Arduino. Lastly place LED positive leg  to  pin 13 and negative leg to  GND of Arduino.

Code

/the time we give the sensor to calibrate (10-60 secs according to the datasheet) int calibrationTime = 30; //the time when the sensor outputs a low impulse long unsigned int lowIn; //the amount of milliseconds the sensor has to be low //before we assume all motion has stopped long unsigned int pause = 5000; boolean lockLow = true; boolean takeLowTime; int pirPin = 3; //the digital pin connected to the PIR sensor's output int ledPin = 13; ///////////////////////////// //SETUP void setup(){ Serial.begin(9600); pinMode(pirPin, INPUT); pinMode(ledPin, OUTPUT); digitalWrite(pirPin, LOW); //give the sensor some time to calibrate Serial.print("calibrating sensor "); for(int i = 0; i < calibrationTime; i++){ Serial.print("."); delay(1000); } Serial.println(" done"); Serial.println("SENSOR ACTIVE"); delay(50); } //////////////////////////// //LOOP void loop(){ if(digitalRead(pirPin) == HIGH){ digitalWrite(ledPin, HIGH); //the led visualizes the sensors output pin state if(lockLow){ //makes sure we wait for a transition to LOW before any further output is made: lockLow = false; Serial.println("---"); Serial.print("motion detected at "); Serial.print(millis()/1000); Serial.println(" sec"); delay(50); } takeLowTime = true; } if(digitalRead(pirPin) == LOW){ digitalWrite(ledPin, LOW); //the led visualizes the sensors output pin state if(takeLowTime){ lowIn = millis(); //save the time of the transition from high to LOW takeLowTime = false; //make sure this is only done at the start of a LOW phase } //if the sensor is low for more than the given pause, //we assume that no more motion is going to happen if(!lockLow && millis() - lowIn > pause){ //makes sure this block of code is only executed again after //a new motion sequence has been detected lockLow = true; Serial.print("motion ended at "); //output Serial.print((millis() - pause)/1000); Serial.println(" sec"); delay(50); } } }

Outcome

As from the video we can see that the LED light lights up whenever any things pass near by the PIR Sensor