Arduino Motion Sensor

We will use a PIR motion sensor in this project. All objects (having temperature higher than absolute zero) emit radiations from the generated heat. These radiations cannot be detected by a human eye. Hence, electronic devices such as motion sensors, etc. are used for the detection of these radiations.

What is a PIR sensor?

The Passive Infra-Red sensors or PIR sensors detect motion or movement of an object that detect infrared radiations, such as the human body. Hence, the use of sensors is very common.

The advantages of using a PIR sensor are listed below:

Inexpensive
Adjustable module
Efficient
Small in size
Less power consumption
It can detect motion in the dark as well as light.

The PIR sensor is shown below:

The PIR sensor has three terminals, which are listed below:

VCC
Digital Output
GND (Ground)

We will connect the Vcc terminal of the sensor to the 5V on the Arduino board. The PIR's sensor output can be connected to any of the digital pins on the Arduino board.

The applications of the PIR sensor are automation, security systems, etc. Such sensors work great in detecting the entrance of a person in an area and leaving it.

The detection range of PIR sensors is from 5m to 12m.

Working of PIR Sensors

The working of the PIR sensor is entirely based on detecting the IR (Infra-Red) radiations, which are either emitted or reflected by the objects.

The infrared radiations are detected by the crystalline material present at the center of the sensor.

Consider a person passing in front of the background like a wall, etc. The temperature changes from room to body temperature and vice-versa within the sensor field. Changes arising in the arrival infrared radiations are converted by the sensor to the output voltage. It later detects the human body or object.

Structure of PIR Sensor

A round metal can is mounted on the center with the rectangular crystal that detects the IR radiations.

A ball like a lens present on some sensors helps in enhancing the viewing angle.

The bottom part of the sensor contains many circuits mounted on it, which is shown below:

Let's start with the project.

Hardware Required

The components required for the project are listed below:

1 x PIR motion sensor
Arduino UNO R3 board (We can take any Arduino board).
Jump wires
1 x red LED (we can take LED of any color)
1 x 220 Ohm resistor

Principle

The movement of jumper present on the sensor on the L side will cause a change in the state of the sensor whenever the motion is detected. Such a condition is defined as a single trigger mode.

When the sensor resets the timer after every detection of motion, it is defined as repeated trigger mode.

The two potentiometers present on the sensor are called as Sensitivity Potentiometer and Time Potentiometer. We can adjust both the parameters (time and sensitivity) accordingly.

It should be restricted for atleast 15 seconds in front of the PIR sensor for proper calibration in the output. After 15 seconds, the sensor can easily detect movements.

If any movement is detected, the LED will be HIGH. If there is no such movement, the output will be LOW.

Connection

The steps to set up the connection are listed below:

Connect the Vcc terminal of the PIR sensor to the 5V pin of the Arduino board.
Connect the Output terminal of the PIR sensor to pin 8 of the Arduino board.
Connect the GND terminal of the PIR sensor to the Ground pin of the Arduino board.
Connect the positive leg of the LED in series with 220 Ohm resistor to pin 13 of the Arduino board.
Connect the negative terminal of the LED to the Ground pin of the Arduino board.

Sketch

Consider the below code:

int LEDpin = 13;   // LED pin
int PIRpin = 8;    // The pin of Arduino connected to the PIR output
int PIRvalue = 0;  // It specifies the status of PIR sensor
void setup() {
 pinMode(LEDpin, OUTPUT);     
 pinMode(PIRpin, INPUT);
  // the output from the sensor is considered as input for Arduino
 Serial.begin(9600);
}
void loop()
{
 PIRvalue = digitalRead(PIRpin); 
 if (PIRvalue == HIGH) 
 {         
   digitalWrite(LEDpin, HIGH);  
   // turn ON LED if the motion is detected
   Serial.println("hello, I found you...heyyy..");
 } 
 else 
 {
   digitalWrite(LEDpin, LOW);
   // LED will turn OFF if we have no motion
   Serial.println("I cannot find you");
   delay(1000);
 }
} 