Embedded Sensor – Passive Infrared Sensor (PIR)

• PIR – Passive InfraRed Sensor
• PIR consists of a Pyroelectric sensor which generates energy when exposed to heat.
• The module covered with Fresnel Lense Cover.
• BISS0001 micro Power PIR Motion Detector IC.

---

Infrared Application

• Passive Infrared Detector for Anti Theft security alarm system.
• Passive Infrared Detector based Light On/OFF.
• Automatic Light  ON/OFF.
• Many other motion Detection Application.

---

Different PIR Modules

The HC-SR501 PIR Sensor Module

• Working voltage : 5v to 20V DC
• Range : 3 to 7 meters
• Induction Lens size: 23mm.
• PCB Size: 32mm x24mm.
• Pins Details
  • Ground pin
  • VCC pin
  • The output pin detects an object when it is at a high logic level.
• Two potentiometers.
  • One for adjusting the sensitivity of the sensor
  • Adjust the time for the output signal to stay high when an object is detected from 0.3 seconds up to 5 minutes.
• Jumper Settings (Selecting the trigger modes)
  • non-repeatable trigger – when the sensor output is high and the delay time is over, the output will automatically change from high to low level.
  • Repeatable trigger –  will keep the output high all the time until the detected object is present in sensor’s range

---

Arduino Example code :

Circuit

Code

/* Arduino PIR Motion Sensor Tutorial */
/* www.ArunEworld.com */

int pirSensor = 8;
int relayInput = 7;

void setup() {
  pinMode(pirSensor, INPUT);
  pinMode(relayInput, OUTPUT);
}

void loop() {
  int sensorValue = digitalRead(pirSensor);
  if (sensorValue == HIGH) {
    digitalWrite(relayInput, LOW); // The Relay Input works Inversely
  }
}

---

Code Explanation

This Arduino code is for a PIR (Passive Infrared) motion sensor setup, where a relay is controlled based on motion detection. Here’s an explanation of each part:

Section	Explanation
Comments	The code includes comments providing information about the purpose of the code and its source.
Variable Declaration	– pirSensor = 8;: Declares a variable pirSensor and assigns pin 8 to it for reading the PIR sensor’s output. – relayInput = 7;: Declares a variable relayInput and assigns pin 7 to it for controlling the relay.
Setup Function	Initializes the pins: – Sets pirSensor pin as INPUT to receive data from the PIR sensor. – Sets relayInput pin as OUTPUT to control the relay.
Loop Function	– Reads the digital state from the pirSensor pin to check for motion detection. – If motion is detected (sensor value is HIGH), it turns on the relay by setting the relayInput pin LOW.