Situatie

A PIR (Passive Infrared) sensor detects motion by measuring changes in infrared radiation emitted by objects (like humans or animals) within its field of view.

PIR sensors are commonly used for:

Component	Quantity	Notes
Arduino Uno (or Nano, Mega, etc.)	1	Any compatible board
PIR Motion Sensor (HC-SR501 or similar)	1	Adjustable sensitivity and delay
Breadboard	1	For easy connections
Jumper wires	~5	Male-to-male recommended
LED	1	Optional for visual indication
220Ω resistor	1	For LED current limiting
USB cable	1	For programming and power

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 Understanding the PIR Sensor

Typical PIR module (e.g., HC-SR501) has 3 pins:

Pin	Label	Function
1	VCC	Power (connect to +5V)
2	OUT	Sends HIGH when motion is detected
3	GND	Connects to Ground

Adjustable knobs (optional):

• Sensitivity: changes detection range (typically 3–7 meters)
• Time delay: how long output stays HIGH after motion (usually 0.3s–5min)

Wiring Diagram

PIR Sensor	Arduino	Notes
VCC	5V	Power supply
OUT	D2	Digital input pin
GND	GND	Common ground
LED (+)	D13	Visual output (optional)
LED (–)	GND (via 220Ω resistor)	Current limit

Connect VCC → 5V, GND → GND, OUT → D2, LED → D13 (optional)

Arduino Code Example


// PIR Motion Sensor with LED Example

int pirPin = 2; // PIR sensor output pin
int ledPin = 13; // LED pin

int pirState = LOW; // Default state
int val = 0; // Variable for reading the pin status

void setup() {
pinMode(pirPin, INPUT);
pinMode(ledPin, OUTPUT);
Serial.begin(9600);
Serial.println("PIR Motion Sensor Active");
}

void loop() {
val = digitalRead(pirPin); // Read input value from PIR

if (val == HIGH) {
digitalWrite(ledPin, HIGH); // Turn LED ON
if (pirState == LOW) {
Serial.println("Motion detected!");
pirState = HIGH;
}
} else {
digitalWrite(ledPin, LOW); // Turn LED OFF
if (pirState == HIGH) {
Serial.println("Motion ended!");
pirState = LOW;
}
}
}


Explanation: The PIR output goes HIGH when motion is detected. The LED turns on and a message is printed to the Serial Monitor.

How It works

1. Warm-up time: After powering up, the PIR sensor takes ~30–60 seconds to stabilize.
2. Detection: When an object moves, the sensor’s output pin goes HIGH.
3. Reset: After the set delay, the output returns LOW until new motion is detected.

1. Control a Relay

Use motion detection to control a light or appliance:

int relayPin = 8; // connect to relay module IN pin
// Replace ledPin with relayPin in code

2. Buzzer Alarm

Add a buzzer that sounds when motion is detected:

int buzzerPin = 9;
digitalWrite(buzzerPin, HIGH);

3. Serial Logging

Send motion logs to a computer or IoT platform for analysis.

4. Automation

Combine PIR with an LDR (light sensor) so it only triggers lights at night.

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Solutie

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