Introduction: Arduino Basics: PIR Sensors
Welcome to the next installment of Arduino Basics!
This instructable will teach you how to use a PIR sensors with the arduino, and we wil build a simple motion detector!
Step 1: Supplies
For this instructable you will need the following:
1 arduino (with protoshield to make life easy)
1 LED of any color
1 PIR sensor from Parallax (you can find these at most radio shacks)
Solid wire to hook it up
Step 2: Setup
The wiring is pretty simple, the PIR sensor has screen printed: + - out
Hook the + to 5v, - to ground and out to pin 7
The take the LED and put power to pin 8 and ground to ground.
If its confusing, take a look at the pictures!
Step 3: Code
This code is lifted from the arduino.cc site here, the code I used is also attached.
You can see from the code, the sensor first calibrates itself and then watches for movement. When it detects movement, the blue light goes on. You can watch the serial monitor to see how long the movement lasts.
Step 4: Further Projectse
After these steps you have a very simple motion detector. From here you can use the PIR sensor to trigger events (like a siren or a text message that someone is in your room).
I just chose to use it to protect my stunnaz from blue light fearing monsters. It seems to work so far....
Please post your PIR sensor projects below and stay tuned for even more Arduino Basics!

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67 Comments
5 years ago
Hi
Good explanation, program works fine.
But its better to use 330 ohms in series with the LED
thanks to the atmel controller the circuit survives, With other controllers you are less Lucky.
best regards
Gerard
7 years ago
What does pirstate=HIGH mean in the code?
Reply 6 years ago
it means pir sensor ill on, after its detected something
6 years ago
I have made the program like that and the sensor have been active in serial monitor. But, the LED can't be light up. Are there any solution to fix this?
6 years ago
Thanks for the info, I will try this out, code looks good. Thanks again
6 years ago
int ledPin1 = 13; // choose the pin for the LED
int ledPin2 = 12;
int ledPin3 = 11;
int ledPin4 = 10;
int inputPin = 9; // choose the input pin (for PIR sensor)
int inputPin2 = 8;
int buzzerPin = 7;
int switchPin = 6; //pin for door sensor1
int switchPin2 = 5; // pin for door sensor2
int pirState1 = LOW;
int pirState2 = LOW;
int val = 0;
int val2 = 0;
int magnetState = LOW;
int magnetState2 = LOW;
int magnetValState = 0;
int magnetValState2 = 0;
void setup() {
pinMode(ledPin1, OUTPUT); // declare LED as output
pinMode(ledPin2, OUTPUT); // declare LED as output
pinMode(ledPin3, OUTPUT);
pinMode(inputPin, INPUT); // declare sensor 1 as input
pinMode(inputPin2, INPUT); // declare sensor 2 as input
pinMode(buzzerPin, OUTPUT);
pinMode(switchPin, INPUT);
pinMode(switchPin2, INPUT);
digitalWrite(switchPin, HIGH);
digitalWrite(switchPin2, HIGH);
Servo1.attach(servoPin);
Serial.begin(9600);
}
void loop() {
val = digitalRead(inputPin); // read input value
if (val == HIGH) { // check if the input is HIGH
digitalWrite(ledPin1, HIGH); // turn LED ON
magnetValState = digitalRead(switchPin);
if (digitalRead(switchPin) == HIGH) {
digitalWrite(ledPin2, HIGH);
delay(1500);
digitalWrite(ledPin2, LOW);
delay(1500);
digitalWrite(buzzerPin, HIGH);
Serial.println("Door brake!");
}
if (pirState1 == LOW) {
// we have just turned on
Serial.println("Motion detected!");
// We only want to print on the output change, not state
pirState1 = HIGH;
}
}
// check sensor 2 after delay
val2 = digitalRead(inputPin2);
if (val2 == HIGH) {
digitalWrite(ledPin3, HIGH);
magnetValState2 = digitalRead(switchPin2);
if (digitalRead(switchPin2) == HIGH) {
digitalWrite(ledPin4, HIGH);
delay(50);
digitalWrite(ledPin4, LOW);
delay(50);
digitalWrite(buzzerPin, HIGH);
Serial.println("Door brake!");
}
if(pirState2 == LOW) {
// we have just turned on
Serial.println("Motion from sensor 2 detected!");
// We only want to print on the output change, not state
pirState2 = HIGH;
}
} else {
digitalWrite(ledPin1, LOW); // turn LED OFF
delay (50);
digitalWrite(ledPin2, LOW); // may be already
//playTone(0, 0);
delay(50);
digitalWrite(ledPin3, LOW); // turn LED OFF
delay (50);
digitalWrite(ledPin4, LOW); // turn LED OFF
delay (50);
if (pirState1 == HIGH) {
// we have just turned of
Serial.println("Motion ended!");
// We only want to print on the output change, not state
pirState1 = LOW;
}
if (pirState2 == HIGH) {
// we have just turned of
Serial.println("Motion ended!");
// We only want to print on the output change, not state
pirState2 = LOW;
}
}
}
someone please help me,how can i combine two pir sensor with two door sensor? im trying this coding,but only sensor 2 detected...
6 years ago
resistor needed across the LED?
6 years ago
I Want to make a Human / living being detector, not a motion detector. How to do that and what should be the changes in code ?
6 years ago
good..................
7 years ago
Can PIR motion sensor and arduino nano work together?
7 years ago
Hi,
I have been wondering a few things.
1 does it output only high or low or is there a way to read a numeric value?
2 is it possible to use two pirs and follow the movement according to the 2 pirs, so if more right reading it looks more to the right and left same story.
If anyone knows a pointer for me to look in it is very much appreciated.
Keep up the good work.
7 years ago
I utilized my on board SMD led pin 13. Nice instructions.
7 years ago
PIR sensor implemented for alarm car alarm system
7 years ago
please can you send me a code i am using a pir
7 years ago
I am useing an aurdwendo i need a code can you please help me
7 years ago
hai in my PIR sensor the output pin always goes high even when there is
no motion,I also altered the sensitivity and delay,but there is no
change! any one help me plzz!..
7 years ago
i am starting arduino please help me to interface sensors
7 years ago
hello when I change the "long unsigned int pause = 5000;"
I do not see any change in how long the led stays on.
In fact regardless of how I long set it, it will only stay on for 2 seconds.
7 years ago
pir.pde:98:37: error: invalid operands of types 'long unsigned int' and 'int()' to binary 'operator-'
This error is presented whenever i tried to verify/upload this code.. Help Me! T_T
7 years ago
Great info! thanks
Next time, and for other sensors connection you can use Circuito.io, it's a free tool to generate schematics and code