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 site , the code I used is also attached.
/*
*
//////////////////////////////////////////////////
*
//making sense of the Parallax PIR sensor's output
*
//////////////////////////////////////////////////
*
*
Switches a LED according to the state of the sensors output pin.
*
Determines the beginning and end of continuous motion sequences.
*
*
@author: Kristian Gohlke / krigoo (_) gmail (_) com / http://krx.at
*
@date: 3. September 2006
*
* kr1
(cleft) 2006
*
released under a creative commons "Attribution-NonCommercial-ShareAlike
2.0" license
*
*
*
* The
Parallax PIR Sensor is an easy to use digital infrared motion sensor module.
*
*
* The
sensor's output pin goes to HIGH if motion is present.
*
However, even if motion is present it goes to LOW from time to time,
*
which might give the impression no motion is present.
* This
program deals with this issue by ignoring LOW-phases shorter than a given time,
*
assuming continuous motion is present during these phases.
*
*/
/////////////////////////////
//VARS
//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 =
7; //the digital pin connected to the PIR sensor's output
int ledPin =
8;
/////////////////////////////
//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);
}
}
}
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.