[Tutorial] Passive infrared (PIR) sensor with Arduino Uno

PIR sensor tutorial with Arduino Uno

1. Types

There are three types of PIR sensors with the different outlook to test: 

HC-SR501
Product Description: https://www.mpja.com/download/31227sc.pdf

UNO R3

2. Introduction

Pin Outs and Controls

The pin-outs and controls for this device are shown in the picture below and described in the following table.

Pin or Control	Function
Time Delay Adjust	Sets how long the output remains high after detecting motion. Anywhere from 5 seconds to 5 minutes.
Sensitivity Adjust	Sets the detection range.... from 3 meters to 7 meters
Trigger Selection Jumper	Set for single or repeatable triggers.
Ground pin	Ground input
Output Pin	Low when no motion is detected.. High when motion is detected. High is 3.3V
Power Pin	5 to 20 VDC Supply input

Device Area of Detection

Adjustment

PIR Range (Sensitivity) 

Time Delay

Mode Selection

The trigger mode selection jumper allows you to select between single and repeatable triggers.  The effect of this jumper setting is to determine when the time delay begins.

SINGLE TRIGGER – The time delay begins immediately when motion is first detected.

REPEATABLE TRIGGER –  Each detected motion resets the time delay.  Thus the time delay begins with the last motion detected.

Examples of the difference between distinct mode selection

In this first example, the time delay is set to three seconds and the trigger mode is set to single.  As you can see in the illustration below,  the motion is not always detected.   In fact, there is a period of about six seconds where motion cannot be detected. 

In the next example,  the time delay is still at three seconds and the trigger is set to repeatable.  In the illustration below, you can see that the time delay period is restarted.    However, after that three seconds, detection will still be blocked for three seconds. As I mentioned previously,  you could override the 3 second blocking period with some creative code,  but do give that consideration.  Some of the electronics you use may not like an on and then off jolt.  The three seconds allows for a little rest before starting back up.

3. Arduino HC-SR501 Motion Sensor Tutorial

• connection: it only requires three wires.

• sketch

The sketch simply turns on Your Arduino LED connected to Pin 13 whenever motion is detected. Be sure to beware of and somehow handle the 1 minute initialization in whatever application you develop.

// HC-SR501 Motion Detector

// Sample Sketch

int ledPin = 13;  // LED on Pin 13 of Arduino

int pirPin = 7; // Input for HC-S501

int pirValue; // Place to store read PIR Value

void setup() {

  

  pinMode(ledPin, OUTPUT);

  pinMode(pirPin, INPUT);

  digitalWrite(ledPin, LOW);

}

void loop() {

  pirValue = digitalRead(pirPin);

  digitalWrite(ledPin, pirValue);

}

Attention: no matter what modes, the delay time is at least 3-4 seconds.


More information refers to http://henrysbench.capnfatz.com/henrys-bench/arduino-sensors-and-input/arduino-hc-sr501-motion-sensor-tutorial/