ESP32 - Motion Sensor - Relay

This tutorial instructs you how to use ESP32 with HC-SR501 motion sensor and relay. In detail, ESP32 automatically turns on relay if the motion is detected, and turn off relay if otherwise.

We can extend this tutorial to use the motion sensor to control a led strip, siren, light bulb, or actuator... by connnecting them to the relay.

Hardware Used In This Tutorial

1	×	ESP-WROOM-32 Dev Module
1	×	USB Cable Type-C
1	×	HC-SR501 Motion Sensor
1	×	Relay
1	×	(Optional) Solenoid Lock
1	×	(Optional) 12V Active Buzzer
1	×	(Optional) 12V Cooling Fan
1	×	(Optional) 12V Warning Light Bright Waterproof
1	×	12V Power Adapter
1	×	Breadboard
1	×	Jumper Wires
1	×	(Optional) DC Power Jack
1	×	(Recommended) Screw Terminal Expansion Board for ESP32

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

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Introduction to Relay and Motion Sensor

We have specific tutorials about relay and motion sensor. Each tutorial contains detailed information and step-by-step instructions about hardware pinout, working principle, wiring connection to ESP32, ESP32 code... Learn more about them at the following links:

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

If you're unfamiliar with how to supply power to the ESP32 and other components, you can find guidance in the following tutorial: How to Power ESP32.

Initial Setting


Detection Range Adjuster	Fully screw it in the clockwise direction.
Time Delay Adjuster	Fully screw it in the anti-clockwise direction.
Repeat Trigger Selector	Put jumper like the below image.

ESP32 Code

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-motion-sensor-relay */ #define MOTION_SENSOR_PIN 22 // ESP32 pin GPIO22 connected to the OUTPUT pin of motion sensor #define RELAY_PIN 26 // ESP32 pin GPIO26 connected to Relay's pin int motionStateCurrent = LOW; // current state of motion sensor's pin int motionStatePrevious = LOW; // previous state of motion sensor's pin void setup() { Serial.begin(9600); // initialize serial pinMode(MOTION_SENSOR_PIN, INPUT); // set ESP32 pin to input mode pinMode(RELAY_PIN, OUTPUT); // set ESP32 pin to output mode } void loop() { motionStatePrevious = motionStateCurrent; // store old state motionStateCurrent = digitalRead(MOTION_SENSOR_PIN); // read new state if (motionStatePrevious == LOW && motionStateCurrent == HIGH) { // pin state change: LOW -> HIGH Serial.println("Motion detected!, turns relay ON"); digitalWrite(RELAY_PIN, HIGH); // turn on } else if (motionStatePrevious == HIGH && motionStateCurrent == LOW) { // pin state change: HIGH -> LOW Serial.println("Motion stopped!, turns relay OFF"); digitalWrite(RELAY_PIN, LOW); // turn off } }

Quick Instructions

If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
Do the wiring as above image.
Connect the ESP32 board to your PC via a micro USB cable
Open Arduino IDE on your PC.
Select the right ESP32 board (e.g. ESP32 Dev Module) and COM port.
Copy the above code and paste it to Arduino IDE.
Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE

Move your hand in front of sensor
See the change of relay's state

Line-by-line Code Explanation

The above ESP32 code contains line-by-line explanation. Please read the comments in the code!

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