Arduino Nano - Motion Sensor - Relay

This tutorial instructs you how to use Arduino Nano and motion sensor to control relay. In detail:

Arduino Nano activates the relay if motion is detected by the motion sensor
Arduino Nano deactivates the relay if no motion is detected by the motion sensor

By connecting a relay to a light bulb, LED strip, motor, or actuator.. We can use the Arduino Nano and motion sensor to control the light bulb, LED strip, motor, or actuator...

This can be applied in an automation process that triggers actions upon detecting human presence.

Hardware Preparation

1	×	Arduino Nano
1	×	USB A to Mini-B USB cable
1	×	HC-SR501 Motion Sensor
1	×	Relay
1	×	Warning Light Bright Waterproof
1	×	12V Power Adapter
1	×	DC Power Jack
1	×	Jumper Wires
1	×	Breadboard
1	×	(Recommended) Screw Terminal Expansion Board for Arduino Nano
1	×	(Recommended) Breakout Expansion Board for Arduino Nano
1	×	(Recommended) Power Splitter For Arduino Nano

Or you can buy the following sensor kits:

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

Disclosure: Some of the links provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you.
Additionally, some of these links are for products from our own brand, DIYables .

Overview of Relay and Motion Sensor

If you are unfamiliar with relay and motion sensor (including pinout, functioning, programming, etc.), the following tutorials can help:

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

See The best way to supply power to the Arduino Nano and other components.

Initial Setting


Time Delay Adjuster	Screw it in anti-clockwise direction fully.
Detection Range Adjuster	Screw it in clockwise direction fully.
Repeat Trigger Selector	Put jumper as shown on the image.

Arduino Nano Code

/* * This Arduino Nano code was developed by newbiely.com * * This Arduino Nano code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-nano/arduino-nano-motion-sensor-relay */ #define MOTION_SENSOR_PIN 3 // The Arduino Nano pin connected to the OUTPUT pin of motion sensor #define RELAY_PIN 2 // The Arduino Nano pin connected to the relay module int motion_state = LOW; // current state of motion sensor's pin int prev_motion_state = LOW; // previous state of motion sensor's pin void setup() { Serial.begin(9600); // Initialize the Serial to communicate with the Serial Monitor. pinMode(MOTION_SENSOR_PIN, INPUT); // set arduino pin to input mode pinMode(RELAY_PIN, OUTPUT); // set arduino pin to output mode } void loop() { prev_motion_state = motion_state; // store old state motion_state = digitalRead(MOTION_SENSOR_PIN); // read new state if (prev_motion_state == LOW && motion_state == HIGH) { // pin state change: LOW -> HIGH Serial.println("Motion detected!"); digitalWrite(RELAY_PIN, HIGH); // turn on } else if (prev_motion_state == HIGH && motion_state == LOW) { // pin state change: HIGH -> LOW Serial.println("Motion stopped!"); digitalWrite(RELAY_PIN, LOW); // turn off } }

Detailed Instructions

Connect your Arduino Nano to your computer using a USB cable.
Launch the Arduino IDE, select the appropriate board and port.
Copy the code provided and open it in the Arduino IDE.
Click the Upload button in the Arduino IDE to compile and upload the code to the Arduino Nano.

Code Explanation

Check out the line-by-line explanation contained in the comments of the source code!

Video Tutorial

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