Arduino Nano - Motion Sensor - Relay

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

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×Warning Light Bright Waterproof
1×12V Power Adapter
1×DC Power Jack
1×Jumper Wires
1×(Optional) 9V Power Adapter for Arduino Nano
1×(Recommended) Screw Terminal Adapter 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)
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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

The wiring diagram between Arduino Nano and Motion Sensor Relay

This image is created using Fritzing. Click to enlarge image

Initial Setting

Time Delay AdjusterScrew it in anti-clockwise direction fully.
Detection Range AdjusterScrew it in clockwise direction fully.
Repeat Trigger SelectorPut jumper as shown on the image.
arduino motion sensor initial setting

Arduino Nano Code

/* * This Arduino Nano code was developed by * * This Arduino Nano code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * */ #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.
Arduino IDE Upload Code

Code Explanation

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

Video Tutorial


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