Arduino Nano - Ultrasonic Sensor - Relay

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

Arduino Nano activates the relay when the object is near the ultrasonic sensor
Arduino Nano deactivates the relay when the object is distant from the ultrasonic sensor

By linking a relay to a light bulb, LED strip, motor or actuator, we can use Arduino Nano and an ultrasonic sensor to manage the light bulb, LED strip, motor or actuator.

Hardware Preparation

1	×	Arduino Nano
1	×	USB A to Mini-B USB cable
1	×	Ultrasonic 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 Ultrasonic Sensor

If you are unfamiliar with relay and ultrasonic sensor (including pinout, operation, and programming), the following tutorials can help:

Wiring Diagram

This image is created using Fritzing. Click to enlarge 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-ultrasonic-sensor-relay */ #define TRIG_PIN 4 // The Arduino Nano pin connected to TRIG pin of ultrasonic sensor #define ECHO_PIN 3 // The Arduino Nano pin connected to ECHO pin of ultrasonic sensor #define RELAY_PIN 2 // The Arduino Nano pin connected to relay #define DISTANCE_THRESHOLD 50 // in centimeters float duration_us, distance_cm; void setup() { Serial.begin (9600); // Initialize the Serial to communicate with the Serial Monitor. pinMode(TRIG_PIN, OUTPUT); // set arduino pin to output mode pinMode(ECHO_PIN, INPUT); // set arduino pin to input mode pinMode(RELAY_PIN, OUTPUT); // set arduino pin to output mode } void loop() { // Produce a 10-microsecond pulse to the TRIG pin. digitalWrite(TRIG_PIN, HIGH); delayMicroseconds(10); digitalWrite(TRIG_PIN, LOW); // Measure the pulse duration from the ECHO pin duration_us = pulseIn(ECHO_PIN, HIGH); // calculate the distance distance_cm = 0.017 * duration_us; if (distance_cm < DISTANCE_THRESHOLD) digitalWrite(RELAY_PIN, HIGH); // turn on Relay else digitalWrite(RELAY_PIN, LOW); // turn off Relay // print the value to Serial Monitor Serial.print("distance: "); Serial.print(distance_cm); Serial.println(" cm"); delay(500); }

Detailed Instructions

Plug the USB cable into the Arduino Nano and the PC.
Launch the Arduino IDE, choose the correct board and port.
Open the code in the Arduino IDE.
Click the Upload button on the Arduino IDE to compile and upload the code to the Arduino Nano.

Move your hand in the vicinity of the sensor and observe the alteration in the state of the relay.

Code Explanation

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

※ NOTE THAT:

The code above is intended for educational purposes. The ultrasonic sensor is very susceptible to interference. If you plan to use it in a practical setting, noise filtering should be applied to the ultrasonic sensor. For more information on how to filter noise from distance measurements of the ultrasonic sensor, please refer to this tutorial.

Video Tutorial

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