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Arduino - Ultrasonic Sensor - Relay
We are going to learn how to:
- If the object is close to ultrasonic sensor, turn relay on
- If the object is far from ultrasonic sensor, turn relay off
By connecting relay to light bulb, led strip, motor or actuator... We can use the ultrasonic sensor to control light bulb, led strip, motor or actuator...
Hardware Required
| 1 | × | Arduino UNO or Genuino UNO | |
| 1 | × | USB 2.0 cable type A/B | |
| 1 | × | Ultrasonic Sensor | |
| 1 | × | Relay | |
| 1 | × | Warning Light Bright Waterproof | |
| 1 | × | 12V Power Adapter | |
| n | × | Jumper Wires |
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About Relay and Ultrasonic Sensor
If you do not know about relay and ultrasonic sensor (pinout, how it works, how to program ...), learn about them in the following tutorials:
Wiring Diagram
Image is developed using Fritzing. Click to enlarge image
Arduino Code
/*
* Created by ArduinoGetStarted.com
*
* This example code is in the public domain
*
* Tutorial page: https://arduinogetstarted.com/tutorials/arduino-ultrasonic-sensor-relay
*/
// constants won't change
const int TRIG_PIN = 7; // Arduino pin connected to Ultrasonic Sensor's TRIG pin
const int ECHO_PIN = 6; // Arduino pin connected to Ultrasonic Sensor's ECHO pin
const int RELAY_PIN = 3; // Arduino pin connected to Relay's pin
const int DISTANCE_THRESHOLD = 50; // centimeters
// variables will change:
float duration_us, distance_cm;
void setup() {
Serial.begin (9600); // initialize serial port
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() {
// generate 10-microsecond pulse to TRIG pin
digitalWrite(TRIG_PIN, HIGH);
delayMicroseconds(10);
digitalWrite(TRIG_PIN, LOW);
// measure duration of pulse from 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);
}
Quick Steps
- Connect Arduino to PC via USB cable
- Open Arduino IDE, select the right board and port
- Copy the above code and open with Arduino IDE
- Click Upload button on Arduino IDE to upload code to Arduino
- Move your hand in front of sensor
- See the change of relay's state
Code Explanation
Read the line-by-line explanation in comment lines of source code!
Video Tutorial
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Ultrasonic Sensor and Relay on Commercial Products
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See Also
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