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Arduino - Light Sensor Triggers Relay
We are going to learn how to:
- If the light sensor's analog value is lower than a threshold, turn relay on.
- If the light sensor's analog value is greater than a threshold, turn relay off.
By connecting relay to light bulb, led strip, motor or actuator... We can use the light sensor to control light bulb, led strip, motor or actuator...
Hardware Required
Or you can buy the following sensor kits:
| 1 | × | DIYables Sensor Kit (30 sensors/displays) | |
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
Disclosure: Some links in this section are Amazon affiliate links. If you make a purchase through these links, we may earn a commission at no extra cost to you.
Additionally, some links direct to products from our own brand, DIYables.
Additionally, some links direct to products from our own brand, DIYables.
About Relay and Light Sensor
If you do not know about relay and light sensor (pinout, how it works, how to program ...), learn about them in the following tutorials:
Wiring Diagram
This image is created 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-light-sensor-triggers-relay
*/
// constants won't change
const int LIGHT_SENSOR_PIN = A0; // Arduino pin connected to light sensor's pin
const int RELAY_PIN = 3; // Arduino pin connected to Relay's pin
const int ANALOG_THRESHOLD = 500;
// variables will change:
int analogValue;
void setup() {
pinMode(RELAY_PIN, OUTPUT); // set arduino pin to output mode
}
void loop() {
analogValue = analogRead(LIGHT_SENSOR_PIN); // read the input on analog pin
if(analogValue < ANALOG_THRESHOLD)
digitalWrite(RELAY_PIN, HIGH); // turn on Relay
else
digitalWrite(RELAY_PIN, LOW); // turn off Relay
}
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
- Radiates light to 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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