ESP32 - Light Sensor Triggers Relay

We are going to learn how to:

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

1×ESP-WROOM-32 Dev Module
1×Micro USB Cable
1×Light Sensor
1×10 kΩ resistor
1×Relay
1×Warning Light Bright Waterproof
1×12V Power Adapter
1×Breadboard
n×Jumper Wires
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About Relay and Light Sensor

If you do not have knowledge of relay and light sensor (pinout, how they work, how to connect them to ESP32, how to program for them...), learn about them in the following tutorials:

Wiring Diagram

ESP32 Light Sensor Relay Light Bulb Wiring Diagram

Image is developed using Fritzing. Click to enlarge image

ESP32 Code

/* * Created by esp32io.com * * This example code is in the public domain * * Tutorial page: https://esp32io.com/tutorials/esp32-light-sensor-triggers-relay */ // constants won't change const int LIGHT_SENSOR_PIN = A10; // ESP32 pin GIOP4 (ADC10) connected to light sensor's pin const int RELAY_PIN = 27; // ESP32 pin GIOP27 connected to Relay's pin const int ANALOG_THRESHOLD = 500; // variables will change: int analogValue; void setup() { pinMode(RELAY_PIN, OUTPUT); // set ESP32 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

  • If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE
  • Connect the ESP32 board to your PC via a micro USB cable
  • Open Arduino IDE, select the right ESP32 board and COM port
  • Copy the above code and paste it to Arduino IDE
  • Click Upload button on Arduino IDE to compile and upload code to ESP32 board
  • Arduino IDE Upload Code
  • 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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