ESP8266 - Light Sensor Relay

This tutorial instructs you how to use ESP8266 and light sensor to trigger relay. In detail:

ESP8266 activates the relay if the analog value of the light sensor is below a threshold.
ESP8266 deactivates the relay if the analog value of the light sensor is above a threshold.

By connecting a relay to a light bulb, LED strip, motor, or actuator, we can use an ESP8266 and a light sensor to regulate the light bulb, LED strip, motor, or actuator.

The light sensor is also known as photoresistor, light-dependent resistor, photocell, LDR. The ESP8266 uses a light sensor to measure the ambient light level. If the light is low, the ESP8266 activates the relay, and if it's high, the relay turns off.

Hardware Preparation

1	×	ESP8266 NodeMCU
1	×	USB Cable Type-C
1	×	Light Sensor
1	×	10 kΩ resistor
1	×	Relay
1	×	Warning Light Bright Waterproof
1	×	12V Power Adapter
1	×	DC Power Jack
1	×	Breadboard
1	×	Jumper Wires
1	×	(Recommended) Screw Terminal Expansion Board for ESP8266
1	×	(Recommended) Power Splitter For ESP8266 Type-C

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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Additionally, some of these links are for products from our own brand, DIYables.

Overview of Relay and Light Sensor

If you are not familiar with relay and light sensor (including pinout, functioning, programming ...), the following tutorials can help you:

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

See more in ESP8266's pinout and how to supply power to the ESP8266 and other components.

ESP8266 Code

/* * This ESP8266 NodeMCU code was developed by newbiely.com * * This ESP8266 NodeMCU code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp8266/esp8266-light-sensor-relay */ #define LIGHT_SENSOR_PIN A0 // The ESP8266 pin connected to light sensor #define RELAY_PIN D8 // The ESP8266 pin connected to Relay #define ANALOG_THRESHOLD 500 void setup() { pinMode(RELAY_PIN, OUTPUT); // Configure the ESP8266 pin to the output mode } void loop() { int analog_value = analogRead(LIGHT_SENSOR_PIN); // read the value on analog pin if (analog_value < ANALOG_THRESHOLD) digitalWrite(RELAY_PIN, HIGH); // turn on Relay else digitalWrite(RELAY_PIN, LOW); // turn off Relay }

Detailed Instructions

To get started with ESP8266 on Arduino IDE, follow these steps:

Check out the how to setup environment for ESP8266 on Arduino IDE tutorial if this is your first time using ESP8266.
Wire the components as shown in the diagram.
Connect the ESP8266 board to your computer using a USB cable.
Open Arduino IDE on your computer.
Choose the correct ESP8266 board, such as (e.g. NodeMCU 1.0 (ESP-12E Module)), and its respective COM port.
Connect an ESP8266 to your computer using a USB cable.
Launch the Arduino IDE, select the correct board and port.
Copy the code above and open it with the Arduino IDE.
Click the Upload button in the Arduino IDE to compile and upload the code to the ESP8266.

Emit light source towards the sensor
Check out the relay's state

Code Explanation

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

Video Tutorial

Learn More

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