ESP8266 - Potentiometer Relay

This build turns a potentiometer into a hands-on switch for anything plugged into a relay: a light bulb, an LED strip, a motor, an actuator. Turn the knob past a set point and the ESP8266 flips the relay on, turn it back and the relay drops out. It is a nice first project if you want to connect an analog input to a real-world load without touching any networking code.

The full tutorial, with every detail and the line-by-line code explanation, is on our site: ESP8266 - Potentiometer Relay

What you need

ESP8266 NodeMCU ESP-12F
ESP8266 D1 Mini NodeMCU ESP-12F
ESP8266 NodeMCU ESP-12E (Uno-form)
Micro USB Cable
ESP8266 NodeMCU ESP-12F (SMD-form)
USB Cable Type-A to Type-C (for USB-A PC)
USB Cable Type-C to Type-C (for USB-C PC)
Potentiometer
10k Ohm Trimmer Potentiometer
Potentiometer Kit
Potentiometer Module with Knob
Relay
Warning Light Bright Waterproof
DC Power Jack
Jumper Wires
Breadboard
Screw Terminal Expansion Board for ESP8266
DIYables Sensor Kit (18 sensors/displays)

Wiring

The potentiometer's wiper output goes to the ESP8266's analog pin, A0. The relay's control pin connects to D8. The relay itself sits between the ESP8266 and the actual load, like a warning light or motor, which typically runs on its own power, such as a 12V adapter, since the ESP8266's pins can't drive that directly. If you are not familiar with how a relay or a potentiometer is wired and powered, it is worth checking a dedicated tutorial for each component before wiring this project.

How it works

A potentiometer is a variable resistor: turning the knob changes the voltage the wiper outputs, which the ESP8266 reads as an analog value with analogRead(). A relay is an electrically controlled switch, it lets a low-voltage pin like D8 safely switch a separate, often higher-voltage or higher-current circuit, like a light bulb, on and off. In this project, the ESP8266 watches the potentiometer's value and uses it to decide when to energize the relay.

Code

The sketch sets RELAY_PIN as an output. In the loop, it reads the potentiometer with analogRead() and compares that value against ANALOG_THRESHOLD. Cross above the threshold and digitalWrite() sets the relay pin HIGH, turning the relay on; drop below it and the pin goes LOW, turning the relay off. A variant of the sketch does the same comparison but converts the analog reading to a voltage value first and compares against a voltage threshold instead of a raw analog value.

esp8266-potentiometer-relay.ino

/* * 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-potentiometer-relay */ #define POTENTIOMETER_PIN A0 // The ESP8266 pin connected to Potentiometer pin #define RELAY_PIN D8 // The ESP8266 pin connected to Relay's pin #define ANALOG_THRESHOLD 1000  void setup() { pinMode(RELAY_PIN, OUTPUT); // Configure the ESP8266 pin to the output mode } void loop() { int analog_value = analogRead(POTENTIOMETER_PIN); // read the input on analog pin if (analog_value > ANALOG_THRESHOLD) digitalWrite(RELAY_PIN, HIGH); // turn on Relay else digitalWrite(RELAY_PIN, LOW); // turn off Relay }