ESP32 - Potentiometer Triggers Servo Motor

This tutorial instructs you how to use ESP32 with the potentiometer to control servo motor. In detail:

The ESP32 automatically rotates a servo motor to 90° if the potentiometer's analog value is above a threshold
The ESP32 automatically rotates a servo motor to back to 0° if the potentiometer's analog value is under a threshold

We also learn how to convert the analog value to voltage and then use the voltage threshold to control the LED:

The ESP32 automatically rotates a servo motor to 90° if the potentiometer's voltage is above a threshold.
The ESP32 automatically rotates a servo motor back to 0° if the potentiometer's voltage is under a threshold.

If you want to control the angle of servo motor in proportion to the value of potentiometer, see ESP32 - Servo motor controlled by potentiometer tutorial

Hardware Used In This Tutorial

1	×	ESP-WROOM-32 Dev Module
1	×	USB Cable Type-C
1	×	Potentiometer
1	×	(Alternative) Potentiometer Kit
1	×	(Alternative) Potentiometer Module with Knob
1	×	Servo Motor
1	×	Breadboard
1	×	Jumper Wires
1	×	(Optional) DC Power Jack
1	×	(Recommended) Screw Terminal Expansion Board for ESP32
1	×	(Recommended) Power Splitter For ESP32

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

Disclosure: Some of the links in this section are Amazon affiliate links, meaning we may earn a commission at no additional cost to you if you make a purchase through them. Additionally, some links direct you to products from our own brand, DIYables.

Introduction to Servo Motor and Potentiometer

We have specific tutorials about servo motor and potentiometer. Each tutorial contains detailed information and step-by-step instructions about hardware pinout, working principle, wiring connection to ESP32, ESP32 code... Learn more about them at the following links:

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

If you're unfamiliar with how to supply power to the ESP32 and other components, you can find guidance in the following tutorial: How to Power ESP32.

ESP32 Code - Analog Threshold

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-potentiometer-triggers-servo-motor */ #include <Servo.h> #define POTENTIOMETER_PIN 36 // ESP32 pin GPIO36 (ADC0) connected to Potentiometer pin #define SERVO_PIN 26 // ESP32 pin GPIO26 connected to Servo Motor's pin #define ANALOG_THRESHOLD 1000 Servo servo; // create servo object to control a servo void setup() { // set the ADC attenuation to 11 dB (up to ~3.3V input) analogSetAttenuation(ADC_11db); servo.attach(SERVO_PIN); // attaches the servo on pin 9 to the servo object servo.write(0); } void loop() { int analogValue = analogRead(POTENTIOMETER_PIN); // read the input on analog pin if (analogValue > ANALOG_THRESHOLD) servo.write(90); // rotate servo motor to 90 degree else servo.write(0); // rotate servo motor to 0 degree }

Quick Instructions

If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
Do the wiring as above image.
Connect the ESP32 board to your PC via a micro USB cable
Open Arduino IDE on your PC.
Select the right ESP32 board (e.g. ESP32 Dev Module) and COM port.
Click to the Libraries icon on the left bar of the Arduino IDE.
Type ServoESP32 on the search box, then look for the servo library by Jaroslav Paral. Please be aware that both version 1.1.1 and 1.1.0 are affected by bugs. Kindly choose a different version.
Click Install button to install servo motor library for ESP32.

Copy the above code and paste it to Arduino IDE.
Compile and upload code to ESP32 board by clicking Upload button on Arduino IDE
Rotate the potentiometer
See servo motor rotating

ESP32 Code - Voltage Threshold

The analog value read from the potentiometer is converted to voltage, and then the voltage is compared to a voltage threshold. If it exceeds the threshold, it triggers a servo motor

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-potentiometer-triggers-servo-motor */ #include <Servo.h> #define POTENTIOMETER_PIN 36 // ESP32 pin GPIO36 (ADC0) connected to Potentiometer pin #define SERVO_PIN 26 // ESP32 pin GPIO26 connected to Servo Motor's pin #define VOLTAGE_THRESHOLD 2.5 // Voltages Servo servo; // create servo object to control a servo void setup() { // set the ADC attenuation to 11 dB (up to ~3.3V input) analogSetAttenuation(ADC_11db); servo.attach(SERVO_PIN); // attaches the servo on pin 9 to the servo object servo.write(0); } void loop() { int analogValue = analogRead(POTENTIOMETER_PIN); // read the input on analog pin float voltage = floatMap(analogValue, 0, 1023, 0, 5); // Rescale to potentiometer's voltage if (voltage > VOLTAGE_THRESHOLD) servo.write(90); // rotate servo motor to 90 degree else servo.write(0); // rotate servo motor to 0 degree } float floatMap(float x, float in_min, float in_max, float out_min, float out_max) { return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min; }

※ NOTE THAT:

This tutorial uses the analogRead() function to read values from an ADC (Analog-to-Digital Converter) connected to a potentiometer. The ESP32 ADC is good for projects that do NOT need high accuracy. However, for projects that need precise measurements, please note:

The ESP32 ADC is not perfectly accurate and might need calibration for correct results. Each ESP32 board can be a bit different, so you need to calibrate the ADC for each individual board.
Calibration can be difficult, especially for beginners, and might not always give the exact results you want.

For projects that need high precision, consider using an external ADC (e.g ADS1115) with the ESP32 or using an Arduino, which has a more reliable ADC. If you still want to calibrate the ESP32 ADC, refer to ESP32 ADC Calibration Driver

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