SENSORS/ACTUATORS

INTERNET OF THING (IoT)

Arduino Nano ESP32 - Potentiometer

This tutorial provides instructions on how to use Arduino Nano ESP32 with the potentiometer. In detail, we will learn:

How the potentiometer works
How to interface Arduino Nano ESP32 with a potentiometer
How to program Arduino Nano ESP32 to read the value from a potentiometer
How to convert the value read from a potentiometer to the useful value

Hardware Preparation

1	×	Arduino Nano ESP32
1	×	USB Cable Type-C
1	×	Potentiometer
1	×	Breadboard
1	×	Jumper Wires
1	×	(Optional) DC Power Jack
1	×	(Recommended) Screw Terminal Adapter for Arduino Nano

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 provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you. We appreciate your support.

Overview of Potentiometer

The potentiometer (also known as rotary angle sensor) is used to change the settings (e.g. the speaker's volume, room's temperature, lamp's brightness...)

Potentiometer Pinout

A potentiometer usually has 3 pins:

VCC pin: connect this pin to VCC (5V or 3.3v)
GND pin: connect this pin to GND (0V)
Output pin: outputs the voltage to ESP32's input pin.

※ NOTE THAT:

The GND pin and VCC pin are interchangeable

How Potentiometer Works

The potentiometer's shaft can be rotated from 0° (closest to GND pin) to an angle (closest to VCC pin), called ANGLE_MAX.

The voltage in the output pin is in direct proportion to the angle position of the shaft, varing from 0 to VCC. The below table shows the relation between the angle and the voltage on the output pin:

Angle	Voltage
0°	0v
ANGLE_MAX°	VCC
angle°	angle° × VCC / ANGLE_MAX°

※ NOTE THAT:

The ANGLE_MAX value is depended on manufacturers.

Arduino Nano ESP32 - Rotary Potentiometer

The ESP32's analog input pin converts the voltage (between 0v and 3.3V) into integer values (between 0 and 4095), called ADC value or analog value.

We can connect the potentiometer's output pin to an ESP32's analog input pin, and then read the analog value from the pin.

The analog value from input pin can be rescaled into another value. Let's see the use cases:

Rescale the analog value to the potentiometer's angle.
Rescale the analog value to the potentiometer's voltage.
Rescale the analog value to the the setting value (e.g. the speaker's volume, room's temperature, lamp's brightness...)

Rescale Range

		FROM		TO
Angle	rotated by user	0°	→	ANGLE_MAX°
Voltage	from potentiometer's pin	0V	→	3.3V
ADC value	read by ESP32	0	→	4095
Setting value	converted by ESP32	VALUE_MIN	→	VALUE_MAX

Wiring Diagram between Potentiometer and Arduino Nano ESP32

The wiring diagram between Arduino Nano ESP32 and Potentiometer

This image is created using Fritzing. Click to enlarge image

How To Program Potentiometer

Read the value from an input pin, which connected to the output pin of the potentiometer by using analogRead() function.

analog_value = analogRead(A5); // A5

Rescale to the potentiometer's angle by using map() function.

angle = map(analog_value, 0, 4095, 0, ANGLE_MAX);

Rescale to the potentiometer's voltage:

voltage = map(analog_value, 0, 4095, 0, 3.3);

Rescale to the controllable value (e.g volume of stereo, brightness, speed of DC motor... )

value = map(analog_value, 0, 4095, VALUE_MIN, VALUE_MAX);

For example, rescaling to the brightness of LED. As mentioned in this tutorial, the brightness of LED can be controlled by using PWM value from 0 (always OFF) to 255 (always ON). Therefore, we can map the analog value to the brightness of LED (from OFF to the brightest) as follows:

brightness = map(analog_value, 0, 4095, 0, 255);

If you want to dim LED from the nightlight to the brightest,

nightlight = 100; // depending on your desired brightness brightness = map(analog_value, 0, 4095, nightlight, 255);

※ NOTE THAT:

The map() function can only be used to rescale the analog value to the int or long type value. If the controllable value is float type, you need to use the floatMap() function instead of the map() function.

floatMap() function:

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; }

Arduino Nano ESP32 Code

/* * This Arduino Nano ESP32 code was developed by newbiely.com * * This Arduino Nano ESP32 code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-nano-esp32/arduino-nano-esp32-potentiometer */ 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; } // the setup routine runs once when you press reset: void setup() { // Initialize the Serial to communicate with the Serial Monitor. Serial.begin(9600); } // the loop routine runs over and over again forever: void loop() { // read the input on analog pin A5: int analog_value = analogRead(A5); // Rescale to potentiometer's voltage (from 0V to 3.3V): float voltage = floatMap(analog_value, 0, 4095, 0, 3.3); // print out the value you read: Serial.print("Analog: "); Serial.print(analog_value); Serial.print(", Voltage: "); Serial.println(voltage); delay(1000); }

Detailed Instructions

If this is the first time you use Arduino Nano ESP32, see how to setup environment for Arduino Nano ESP32 on Arduino IDE.
Copy the above code and paste it to Arduino IDE.
Compile and upload code to Arduino Nano ESP32 board by clicking Upload button on Arduino IDE

Open Serial Monitor on Arduino IDE

How to open serial monitor on Arduino IDE

Rotate the potentiometer
Check out the result on the Serial Monitor. It looks like the below:

COM6

Send

Analog: 0, Voltage: 0.00 Analog: 0, Voltage: 0.00 Analog: 126, Voltage: 0.62 Analog: 281, Voltage: 1.37 Analog: 517, Voltage: 2.53 Analog: 754, Voltage: 3.2 Analog: 4095, Voltage: 3.30 Analog: 4095, Voltage: 3.30

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Clear output

9600 baud

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