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Arduino UNO R4 - Potentiometer

This tutorial instructs you how to use Arduino Uno R4 with a potentiometer. In detail, we will learn:

How a potentiometer works.
How to connect a potentiometer to Arduino UNO R4.
How to program Arduino UNO R4 to read values from the potentiometer and transform them into other usable values.

Hardware Preparation

1	×	Arduino UNO R4 WiFi
1	×	Arduino UNO R4 Minima (Alternatively)
1	×	USB Cable Type-C
1	×	Potentiometer
1	×	Potentiometer Kit
1	×	Breadboard
1	×	Jumper Wires
1	×	(Recommended) Screw Terminal Block Shield for Arduino UNO R4
1	×	(Recommended) Breadboard Shield For Arduino UNO R4
1	×	(Recommended) Enclosure For Arduino UNO R4

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

Overview of Potentiometer

A rotary potentiometer, also known as a rotary angle sensor, is used to manually change settings such as stereo volume, lamp brightness, or oscilloscope zoom level.

Pinout

A potentiometer typically has three pins.

GND pin: connect to GND (0V)
VCC pin: connect to VCC (5V or 3.3V)
Output pin: sends voltage to Arduino UNO R4's input pin.

※ NOTE THAT:

The GND pin and the VCC pin can be swapped.

How It Works

The potentiometer's shaft can turn from 0° (closest to the GND) up to a maximum angle (closest to the VCC pin), named ANGLE_MAX.

The voltage at the output pin varies from the voltage at GND to the voltage at VCC. The output voltage changes directly with the angle the shaft is turned.

When the angle is 0 degrees, the voltage at the output pin is 0 volts.
When the angle equals ANGLE_MAX, the voltage at the output pin matches the VCC's voltage.
If the angle is in between 0° and ANGLE_MAX, output_voltage = angle × VCC / ANGLE_MAX

※ NOTE THAT:

The value of ANGLE_MAX varies depending on the manufacturer. Usually, we don't pay much attention to the value of ANGLE_MAX unless we need to compute the angle of rotation (refer to the use cases section).

Arduino UNO R4 - Rotary Potentiometer

The pins A0 to A5 on the Arduino UNO R4 can be set up as analog inputs. These pins change the voltage, which ranges from 0 volts to VCC, into whole numbers between 0 and 1023. These numbers are called ADC values or analog values.

By connecting the output pin of a potentiometer to an analog input pin on the Arduino UNO R4, we can program the Arduino to read the ADC value and convert it into a useful number.

The value received by the Arduino UNO R4 is not an angle or voltage; it is an integer that ranges from 0 to 1023.

We take the number from the analog input pin and convert it into a different number. Now, let's see how it's used.

Use Cases

Converting the ADC value to the angle.
Converting the ADC value to the voltage
Converting the ADC value to a controllable value (like volume of stereo, brightness, or motor speed). This is the most frequently used scenario.

Rescale Range

		FROM		TO
Angle	rotated by user	0°	→	ANGLE_MAX
Voltage	from potentiometer's pin	0V	→	VCC
ADC value	read by Arduino UNO R4	0	→	1023
Other value	converted by Arduino UNO R4	VALUE_MIN	→	VALUE_MAX

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

How To Program For Potentiometer

Use the function analogRead() to read the value from a pin that is connected to the potentiometer's output pin.

adc_value = analogRead(A0);

Convert the ADC value to the angle of the potentiometer using the map() function.

angle = map(adc_value, 0, 1023, 0, ANGLE_MAX);

Convert the ADC value to the voltage:

voltage = map(adc_value, 0, 1023, 0, VCC);

Convert the ADC value to a manageable level (for example, the volume of the stereo, the brightness, or the speed of the DC motor).

value = map(adc_value, 0, 1023, VALUE_MIN, VALUE_MAX);

For example, adjusting the brightness of an LED. The brightness of an LED can be controlled using a PWM value from 0 (always OFF) to 255 (always ON). Therefore, we can map the ADC value to the LED brightness (from OFF to the brightest) as follows:

brightness = map(adc_value, 0, 1023, 0, 255);

※ NOTE THAT:

The map() function is used to change an analog value to either an int or long type value. If you need to work with a float type value, you should use the floatMap() function instead.

The 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 UNO R4 Code

/* * This Arduino UNO R4 code was developed by newbiely.com * * This Arduino UNO R4 code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-uno-r4/arduino-uno-r4-potentiometer */ float floatMap(float x, float in_min, float in_max, float out_min, float out_max) { // Map a float value from one range to another. return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min; } void setup() { // Begin serial communication with a baud rate of 9600: Serial.begin(9600); } void loop() { // Retrieve analog value from pin A0: int adc_value = analogRead(A0); // Convert the analog value to a voltage (0-5V range): float voltage = floatMap(adc_value, 0, 1023, 0, 5); // Output the analog value and corresponding voltage to the serial monitor: Serial.print("Analog: "); Serial.print(adc_value); Serial.print(", Voltage: "); Serial.println(voltage); // Wait for a second before repeating the loop: delay(1000); }

Detailed Instructions

Follow these instructions step by step:

If this is your first time using the Arduino Uno R4 WiFi/Minima, refer to the tutorial on setting up the environment for Arduino Uno R4 WiFi/Minima in the Arduino IDE.
Connect the potentiometer to Arduino Uno R4 according to the provided diagram.
Connect the Arduino Uno R4 board to your computer using a USB cable.
Launch the Arduino IDE on your computer.
Select the appropriate Arduino Uno R4 board (e.g., Arduino Uno R4 WiFi) and COM port.
Copy the code above and open it with Arduino IDE
Click the Upload button in Arduino IDE to upload the code to Arduino UNO R4

Open the Serial Monitor
Turn the potentiometer
Check the Serial Monitor for the result

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: 3.69 Analog: 906, Voltage: 4.43 Analog: 1023, Voltage: 5.00 Analog: 1023, Voltage: 5.00

Autoscroll Show timestamp

Clear output

9600 baud

Newline

Video Tutorial

Function References

Learn More

Arduino UNO R4 - Potentiometer fade LED

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