ESP32 S3 UNO - Potentiometer
This ESP32 S3 Uno potentiometer tutorial shows you how to wire a potentiometer to the ESP32 S3 Uno form board and read its value with Arduino code. As you turn the knob of this variable resistor (also called a rotary angle sensor), the Serial Monitor shows the analog value and the matching voltage.
In this tutorial, you will:
- Learn how a potentiometer works and what its three pins do
- Wire a potentiometer to an analog pin of the ESP32 S3 Uno
- Read the analog value (0 to 4095) with analogRead()
- Convert the value into a voltage, an angle, or any range you need
Hardware Preparation
Or you can buy the following kits:
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
Additionally, some of these links are for products from our own brand, DIYables .
Overview of Potentiometer
A potentiometer is one of the easiest ways to give your project a manual control. Once you know how it turns a knob position into a voltage, you can use it for almost any setting.
A rotary potentiometer is also called a rotary angle sensor. You find it in everyday devices, where it sets things like the volume of a stereo, the brightness of a lamp, or the zoom level of an oscilloscope.
Pinout
Most potentiometers have three pins. Two of them are for power, and the middle one gives the signal you read.
GND pin
Connect it to GND (0V).
VCC pin
Connect it to the power supply. With the ESP32 S3 Uno, use the 3.3V pin, so the output never goes above 3.3V.
Output pin
This pin sends a voltage to an analog input pin of the ESP32 S3 Uno.
※ NOTE THAT:
You can swap the GND pin and the VCC pin. The only change is the direction: turning the knob the same way will now make the value go down instead of up.
How It Works
Inside the potentiometer, a sliding contact moves along a resistor as you turn the shaft. This simple idea turns a position into a voltage that your board can measure.
The shaft turns from 0° (the end closest to the GND pin) up to a maximum angle (the end closest to the VCC pin). We call this maximum angle ANGLE_MAX.
The voltage on the output pin goes from the GND voltage to the VCC voltage, and it changes in a straight line with the angle. At 0°, the output is 0V. At ANGLE_MAX, the output equals VCC. For any angle in between, output_voltage = angle × VCC / ANGLE_MAX.
※ NOTE THAT:
ANGLE_MAX is different from one manufacturer to another. You usually do not need it, unless you want to calculate the rotation angle (see the use cases below).
ESP32 S3 Uno - Rotary Potentiometer
The ESP32 S3 Uno has analog input pins on the A0 to A5 headers. These pins measure a voltage and turn it into a number, so this is where the potentiometer's output goes.
The ESP32 S3 Uno has a 12-bit ADC. It turns a voltage from 0V to about 3.3V into a whole number from 0 to 4095. This number is called the ADC value or the analog value. Keep in mind that the board does not give you an angle or a voltage directly. It only gives you this number.
When you wire the potentiometer's output pin to an analog pin, your code can read the ADC value and convert it into something useful.
Use Cases
There are three common ways to use the ADC value. You can convert it into the angle of the shaft, or into the voltage on the output pin. Most often, you convert it into a value you want to control, such as the volume of a stereo, the brightness of an LED, or the speed of a motor.
Rescale Range
The table below shows how each range lines up with the others. The idea is always the same: one end of the knob gives the minimum, the other end gives the maximum.
| FROM | TO | |||
|---|---|---|---|---|
| Angle | rotated by user | 0° | → | ANGLE_MAX |
| Voltage | from potentiometer's pin | 0V | → | VCC (3.3V) |
| ADC value | read by ESP32 S3 Uno | 0 | → | 4095 |
| Other value | converted by ESP32 S3 Uno | VALUE_MIN | → | VALUE_MAX |
ESP32 S3 Uno Pinout
The image below shows the pinout diagram of the ESP32 S3 Uno form board. Use it to find the Uno header pins (D2, A0, SDA…) and their GPIO numbers when you wire the circuit.
Wiring Diagram
Connect the potentiometer's output pin to the A0 header of the ESP32 S3 Uno, and power the potentiometer from the 3.3V pin.
This image is created using Fritzing. Click to enlarge image
| Potentiometer Pin | ESP32 S3 Uno Pin |
|---|---|
| VCC | 3.3V |
| GND | GND |
| Output | A0 (GPIO2) |
WARNING
The ESP32 S3 Uno GPIO pins are NOT 5V tolerant. If you connect the potentiometer's VCC pin to 5V, the output pin can reach 5V and damage GPIO2. Always power the potentiometer from 3.3V.
How To Program For Potentiometer
Reading a potentiometer takes one function, and converting the result takes one more. The snippets below show each step on its own.
- Read the output pin with analogRead(). The A0 header is GPIO2, so you pass the number 2.
- Convert the ADC value into the angle of the shaft with the map() function.
- Convert the ADC value into a voltage.
- Convert the ADC value into a value you want to control, such as the volume of a stereo, the brightness of an LED, or the speed of a DC motor.
- For example, to set the brightness of an LED, you use a PWM value from 0 (always OFF) to 255 (always ON). Map the ADC value onto this range, and the knob moves the LED from off to fully bright.
※ NOTE THAT:
The map() function only works with whole numbers, so it returns an int or long value. When you need a float result, such as a voltage with decimals, use the floatMap() function instead.
Here is the floatMap() function:
ESP32 S3 Uno Code
This sketch reads the potentiometer on GPIO2 once every second. It converts the raw value into a voltage between 0V and 3.3V with floatMap(), then prints both numbers on the Serial Monitor.
The line analogSetAttenuation(ADC_11db); in setup() is important on the ESP32 S3 Uno. By default, its ADC can only measure a small voltage. With 11 dB attenuation, the analog pin reads the full range from 0V up to about 3.3V. Without it, the reading hits 4095 too early, and the values look wrong as you turn the knob.
Detailed Instructions
Follow these steps in order:
- New to the ESP32 S3 Uno? Follow ESP32 S3 Uno - Getting Started first.
- Wire it up as shown in the diagram.
- Connect the board to your computer with a USB Type-C cable.
- Open Arduino IDE, choose the ESP32S3 Dev Module board and the correct COM port.
- Copy the code above and paste it into Arduino IDE.
- Upload the code by clicking the Upload button.
- Open the Serial Monitor and set the baud rate to 9600.
- Turn the potentiometer slowly from one end to the other.
- Check the result on the Serial Monitor.
- Tip: The ESP32 S3 Uno ADC is a bit noisy, so the value may jump by a few steps even when you do not touch the knob. This is normal. If you need a steadier number, read the pin several times and use the average.
Video Tutorial
Watch the video below to see this ESP32 S3 Uno project step by step.
Function References
FAQ
Why does my potentiometer read 0 to 4095 instead of 0 to 1023?
The ESP32 S3 Uno has a 12-bit ADC, so analogRead() returns a number from 0 to 4095. Many Arduino boards, like the UNO R4 by default, use a 10-bit range of 0 to 1023. If you copy code from those boards, change every 1023 in your map() calls to 4095.
Why does the code call analogSetAttenuation(ADC_11db)?
It sets the input range of the ESP32 S3 Uno ADC to about 0V to 3.3V, so the full turn of the potentiometer maps to 0 to 4095. Without it, the range is smaller and the reading reaches 4095 long before the knob reaches the end. The UNO R4 does not need this line, because it is only needed on ESP32 boards like the ESP32 S3 Uno. Keep the potentiometer powered from 3.3V so the signal never goes above 3.3V.
Can I power the potentiometer from 5V on the ESP32 S3 Uno?
No. With 5V on the VCC pin, the output pin can reach 5V, and the ESP32 S3 Uno pins are not 5V tolerant. This can damage the pin. Use the 3.3V pin instead.
Which ESP32 S3 Uno pins can read a potentiometer?
The A0 to A5 headers all work as analog inputs (GPIO2, GPIO1, GPIO7, GPIO6, GPIO5 and GPIO4). Many digital headers, such as D2 to D7 and D10 to D13, also support analog input. In your code, always write the GPIO number, for example analogRead(2) for A0. Note that D8 (GPIO21) and D9 (GPIO46) have no analog function.
Why do the readings near 0V and 3.3V look less accurate?
The ESP32 S3 Uno ADC is not perfectly linear at the very ends of its range. Values close to 0V and close to 3.3V can be a little off. For a knob control this does not matter, but for exact voltage measurement, take the middle of the range or calibrate your readings.
What if my project needs more potentiometers than the Uno headers give?
The ESP32 S3 Uno has two extra rows of holes with more GPIOs. GPIO15 and GPIO16 support I/O, PWM and analog. GPIO45 and GPIO35 to GPIO42 support I/O and PWM. GPIO47 and GPIO48 are output only, with PWM. Solder pin headers to use them and write the GPIO number in your code. For extra potentiometers, use GPIO15 or GPIO16, because they are the only extra pins that can read analog values. Keep two warnings in mind. First, GPIO47 and GPIO48 may run at 1.8V instead of 3.3V on some modules (especially ones with "V" in the name, like R8V or R16V), so 3.3V devices can be damaged or act strangely. Second, GPIO0, GPIO3 (D6), GPIO45 and GPIO46 (D9) are boot strapping pins, and a wrong connection can stop the board from booting or uploading code. Use the other extra pins first.
Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| No COM port shows up in Arduino IDE | USB driver missing or board not in upload mode | Install the CP210x or CH340 driver, use a data USB cable, or hold BOOT while pressing RESET |
| Nothing prints on the Serial Monitor | Wrong baud rate | Set the Serial Monitor to 9600 baud |
| Value stays at 0 when you turn the knob | VCC wire missing or output wire on the wrong pin | Check the 3.3V and GND wires and make sure the middle pin goes to A0 (GPIO2) |
| Value reaches 4095 when the knob is only half turned | ADC attenuation not set | Add analogSetAttenuation(ADC_11db) in setup() |
| Value jumps around without touching the knob | ADC noise or a loose breadboard contact | Press the wires in firmly and average several readings |
| Value goes down when you turn the knob up | VCC and GND pins are swapped | Swap the two outer wires or change the map() range |
| Voltage shows more than 3.3V in your math | Code still uses 5V or 1023 from old Arduino code | Use 3.3 and 4095 in floatMap() and map() |