How do I connect a potentiometer to an Arduino?
Outer pins to 5V and GND, middle pin (the wiper) to an analog input such as A0. analogRead(A0) then returns 0 to 1023.
CIRCUIT DIAGRAM EXAMPLE
Arduino Potentiometer and LED Circuit Diagram
Reading a potentiometer and dimming an LED is the classic first analog input and output project on an Arduino. The diagram shows only the board pins the circuit uses, the way you would draw it in a project schematic.
How this circuit works
The potentiometer's two ends go to 5V and GND, so its track is a voltage divider across the supply. The wiper picks off any voltage between 0 and 5 V as you turn the knob, and A0 reads it.
The Uno's analog-to-digital converter turns 0 to 5 V into a number from 0 to 1023, about 4.9 mV per step. A 10 kΩ pot draws 0.5 mA and presents at most 2.5 kΩ at the wiper, under the 10 kΩ source resistance the Uno's ATmega328P is designed for.
D9 is one of the Uno's PWM pins. analogWrite(9, value) switches it between 0 and 5 V about 490 times a second, with value from 0 to 255 setting the fraction of time it is high. That is too fast to see, so the LED simply looks dimmer or brighter.
R1 limits the LED current while D9 is high to about (5 V − 2 V) / 220 Ω ≈ 14 mA, under the 20 mA usually recommended per Uno pin. The sketch needs one line in loop(): analogWrite(9, analogRead(A0) / 4), which scales the 0 to 1023 reading to the 0 to 255 PWM range.
Formulas
- Wiper voltage
VA0 = 5 V × wiper position (0 to 1)- ADC reading
reading = VA0 / 5 V × 1023- LED current while D9 is high
I = (5 V − 2 V) / 220 Ω ≈ 14 mA- Average LED current with PWM
Iavg ≈ 14 mA × value / 255At analogWrite(9, 128) the LED averages about 7 mA.
Parts list
| Ref | Part | Value | What it does |
|---|---|---|---|
| A1 | IC / module | Arduino Uno | Arduino Uno. Only the four pins the circuit uses are drawn. |
| D1 | LED | Red | Red LED, anode toward R1. |
| R1 | Resistor | 220 Ω | 220 Ω LED resistor. |
| RV1 | Potentiometer | 10 kΩ | 10 kΩ linear potentiometer. |
Netlist
Recovered from the drawing itself: every pin on each net below is joined by a wire, a junction or a shared supply or ground symbol.
| Net | Connects |
|---|---|
| N1 | A1.A0, RV1.wiper |
| N2 | A1.D9, R1.1 |
| N3 | A1.5V, RV1.1 |
| GND | A1.GND, RV1.3, D1.K |
| N4 | R1.2, D1.A |
Common mistakes
- Wiring the wiper to 5V or GND. The wiper goes to A0 and the outer pins to 5V and GND; otherwise turning the knob to one end shorts the supply.
- Using a pin without PWM. On an Uno only pins 3, 5, 6, 9, 10 and 11 support analogWrite; on other pins the LED is just on or off.
- Leaving out R1. The LED then draws as much as the pin can push, which can damage both.
- Using a logarithmic (audio) pot. The reading then changes unevenly across the knob's travel; a linear pot gives an even response.
Build notes
- Sketch: analogWrite(9, analogRead(A0) / 4); maps 0–1023 from the pot to 0–255 PWM.
Frequently asked questions
Why divide analogRead by 4?
analogRead returns 0 to 1023 (10 bits) but analogWrite takes 0 to 255 (8 bits). Dividing by 4 maps one range onto the other; map(value, 0, 1023, 0, 255) does the same.
Which Arduino Uno pins support PWM?
Pins 3, 5, 6, 9, 10 and 11, marked with a ~ on the board.
Does this work on an ESP32 or another 3.3 V board?
Yes, with the pot's top end on 3.3 V instead of 5 V and a smaller LED resistor, about 100 Ω. The ESP32 reads 0 to 4095 by default because its ADC is 12-bit.
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