Potentiometer
A potentiometer divides a voltage by the position of its wiper. Microcontrollers read it as an analog input; analog circuits read it as a variable resistor.
A resistive track runs between two end terminals; a wiper rides along the track and taps off a fraction of the voltage. Linear or audio-tapered tracks let you choose how the resistance changes with rotation.
In plain terms
A volume knob you can hear with electrons. Twist it and the resistance from one end to the wiper smoothly changes.
Also called: pot, variable resistor.
Why designers use it
- Volume and tone controls in audio gear.
- Live calibration — set a trim once at the factory.
- User-adjustable thresholds and setpoints.
Best for
- Volume / brightness controls
- Calibration trimmers
- Position feedback
When not to use it
- Where digital UX is expected — a rotary encoder fits modern interfaces better.
- Where dust or vibration would degrade contact — encoders or hall sensors win.
Common mistakes
- Loading the wiper too heavily and bending the divider's response.
- Confusing audio vs linear taper for the wrong feel.
Where you will find it
- The volume knob on a guitar amp or stereo is just a variable resistor in disguise — turning it changes how much of the audio signal reaches the speaker, which is exactly why louder is 'more electrical signal'.
- Game-controller analogue sticks are two pots crossed at 90°; pushing the stick rotates both wipers and the console reads two voltages — that pair is your character's joystick direction.
- Faders on a recording-studio mixing console are linear pots six inches long; an engineer's hand on a fader is literally moving a wiper that changes how loud each microphone sounds in the final mix.
A short history
The potentiometer as a voltage-dividing resistance measurement instrument was described by Charles Wheatstone in 1843, building on the slide-wire potential-divider concept. The rotary variable resistor ('pot') used for volume control in radio sets was commercialised in the 1920s, with carbon-film elements becoming standard by the 1930s. Wirewound potentiometers for precision applications were produced by Bourns and Helipot (a Beckman division) from the 1940s onward. Today digital potentiometers (e.g. Microchip MCP41010) implement the variable-resistance function in silicon using a resistor ladder and wiper switch, enabling software-controlled analogue settings without mechanical wear.
Good to know
- Volume knobs use a 'logarithmic' (audio-taper) pot because human hearing is logarithmic — a linear pot would feel mostly silent until the last 30 % of rotation.
- Bourns trimmer pots survive ~200 adjustments before drift sets in — they're meant for factory calibration, not user tuning.