Potentiometer and trimpot

A resistor whose value changes as you turn it.

Schematic letter: RV / VR
Unit / key rating: Ohm (Ω)

Pinout

1 and 3 (outer pins): Fixed resistance between them; tied to supply and GND.
2 (wiper): Gives a voltage or resistance that depends on the position.

Real photos

Different types of trimmer potentiometers

What is it for?

A potentiometer is a resistive track with a wiper (the middle pin) moving along it. The resistance between the two outer pins is fixed; the resistance between the wiper and either outer pin depends on the shaft position.

It's mostly used as a voltage divider: volume, brightness, a sensor's threshold. A trimpot is a small potentiometer on the board, set once with a screwdriver and left alone.

In a linear (B) pot the resistance changes evenly with angle; a logarithmic (A) type changes in a way that suits volume controls.

Things to watch out for

⚠ A crackling volume knob is a dirty pot: clean it with an oil-free contact cleaner.
⚠ Use a screwdriver that fits the trimpot exactly; the plastic body breaks easily.

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