Potentiometers and Trimmers for Makers: Types, Tapers, Wiring, and Pots vs Encoders

Every maker electronics guide on this site walks you through resistors, capacitors, diodes, and transistors — but the potentiometer, the single most common way humans adjust an electronic circuit by hand, rarely gets its own treatment. Volume knobs, brightness dimmers, calibration trimmers buried on a PCB, joystick axes, and the throttle on that FPV transmitter you built are all potentiometers doing slightly different jobs. This guide covers how pots actually work, the tapers and formats you'll encounter, how to wire one correctly (including the three-terminal vs two-terminal trap that burns out drivers), and when a rotary encoder is the better choice instead.

What a Potentiometer Actually Is

A potentiometer is a resistive element — usually carbon film, cermet, or conductive plastic — with a wiper that slides or rotates along it, tapping off a variable fraction of the total resistance. It has three terminals: two ends of the resistive track, and the wiper. Used across all three terminals, it's a voltage divider — the configuration you want for volume knobs, sensor calibration, and anything feeding an analog input. Used with only the wiper and one end terminal, it acts as a variable resistor (a rheostat) — useful for current limiting, but riskier, because if the wiper loses contact (common as pots wear), you get an open circuit instead of a defined voltage.

TypeFormatTypical UseNotes Rotary potentiometerPanel-mount knob, single turnVolume, speed, brightness controlsMost common; 270° rotation typical Slide potentiometerLinear travelAudio mixer faders, lighting controlsProne to dust ingress over the track Trimmer (trim pot)PCB-mount, screwdriver-adjustCalibration set-once values (reference voltage, offset trim)Not rated for frequent adjustment Multi-turn trimmerPCB-mount, 10-25 turnsPrecision calibrationFine resolution, used in power supplies, sensor trim Digital potentiometer (digipot)IC, e.g. MCP41010Microcontroller-adjustable "pot"No mechanical wear, but limited resolution and current handling

Understanding Taper: Linear vs Audio (Logarithmic)

Taper describes how resistance changes as you turn the shaft. A linear taper pot changes resistance proportionally with rotation — turn it 50% and you get 50% of the resistance. This is what you want for anything feeding a linear measurement: a joystick axis, a sensor calibration trim, a light dimmer where you want even brightness steps.

An audio (logarithmic) taper changes resistance on a curve that matches how human hearing perceives loudness — we hear volume logarithmically, not linearly, so a linear pot on a volume control feels like all the change happens in the last 10% of rotation. Audio taper pots are wired specifically for volume controls and marked "A" (audio) vs "B" (linear) on many datasheets — but this convention isn't universal, so always check the datasheet rather than assuming.

Wiring a Potentiometer as a Voltage Divider

For reading a pot with a microcontroller ADC (Arduino, ESP32, etc.), wire all three terminals: one outer terminal to your reference voltage (3.3V or 5V), the other outer terminal to ground, and the wiper to your ADC input pin. The wiper voltage then swings smoothly from 0V to your reference voltage as you turn the knob — this is the safe, standard way to read a pot and it never produces an undefined state.

Add a small filter capacitor (0.1µF from wiper to ground) if your readings are noisy — pot wipers pick up switching noise easily, especially near stepper drivers or SMPS circuits.
Never exceed the pot's power rating — most panel pots are rated 0.1-0.5W. At 5V across a 10kΩ pot, that's only 2.5mW dissipated, well within spec, but check before using a pot as a rheostat carrying real current (e.g. as a dimmer for an incandescent bulb — don't do this, use a proper PWM dimmer circuit instead).
ESP32 ADC nonlinearity: the ESP32's ADC is notoriously non-linear near 0V and near VREF. If you need accurate low-end readings from a pot, either use the ADC's calibration API (esp_adc_cal) or shift your working range away from the extremes.

Pot vs Rotary Encoder: Which One Do You Actually Want

This is the decision point most beginners get wrong, so it's worth being explicit:

Use a Potentiometer When...Use a Rotary Encoder When... You need an absolute position (the knob always represents the same value at the same angle)You need relative adjustment (turn right to increase, doesn't matter where you started) Limited rotation is fine (270° typical)You want infinite rotation Simple analog read is acceptable (one ADC pin)You're fine reading two digital pins and debouncing in software Mechanical wear over years of use isn't a dealbreakerYou want a component that won't drift or wear the resistive track out

Volume knobs on synthesizers that need to "remember" position on power-up are usually pots. Menu-scroll knobs on 3D printer touchscreens and radios are almost always encoders. See this site's Rotary Encoders for Makers guide for the encoder side of that comparison.

Common Failure Modes

Scratchy audio pots (that crackling sound when you turn a volume knob) come from oxidation or dust contamination on the resistive track breaking wiper contact intermittently. A shot of contact cleaner (not WD-40, which leaves a residue that attracts more dust) through the vent slots, worked in by rotating the pot fully several times, fixes most cases. If a trimmer pot won't hold calibration or drifts under vibration, it's usually worn out from being adjusted too many times — trimmers are rated for a limited number of adjustment cycles (often just a few hundred to a few thousand), not continuous use.

Choosing Values

10kΩ is the de facto default for general-purpose voltage-divider use with microcontrollers — low enough that input impedance of the ADC doesn't meaningfully load it, high enough that it doesn't waste significant current. Audio circuits commonly use 10kΩ-100kΩ. For rheostat/current-limiting duty, calculate the value from Ohm's law against your actual load current and voltage, and always check the pot's power rating against I²R at your working current.

Potentiometers are unglamorous, but getting the taper, wiring, and value right the first time saves you a redesign later — and knowing when to reach for an encoder instead will save you from fighting a component that was never the right tool for the job.

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