Potentiometer Circuit Diagram

Potentiometer Circuit Diagram — interactive diagram. Open it in the editor to customise components and wiring.

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A potentiometer is a three-terminal resistive voltage divider whose adjustable wiper produces a variable output voltage proportional to its rotational or linear position.

A potentiometer — commonly shortened to 'pot' — is a variable resistor with three terminals: two fixed end terminals spanning the full resistance element, and a third moving contact called the wiper. When all three terminals are used, the device functions as a voltage divider; when only one end terminal and the wiper are used, it functions as a simple variable resistor (rheostat).

In a voltage-divider configuration, the supply voltage Vcc is applied across the two end terminals (pins 1 and 3). The wiper (pin 2) divides the resistive element into two portions: R_upper and R_lower, where R_upper + R_lower always equals the total rated resistance R_total. The output voltage at the wiper is described by the voltage-divider equation:

V_out = Vcc × (R_lower / R_total)

When the wiper is at the mid-point, V_out = Vcc / 2. At one extreme, V_out approaches 0 V; at the other extreme, V_out approaches Vcc. The output tracks linearly with wiper position for a linear-taper (lin) pot, or logarithmically for an audio-taper (log/audio) pot — the latter chosen because human perception of loudness is logarithmic.

Load impedance critically affects accuracy. If the downstream load (an ADC input, op-amp, or measuring circuit) presents a low resistance Z_load relative to R_lower, it forms a parallel combination with R_lower that disturbs the divider ratio and introduces error. The rule of thumb is: Z_load should be at least 10× R_total for the error to remain below roughly 10%. High-impedance CMOS ADC inputs and op-amp non-inverting inputs satisfy this easily; low-impedance loads require a buffer stage (voltage follower) between the wiper and the load.

Potentiometers are used in audio volume controls, sensor calibration trimming, position sensing (rotary encoders in analogue form), and adjustable reference voltage generation for comparator circuits. Wirewound types handle higher power; carbon-track types are economical for low-power signal duties; conductive-plastic elements offer superior resolution and life in precision applications.

Mechanical wear is the principal failure mode — the resistive track degrades at the wiper contact point, producing scratchy noise (audio) or erratic ADC readings (control circuits). Trimmer potentiometers (trimpots) are sealed multi-turn devices intended for one-time calibration, not repeated adjustment.

How to wire potentiometer circuit diagram

Identify the three terminals of the potentiometer Look at the underside of the pot body. The two outer pins (pins 1 and 3) are the fixed end terminals connected to each end of the resistive element. The centre pin (pin 2) is the wiper. Use a multi-meter in resistance mode to confirm: measure across pins 1 and 3 to read total resistance; measure 1-to-2 and 2-to-3 and confirm they sum to the total as you rotate the shaft.
Connect the supply voltage across the end terminals Apply Vcc to one end terminal (pin 1 or pin 3) and GND to the opposite end terminal. Either orientation is valid — reversing supply and ground simply reverses the direction in which the output voltage changes as the shaft turns. Note: the supply must not exceed the potentiometer's maximum voltage rating.
Take the output from the wiper terminal Connect the wiper (pin 2) to the downstream circuit — ADC input, op-amp input, or measuring instrument. Verify that the load impedance is significantly higher than the pot's total resistance to avoid loading error.
Add a bypass capacitor across the supply if in a noisy environment In circuits where the potentiometer is near switching power supplies or digital circuits, a 100 nF ceramic capacitor placed directly across the Vcc and GND supply rails at the pot reduces high-frequency noise riding on the wiper output.
Verify output range with a multi-meter Set a multi-meter to DC volts and measure between the wiper pin and GND. Rotate the shaft from one extreme to the other. Output should sweep from near 0 V to near Vcc without discontinuity. Any dead spots, jumps, or scratchy behaviour indicate a worn or contaminated track.

Specifications

Typical resistance range	100 Ω to 1 MΩ (signal-level panel pots); 10 Ω to 100 kΩ (trimpots)
Taper options	Linear (B/LIN), Logarithmic/Audio (A/LOG), Reverse-logarithmic (C)
Power rating	0.1 W to 2 W (carbon film); up to 10 W+ (wirewound panel types)
Maximum wiper current	1–5 mA (carbon film); 10–50 mA (wirewound)
Voltage-divider formula	V_out = Vcc × (R_lower / R_total)
Mechanical life (rotary)	Typically 10,000–100,000 cycles (carbon film); up to 1,000,000 cycles (conductive plastic)
Applicable standard	IEC 60393 (potentiometers for use in electronic equipment)

Safety warnings

Do not apply a voltage across the potentiometer end terminals that exceeds its rated maximum voltage. Exceeding this causes resistive track breakdown, localised heating, and potential fire in enclosed assemblies.
Do not draw current through the wiper terminal in excess of the pot's rated wiper current — typically 1–5 mA for carbon-film types. Excessive wiper current accelerates track wear and causes thermal damage.
When using a potentiometer in a mains-voltage control application (lamp dimmer, motor speed), ensure the component is specifically rated for that purpose, housed in an appropriate enclosure, and that the work complies with IEC 60364, BS 7671, NEC/NFPA 70, or AS/NZS 3000. A signal-level pot must never be substituted in a mains circuit.
In precision measurement circuits, static discharge from rotating the shaft can momentarily exceed the voltage rating of sensitive downstream components. Consider anti-static handling and ESD protection if working with high-impedance CMOS inputs.

Tools needed

Digital multi-meter (resistance and DC voltage modes)
Breadboard and jumper wires for prototyping
DC power supply or regulated voltage source
Oscilloscope (optional, to observe wiper noise under rotation)
Soldering iron and solder (for PCB-mounted pots)
Anti-static wrist strap (when handling sensitive CMOS circuits)

Common mistakes

Using only two terminals (one end and the wiper) when a voltage-divider output is required — omitting the second supply connection means the output cannot rise above or fall below the single connected rail.
Selecting a pot with a resistance far too low for the load, causing heavy current draw through the element, power dissipation beyond its rating, and a load-dependent (non-linear) output.
Confusing audio-taper and linear-taper pots — an audio-taper pot used in a position-sensing circuit will produce a non-linear output curve that mimics a fault condition.
Leaving the wiper terminal unconnected while measuring across the two end terminals and concluding the pot is broken — the end-to-end resistance reading is always the rated value regardless of wiper position.
Routing the wiper signal wire in parallel with high-current switching lines, coupling noise onto the analogue output and corrupting ADC readings.

Troubleshooting

Output voltage does not reach 0 V or Vcc at the shaft extremes: Cause: The resistive element has a small residual resistance at each end (typically a few ohms to tens of ohms). This is normal and is specified as the 'end resistance' in the datasheet. Fix: If the residual voltage causes an application error, use a software or hardware offset/calibration, or select a pot with a lower specified end resistance. Alternatively, apply a slightly wider supply range than the required output range.
Output voltage is noisy or scratchy when shaft is rotated: Cause: The resistive track is worn or contaminated with dust and oxidation at the wiper contact point. Fix: Clean the track with appropriate electrical contact cleaner spray through the vent slot (if accessible). If noise persists, the pot requires replacement. For audio circuits, a log-taper pot with a sealed housing resists contamination better.
Output voltage is non-linear or does not match the voltage-divider formula: Cause: Low load impedance is forming a parallel combination with the lower resistive segment, distorting the divider ratio. Fix: Measure the load impedance and compare it to the pot's total resistance. If Z_load < 10× R_total, insert a buffer amplifier (voltage follower) between the wiper and the load.

Frequently asked questions

What is the difference between a potentiometer and a rheostat?

Both use the same three-terminal component. A potentiometer uses all three terminals to create a voltage divider. A rheostat uses only two terminals — one end and the wiper — to present a variable series resistance. Rhetostats are used for current control; potentiometers for voltage division.

Why does the output voltage change when I connect a load to the potentiometer wiper?

The load resistance appears in parallel with the lower portion of the pot's resistance element, reducing the effective lower resistance and pulling the output voltage down. Use a load whose impedance is at least 10 times the potentiometer's total resistance, or add a buffer amplifier (voltage follower) to isolate the wiper from the load.

What is a linear-taper versus an audio-taper (log) potentiometer?

A linear-taper pot changes resistance proportionally to shaft rotation — halfway around gives half the resistance. An audio-taper (logarithmic) pot changes resistance logarithmically, so the output rises steeply at first then levels off, matching the logarithmic perception of human hearing. Use linear taper for position sensing or reference voltage; use audio taper for volume controls.

Can a potentiometer handle high current or high power directly?

Standard carbon-track pots are rated for milliampere-level wiper currents and typically 0.05–0.5 W total. Wirewound potentiometers can handle higher power, but even then they are not suitable for direct power control. Use a pot as a low-current signal control driving a power device such as a MOSFET, transistor, or op-amp.

How do I read the resistance value printed on a potentiometer body?

The value is usually printed directly — for example '10K' means 10 kΩ. Some smaller trimpots use a three-digit code similar to resistors: '103' means 10 × 10³ = 10 kΩ. The taper is often indicated by a letter suffix: 'B' or 'LIN' for linear, 'A' or 'LOG' for audio/logarithmic taper.