Catalog / Potentiometer Cheat Sheet
Potentiometer Cheat Sheet
A concise guide to potentiometers, covering types, applications, specifications, and practical usage. This cheat sheet provides essential information for electronics enthusiasts and engineers working with these variable resistors.
Potentiometer Basics
Definition
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A potentiometer (or pot) is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. |
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It acts as a variable resistor, allowing you to adjust the resistance value by turning a knob or slider. |
Symbol
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https://upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Potentiometer_symbols.svg/1280px-Potentiometer_symbols.svg.png |
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Schematic symbol for potentiometer |
Key Components
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Resistive Element: |
A track of resistive material (carbon composition, cermet, wirewound) determining the total resistance. |
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Wiper (Sliding Contact): |
A movable contact that slides along the resistive element, tapping off a fraction of the total resistance. |
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Terminals: |
Three terminals: two connected to the ends of the resistive element, and one connected to the wiper. |
Operation
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By adjusting the position of the wiper, the resistance between the wiper and one end terminal changes. This allows a fraction of the applied voltage to be tapped off. |
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When used as a potentiometer, all three terminals are connected. When used as a variable resistor (rheostat), only two terminals are used (one end and the wiper). |
Types of Potentiometers
Based on Resistive Material
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Carbon Film: |
Low cost, general purpose, higher noise. Typically used in audio controls and low-precision applications. |
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Cermet: |
Good stability, higher precision, lower noise than carbon film. Used in precision circuits and trimmers. |
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Wirewound: |
High power rating, high precision, but limited resolution. Used in high-power applications and precision control. |
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Conductive Plastic: |
Low noise, long life, moderate precision. Used in high-end audio equipment and precision controls. |
Based on Mechanical Configuration
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Rotary Potentiometers: |
Adjusted by rotating a shaft. Common in volume controls, user interfaces. |
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Slider Potentiometers: |
Adjusted by sliding a knob linearly. Used in audio mixers and graphic equalizers. |
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Trimmer Potentiometers (Trimpots): |
Small potentiometers designed for infrequent adjustments, often used for calibration purposes on PCBs. |
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Multi-turn Potentiometers: |
Require multiple rotations of the shaft to cover the full resistance range, allowing for finer adjustments. Used in precision instrumentation. |
Key Specifications
Electrical Characteristics
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Total Resistance: |
The overall resistance between the two end terminals, typically ranging from a few ohms to several megaohms. |
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Tolerance: |
The allowable variation in the total resistance, expressed as a percentage (e.g., ±10%). |
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Power Rating: |
The maximum power the potentiometer can dissipate without damage, typically expressed in watts. |
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Taper (Linear/Logarithmic): |
Describes the relationship between the wiper position and the resistance. Linear taper means resistance changes linearly with position; logarithmic taper (audio taper) means resistance changes logarithmically. |
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Resolution: |
The smallest possible change in resistance that can be achieved. Wirewound pots have lower resolution than film pots. |
Environmental Considerations
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Temperature Coefficient: |
Describes how much the resistance changes with temperature. Important for high-precision applications. |
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Operating Temperature Range: |
The range of temperatures within which the potentiometer will function correctly. |
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Humidity Sensitivity: |
How much the resistance changes with humidity. |
Applications
Common Uses
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Volume controls in audio equipment. |
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Brightness/contrast adjustments in displays. |
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Calibration trimmers in circuits. |
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Position feedback sensors in robotics. |
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Adjustable voltage dividers. |
Circuit Examples
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Voltage Divider: |
A potentiometer connected to a voltage source provides an adjustable output voltage. |
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Rheostat: |
A potentiometer used as a two-terminal variable resistor can control current in a circuit (e.g., dimming an LED). |
Practical Considerations
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Always select a potentiometer with a suitable power rating for the application to prevent overheating. |
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Consider the required precision and stability when choosing between different potentiometer types (e.g., carbon film vs. cermet). |
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Use a linear taper for general-purpose adjustments and a logarithmic taper (audio taper) for volume controls. |