Tech
Potentiometer Pinout, Types and Guide
Potentiometer Description
A potentiometer, often referred to as a “pot,” is a three-terminal variable resistor with a sliding or rotating contact that forms an adjustable voltage divider. It consists of a resistive element, typically made of carbon or a conductive plastic, with a sliding contact (wiper) that moves along the element, changing the resistance between the terminals.
When used as a voltage divider, one terminal is connected to a voltage source, the second terminal to ground, and the wiper provides an output voltage that varies between the source and ground as it is adjusted. Potentiometers are commonly used for adjusting levels in audio equipment, tuning circuits, and as user-adjustable control inputs in various electronic devices.
Potentiometer Working Principle
The working principle of a potentiometer involves varying the position of a sliding contact (wiper) along a resistive element to adjust the output voltage. When a voltage is applied across the two fixed terminals of the resistive element, the wiper, which moves along the element, picks off a variable voltage. This voltage is directly proportional to the wiper’s position relative to the fixed terminals. By adjusting the wiper, the resistance between the wiper and each terminal changes, allowing for precise control of the output voltage, which is a fraction of the input voltage.
Potentiometer Symbol
Potentiometer Pinout
Potentiometer Wiring Examples
- Potentiometer as a Simple Variable Resistor
When using a potentiometer as a simple variable resistor, you only need two pins: the middle pin (wiper) and one of the side pins. This setup allows you to adjust the resistance in a circuit easily.
For example, to dim an LED, you can connect the middle pin and one side pin of the potentiometer in series with the LED. As you turn the potentiometer’s shaft, the resistance increases or decreases, causing the LED to dim or brighten accordingly. It’s advisable to include an additional resistor in series to protect the LED from potential damage if the resistance is adjusted to zero.
- Connecting the Third Pin to the Middle
In some circuits, you may see the middle pin connected to one of the side pins. Although this connection does not change resistance, it is preferred by some because it avoids leaving an unconnected pin, which can make the circuit look neater.
- Potentiometer as Volume Control
Using all three pins of the potentiometer, you can create a voltage divider to control the volume of an audio amplifier. By wiring the potentiometer this way, you can adjust the input signal’s voltage. Turning the shaft decreases the voltage, thereby lowering the volume. This configuration is commonly used in audio equipment for smooth and effective volume control.
Potentiometer Types
Rotary Potentiometers
Rotary potentiometers are the most common type of potentiometer, featuring a resistive element and a rotating wiper that moves along this element to adjust resistance. The rotation of the wiper changes the resistance value, which is generally used for volume controls in audio equipment, tuning circuits in radios, and other devices requiring variable resistance.
Linear Potentiometers
Linear potentiometers operate on the same principle as rotary potentiometers but feature a straight, linear movement of the wiper instead of a rotating one. This design makes them particularly suitable for applications where precise linear motion is required, such as sliders on audio mixing desks, throttle controls, and other control panels. The straight-line movement allows for more accurate and intuitive control in scenarios where linear adjustment of resistance is needed.
Digital Potentiometers (DigiPots)
Digital potentiometers, or DigiPots, are electronically controlled potentiometers that replace the traditional mechanical wiper with digital signals to adjust resistance. They offer higher precision, programmability, and integration into automated systems, controlled via microcontrollers or other digital circuits such as the MPC555LFMZP40 32-bit microcontroller. DigiPots are commonly used in applications where remote control, repeatability, and fine adjustments are essential, such as in precision instrumentation, automated test equipment, and digitally controlled audio systems.
How To Use Potentiometers?
A potentiometer typically has three pins: two outer pins connected to a resistive element and a middle pin connected to a wiper that moves along the resistive element. When using a potentiometer as a simple variable resistor, you only need two pins—the middle pin and one of the side pins.
For example, in an LED dimming circuit, you can connect the middle pin to one end of the LED and one of the side pins to the positive terminal of the power supply. The other end of the LED connects to the negative terminal. Adjusting the potentiometer changes the resistance, thereby altering the brightness of the LED. To avoid zero resistance and potential damage to the LED, you might add a fixed resistor in series with the potentiometer.
In applications where you need a variable voltage output, such as volume control for audio equipment, you use the potentiometer as a voltage divider, which involves all three pins. One outer pin connects to the positive voltage supply, the opposite outer pin to the ground, and the middle pin provides the output voltage that varies between the supply voltage and ground depending on the wiper position.
For instance, in a volume control circuit, the audio source signal connects to one outer pin, the ground to the other outer pin, and the middle pin to the amplifier input. Adjusting the potentiometer changes the signal level sent to the amplifier, thus controlling the volume.
