How to Use Potentiometer: Examples, Pinouts, and Specs

A potentiometer, commonly referred to as a "pot," is a three-terminal variable resistor where the resistance is manually adjustable by turning a knob or sliding a fader. It is widely used in electronics to vary the voltage and control the current in a circuit. Potentiometers are often utilized for adjusting settings such as volume in audio systems, brightness in lighting applications, and calibration in measurement devices.

• Resistance Range: Typically from 1 ohm to 1 megaohm
• Tolerance: ±10% to ±20% of nominal resistance
• Power Rating: Usually between 0.1W to 0.5W for standard pots
• Voltage Rating: Dependent on the material and design, often up to a few hundred volts
• Temperature Coefficient: Varies with material, typically around ±100 ppm/°C
• Linear or Logarithmic Taper: Determines how the resistance changes as the pot is turned

To use a potentiometer in a circuit:

1. Voltage Divider: Connect pin 1 to the higher voltage, pin 3 to the lower voltage (often ground), and pin 2 will provide a variable voltage output between these two levels.
2. Variable Resistor: Connect pin 2 to one of the outer pins (1 or 3), leaving the other outer pin unconnected. This creates a two-terminal variable resistor.

• Avoid Exceeding Ratings: Do not exceed the voltage and power ratings to prevent damage.
• Clean Environment: Use in a clean environment to avoid dust and dirt affecting the wiper contact.
• Mounting: Ensure secure mounting to prevent mechanical stress that could affect performance.
• End Stops: Do not force the knob beyond its end stops to avoid mechanical damage.

The following example demonstrates how to read the analog value from a potentiometer connected to an Arduino UNO.

// Define the pin connected to the potentiometer wiper (middle terminal)
const int potPin = A0;

void setup() {
  // Initialize serial communication at 9600 bits per second:
  Serial.begin(9600);
}

void loop() {
  // Read the value from the potentiometer
  int potValue = analogRead(potPin);
  // Convert the reading (which goes from 0 - 1023) to a voltage (0 - 5V):
  float voltage = potValue * (5.0 / 1023.0);
  // Print out the value in volts
  Serial.println(voltage);
  // Delay for a bit to get stable readings
  delay(250);
}

• Inconsistent Output: If the output voltage is erratic, check for dirt or wear in the potentiometer track.
• Crackling Noise in Audio Applications: This could be due to a dirty wiper contact. Try using a contact cleaner.
• No Variation in Output: Ensure that all connections are secure and that the potentiometer is not damaged.

Q: Can I use a potentiometer to control the speed of a motor? A: Yes, but ensure the potentiometer can handle the current required by the motor.

Q: How do I choose between a linear and logarithmic potentiometer? A: Use a linear potentiometer when you need a uniform change in resistance. Use a logarithmic potentiometer for audio applications where the human ear perceives sound logarithmically.

Q: What is the difference between a potentiometer and a rheostat? A: A rheostat is a two-terminal variable resistor used for high-power applications, while a potentiometer is a three-terminal device used for lower power applications and provides a variable voltage output.

Q: How do I clean a potentiometer? A: Use a non-conductive cleaner specifically designed for electronic components. Apply it to the track and rotate the wiper across its full range several times.