Potentiometers
A Potentiometer
Potentiometers (often called pots) are variable Resistors - allowing for a wide range of resistance to be selected by turning a dial. A potentiometer’s resistance can vary from nearly 0Ω to its rated maximum, such as 10KΩ or 1MΩ.
Wiring summary: Connect the points of the circuit (such as those once joined with a resistor, or a key bending pair of points) to the middle pin and either the right or left pin (your choice). Turning the knob will vary the resistance between 0Ω and the potentiometer’s rating. If you need to ensure some resistance is always present, add an additional resistor in series.
More information:
A potentiometer is actually a long resistive strip and a wiper blade that is physically moved by the knob.
Symbol for Potentiometer
As the wiper moves, the resitance between it and each end of the strip changes. As a result, there are three pins - the middle pin is the wiper, the left pin is the left end of the resistive strip, and the right pin is the right end of the strip. The left pin is known as the counterclockwise pin, as turning the knob counterclockwise reduces the resitance and increases the current (and therefore volume, in the case of an amplifier) flowing between the left and middle pins. Likewise, the right pin is the clockwise pin, as turning the knob clockwise will allow more current to flow between the middle and right pins.
In a circuit with multiple paths, a potentiometer can therefore be used as a crossfader - as the resistance between left and middle pins is increased, the middle-to-right resistance decreases correspondingly.
Two types of potentiometers commonly sold are Linear Taper and Logarithmic Taper (aka the Audio Taper). With a Linear Taper pot, turning the dial halfway results in a resistance of 50% of the pot’s maximum. Audio Taper pots are a little more complex and are intended for use as volume controls in audio amplification circuits. Turning one of these halfway down results in only a 10-20% increase in resistance, corresponding to a 50% drop in sound volume to the human ear. Obviously, any circuit involving a volume control should use an audio taper pot, and other circuits may also benefit from fine control of resistance at the low end of the scale.