Potentiometer

From Combat Robot

A potentiometer is a variable resistor that can be used to control power flow through a circuit.

The present popular usage of the term potentiometer (or 'pot' for short) describes an electrical device which has a user-adjustable electrical resistance. Usually, this is a three-terminal resistor with a sliding contact in the center (the wiper). If only two terminals are used (one side and the wiper), it acts as a variable resistor. Its shortcoming is that of corrosion or wearing of the sliding contact, especially if it is kept in one position.

A rheostat is essentially a potentiometer, but is usually much larger, designed to handle much higher voltage and current. Typically these are constructed as a resistive wire wrapped to form a toroid coil (or most of one) with the wiper moving over the upper surface of the toroid, sliding from one turn of the wire to the next. Sometimes a rheostat is made from resistance wire wound on a heat resisting cylinder with the slider made from a number of metal fingers that grip lightly onto a small portion of the turns of resistance wire. The 'fingers' can be moved along the coil of resistance wire by a sliding knob thus changing the 'tapping' point.

Potentiometers are relatively inefficient as power controllers as they simply convert unused power into heat. An electronic speed controller is much more efficient and is the preferred method of power control where power conservation is important.