A Variable resistor is a resistor that does not have fixed value of electrical resistance, that is the value of electrical resistance can be varied or adjusted..
Variable resistor can be divided into 3 types, they are:
A potentiometer is a 3 terminals variable resistor which has a rotating or a sliding contact. The first and third of the 3 terminals are connected to both ends of a resistive material while the second terminal is connected to a sliding contact which is called a wiper. The wiper moves over the resistive material. The location of the wiper decides the output voltage of the potentiometer. If only two terminals are used, one end and the wiper, then it acts as a rheostat. The potentiometer imperatively acts as a variable voltage divider. The common name of a potentiometer is potmeter or pot .The materials used to construct potentiometers, include metal film, carbon composition, wirewound or cermet.
Types Of Potentiometers
There are many varieties of potentiometers. They can be categorized into 2 types:
- Manually adjustable potentiometer (rotary or linear).
- Digital potentiometer
1)Manually adjustable potentiometer- Manually adjustable potentiometer can be divided into two broad types, which includes:
- Rotary potentiometers
- Linear potentiometers
This is the most common type of potentiometer where the wiper turns along a round path. They are mostly and commonly used in audio system for increasing or decreasing of volume. A rotary potentiometer is divided into 5 types namely:
- Single-turn potentiometer
- Multi-turn potentiometer
- Dual-gang potentiometer
- Concentric potentiometer
- Servo potentiometer
This is a type of Potentiometer where the wiper (slider or fader) moves along a linear path. There are 4 types of linear potentiometers, they are
- Single slide potentiometer
- Dual-slide potentiometer
- Multi-slide potentiometer
- Motorized slider potentiometer
Digital potentiometers are potentiometers which are controlled or by digital signals I and switches instead of by mechanical action. Another name for digital potentiometer is digipot or digital resistor. A digital potentiometer is built from a resistor ladder ( a string of small resistors in series) integrated circuit. A digipot can be used control up/down signals or protocols such as I²C and Serial Peripheral Interface (SPI).
Standard Values of Potentiometers
Most potentiometers have common values such as 1K, 2K,5K,10K, 100K ohm,etc.The most used value for potentiometers is 10K ohm.
General Applications Of Potentiometers
The applications of potentiometers are numerous, it will be difficult to mention all of it here.Below are few applications of it:
- They are used for measurement of distances or angles ( single slide pot).
- They are used in joysticks for machine control.
- They are used in audio system for volume control and balance.
- They are used in calibration and tuning of circuits performance.
Materials Used For Potentiometer
- Carbon composition
- Conductive plastic