Potentiometer Definition | Types | its Applications
The basic principle of the potentiometer is that the potential drop across any section of the wire will be directly proportional to the length of the wire, provided the wire is of a uniform cross-sectional area and a uniform current flows through the wire.
Another important form of widely used resistor is the variable resistor or Potentiometers.
Types Of Potentiometers, How To Use. (POT Means potentiometer)
What is a Potentiometer (POT)?
A potentiometer is a variable resistor with three terminals whose voltage is adjustable manually with the help of a movable contact, in order to control the flow of electric current through it.
Every variable resistor will have some kind of mechanical or electronic control to vary its resistance, based on the variation of this resistance the voltage across it and current through it is controlled with respect to Ohms Law.
The most obvious use of the potentiometer which most of us have spotted is volume control in radios and other audio equipment.
Symbol of a Potentiometer:-
Being a close relative of resistors, the symbol of a potentiometer also looks very similar to a resistor.
The Symbol of the potentiometer is given in the below image, it will have a resistor and an arrow pointing towards the resistor, the arrow represents the sliding contact of the POT.
The two ends of the resistor are represented as the terminal 1 & 3 and the wiper end is represented as the terminal 2.
How does Potentiometer work?
A Potentiometer (or) POT is a passive electronic component that has two end terminals with a resistive element and the sliding contact called the wiper acts as the third terminal.
The input voltage is applied across the two end terminals and the output is taken between the first end terminal and the sliding contact.
The output voltage will be taken across any one of the two input terminals and the sliding contact. The POT helps us to use variable voltages in the same device.
Different Types of Potentiometers:-
The Potentiometer or POT is manufactured by using different types of materials like carbon composition, cermet, metal film, and conductive plastic.
The Potentiometers are classified into three types based on their working, as Rotary potentiometer, Linear potentiometer, and Digital potentiometer.
Among these three, the Rotary potentiometer is the most commonly used type of potentiometers.
Rotary Potentiometer:-
The best example of a rotary potentiometer is the volume controller available in your stereo and other music playing devices where the rotating knob is used to control the supply to the speaker. The Rotary potentiometer can deliver adjustable supply voltage to the electrical and electronic circuits. Both the Rotary potentiometer and the linear potentiometer operates as the same but the only difference is that the rotary potentiometer converts rotary motion into varying resistance.
The Rotary POT consists of two terminal contacts (pin 1 and 3) with uniform resistance, it is placed in the shape of a semi-circle and the middle terminal (pin 2) is connected to the resistance through a sliding contact called wiper which is attached with a rotating knob.
The knob is rotated to move the sliding contact across the resistance which in turn varies the resistance of the POT. The output is taken between one of the terminals of the semicircle and the terminal attached to the sliding contact.
There are many types of Rotary Potentiometer. The popular ones can be classified as single-turn pot, Multi-turn pot, Dual-gang pot, Concentric pot and Servo pot each type of rotary POT has its own purpose and applications.
Single Turn POT:-
Single Turn Pot can only be rotated to one position which approximately 270 degrees or ¾ of a full turn. Single Turn Pot is mostly used in applications where a single turn can provide enough control resolution.
Multi-Turn Pot:-
The Multi-turn pots are designed with a wiper that is driven on a spiral or helical form, or by using a worm gear.
Usually, these pots have multiple numbers of rotations like 5,10 or 20 for increased precision.
These pots are mostly used in applications like trim pots on the PCB, that require high precision and resolution.
The most popular manufacturer for the multi-turn potentiometer is Bourns. A bourns multiturn potentiometer along with its symbol is shown below.
Dual-gang pot:-
Dual gang pots are designed by placing two potentiometers together on the same shaft, the single turn pots with equal resistance and taper are mostly preferred for the combination.
Although we can add more than two pots in the gangs, it is not very common to do so. Used in stereo audio volume control and other applications where 2 channels have to be adjusted at the same time.
Concentric pot:-
The name itself reveals its operation, it has two potentiometers that can be adjusted individually by means of concentric shafts.
This allows the user to have two controls on the same unit to vary two different resistance.
These pots are mostly used in car radios where the volume and tone control are placed together.
Servo pot:-
Servo pot has a servo motor attached to the pot, the wiper can be controlled automatically by driving the motor.
This type of pot is used in an application that requires both manual and automatic adjustments, mostly in audio equipment where remote control can turn the volume control knob.
Presets and Trimmers:-
Trimmers or trimpots are a special type of rotary potentiometer that can be fixed once in the circuit and used to make occasional adjustments to the circuit.
The rotary wiper on the POT can be adjusted by using a small bladed screwdriver or a similar plastic tool. They are common materials used as the resistive track is either carbon composition or cement.
They are available both as an open skeleton and also mounted in a closed square package as shown below.
As they are low cost, small in size, and simple to use, they are mostly preferred in non-critical circuit applications that require adjustments, tuning, and calibrations.
The trimpots are available both in a single turn and multi-turn, their common life span ranges from only 100-200 cycles. When the Trimmer used as a variable resistor in a circuit it is called a Preset Potentiometer.
Linear Potentiometer:-
Linear Potentiometer has a similar function as the rotary potentiometer, but instead of the semi-circular resistance, there will be a linear resistor here with a sliding contact.
The two ends of the linear resistor are connected across the source or input voltage, the output is taken between the sliding contact and anyone end of the linear resistor.
The linear pots are commonly used for measuring the voltage across a branch of a circuit, for measuring the internal resistance of a battery cell and also for comparing a battery cell with a standard cell.
Like Rotary Pots, linear pots are also available in different types for different applications. The different types of linear pots include slide pot, dual-slide pot, multi-turn slide, and motorized fader.
Slide Pot:-
The slide pot is a single linear slider potentiometer which is also called the fader. The fader is constructed with conductive plastic. These are mostly used for audio applications and single-channel control or measurement of dista
Dual Slide Pot:-
The Dual Slide Pot consists of a single slider that can be used to control two potentiometers in parallel.
They are often used for stereo control in professional audio and other applications where dual parallel channels are controlled.
