Potentiometer

Potentiometer – Working, Circuit Diagram, Construction & Types Resistor, a small bundle of resistance, is one of the most used basic components in an electric circuit. Mostly used to regulate the current flow by adding/subtracting resistance from the circuit, these resistors are available in many shapes and sizes. These resistors can be broadly classified as fixed and variable resistors. As their respective names suggest, a fixed resistor has a single fixed value of resistance, whereas a variable resistor has resistance value over a defined range.  Out of the numerous linear and Non-linear variable resistors available, the most common is the Potentiometer. This article deals with the working principle, construction and application of a potentiometer. So let’s get started! Potentiometer (pot) The potentiomers or the “pots”, as it is commonly known in the electric circles, is a three terminal variable resistor. Out of its three terminals, two of them are fixed and one  is a varying(linear / rotary) terminal. The value of the resistance can be changed from zero to a defined upper limit, by just manually sliding the contact over a resistive strip.  As the resistance changes, the current through the circuit changes and hence according to the ohms law, the voltage across the resistive material also changes. Since it coverts rotary or linear motion by the operator into a change in resistance(hence a change in electric parameter), it can be called an electro-mechanical transducer. They are passive in nature, therefore dissipate power rather than supplying power to the circuit. In  its early days of manufacture, it was thought of like a large wire wound resistive coil,which could be adjusted so as to measure the voltage difference across it . Hence, the name “potentiometer” was given to this device, which is coined from the combination of two words: potential difference and metering. They have come a long way since then. Gone are the days of large bulky potentiometers, now what we get is quite small and easy to use and light to carry; also they have now used in wide range of applications. Now that we have had an introduction about the potentiometer, you might have a curiosity of knowing how it looks like. Figure 1 shows some practical pots, while figure 2 shows the standard symbol of the same.     It is represented by a zigzag line with an arrow pointing inwards at the center. Next lets discuss the very crux of this article, the working principle of the potentiometer. How does it work? As already discussed, a potentiometer has three terminals. When connected to a circuit, the two fixed terminals are connected to the ends of the resistive elements while the third terminal is connected to the wiper. In the circuit diagram shown  below,  the terminals of the potentiometer are marked 1, 2 and 3. The voltage supply is connected across terminals 1 and 3, positive lead to terminal one while negative lead to terminal three.  The terminal 2 is connected to the  wiper.   Now a closer look into the figure, we can see that at the current position of wiper, there are two resistive paths just like the resistor is split into two resistors. Out of these two resistors, the one having longer resistive path will have a higher resistance. This is due to the fact that resistance of a resistor depends on its length (since R=ρ). Higher the length, higher is the resistance, provided the material of the resistor and its cross-sectional area remains same. For simplicity, lets name the two resistors, R1 and R2 (Refer figure). The wiper voltage is actually the voltage...
read more

The post Potentiometer appeared first on Electronic Circuits and Diagram-Electronics Projects and Design.