What is the function of a variable resistor

What is the function of a variable resistor?

Most volume controls are variable resistors! the control you use to dim the lights in some cases. also the speed dial on small electric motors.

To add to what has been mentioned below, the most common use of variable resistors is to calibrate the circuit parameters. this type is called a predefined pot.

This allows a precise adjustment of the operating conditions, for example with the quiescent current in a discrete audio amplifier, or to allow the user to adapt to unique requirements.

These are generally game-forgetful, as they are not suited to frequent adjustments. To provide one of the many resistance values ​​for any circuit, regardless of the instance.

It is based on the principle of the potentiometer, where the resistance on 2 points equals the distance of the length of the resistance wire.

With a change button or similar connection mechanism at different points on the resistance cable, you can choose a resistance as low as 0 and as high as the resistance value of this resistor.

It becomes advantageous to frequently change the values ​​of the resistors, for example, 555 timing circuits.

By applying a voltage on a potentiometer, or a variable resistor, we obtain a linearly variable current that can be used as analog input for different types of controllers


The first is a radial potentiometer in which one turn of the knob equals 0-2 kohms. For example, connect the potentiometer to a properly configured analog input of a variable speed drive to manually adjust the speed of a three-phase induction motor.

The second is a linear potentiometer (which looks a little like a piston, but it is not) and could be used to provide a controller or position controller at the exact location (along a axis) of certain elements.

There are tons used for variable resistances! here are some examples:

Volume control. This is where I used for the first time variable resistors in the form of a potentiometer.

On an electronic guitar, you can use a potentiometer as a kind of voltage divider in which the input signal is sent to one end of the resistive film, the other end is connected to ground and the wiper goes on the exit.

With the wiper set to the end, the input is a very small input-to-output resistance path. when you move the wiper toward the other end of the resistive film.

The resistance between the input and the output increases and attenuates the signal, which makes it quieter until reaching the other end where the wiper is closest to the end, which means that the output is close to grounding and the volume is near. of. Similarly

In a low-pass or high-pass filter, a variable resistor can be used to change the cutoff frequency of the filter on the fly without changing components. this is done in the same way as the volume control on a passive guitar tone control.

The most common use of variable resistors is probably to fine-tune a voltage divider, or a variable resistance sensor, such as a photo resistor, a thermal resistor, and so on.

In principle, the configuration consists of creating a voltage divider with regular resistance and a variable.

Resistance, the voltage drop on the lower resistance can be used as the reference voltage. In this case, you will want to use a potentiometer to indicate the exact voltage you wish to use as a reference or in the case of a sensor type variable. resistance, you can configure a voltage divider.

Thus, when the voltage drop in the sensor reaches a certain point, a separate circuit is activated to do something else, often using a comparator.

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