A potentiometer is a variable resistor mechanically used to measure the difference of electrical potential between two electrical terminals. The potential difference is what is commonly known as voltage.
The first potentiometers and simpler are the rheostats.
The potentiometer is a device that limits the passage of electrical current, causing a voltage fall. The fact that the voltage can vary makes it possible to control different devices, since the operation of the devices can be regulated by the amount of voltage given by the potentiometer.
The potentiometer consists of two resistors in series. The value of these resistances can be modified by the user.
What is a potentiometer used for?
It is usually used in a technical field.
The potentiometer serves to limit the passage of electric current, therefore, it refers to the current, causing a voltage fall. The value of the current and voltage for the potentiometer can be varied only after modifying the value of its resistance. Bear in mind that if it were a fixed resistance, the value of the resistance would always be the same.
Parts of a potentiometer
- Fixed part: The potentiometer has a fixed part that is responsible for establishing an electrical resistance.
- Moving part: This part is in contact with the fixed part. When it moves it causes the electrical resistance introduced in the terminals of the potentiometer to vary.
Potentiometer how it works?
A potentiometer has a simple operation. It basically consists of a variable resistor, which changes its value as the current increases.
This resistor has three terminals to which the voltage to be measured is connected.
One at each end and a third connection to a slider. This control will allow us to increase or decrease resistance. The value between the connections can be varied by turning the moving part of the potentiometer.
By varying the resistance, the potential difference between the terminals varies. Therefore the value of the voltage is determined by the variation of the resistance.
1. According to its application:
- Volume control potentiometers: They are suitable to be used as a voltage control element in an electronic device. Here the user will activate them to vary the normal operating parameters. For example, the volume of an audio device.
Within the control potentiometers we have:
- Rotary potentiometers. They will be controlled by turning their axis. They are the most used for their long duration and little space they use.
- Sliding potentiometers. It is controlled by running a cursor in a straight line. They are used in graphic equalizers.
- Adjustment or multiple potentiometers. They have coaxial axes. In this way they occupy much less space. They are going to control the tension when presetting it, almost always from the factory. The user does not usually have to touch up, so they are not usually accessible from the outside. There are both encapsulated in plastic and without capsule, and are usually distinguished potentiometers vertical adjustment, whose axis of rotation is vertical, and potentiometers horizontal adjustment, with the axis of rotation parallel to the printed circuit.
2. According to the law of variation of resistance:
- Potentiometers by linear variation. The resistance is directly proportional to the angle of rotation.
- Logarithmic potentiometers. The resistance varies depending on the angle of an inverse exponential form.
- Sine-wave potentiometers. It varies depending on the angle sine. It may have limit stops or not.
- Antilogarithmic potentiometer: varies exponentially at the angle of rotation.
3. Digital potentiometer
They are those that work when simulating an analog potentiometer, but with the difference that it uses an integrated circuit, characterized by its greater precision.
There are two types of manufacturing of a potentiometer:
- Printed: Made with a carbon or cermet track on a hard support such as bakelised paper (cardboard prespan), fiberglass, bakelite, etc. The track has two contacts at its ends and a cursor connected to a skate that slides on the resistive track.
- Windings: Consists of a toroidal winding of a resistive wire (for example, constantán) with a cursor that moves a skate on it.
Applications of potentiometers
Potentiometers are used for many electrical and electronic devices to establish the output level. They can be applied both to perform a command action, that is, to modify any condition, as well as an adjustment function, that is, detect any irregularity and correct it.
- Speed regulators in motors: If we put a potentiometer with a motor in series by increasing the resistance of the potentiometer, the motor speed D.C. will decrease. This is best done with the TRONIC series potentiometers. The potentiometer control voltage.
- Audio control: We can use a potentiometer to control the volume of a stereo, the volume in hearing aids, radios or amplifiers. Logarithmic potentiometers are almost always used for audio due to their asymmetric behavior if a variation of the axis occurs. They are common in the volume of a radio.
- Lighting: We can use a potentiometer to control the lighting level of a television, or the brightness of a computer screen.
- Control systems: They are common in control systems if you want to act as a meter of a particular variable. For example: the level of heat in a radiator or to indicate the level of gasoline in a car.