Variable resistors: Potentiometers, Varistors and Their Comparison
Variable resistors: Potentiometers, Varistors and Their Comparison
Blog Article
Variable resistors are electronic components capable of controlling current by manually or automatically adjusting their resistance value, and are widely used in various electronic circuits. They are mainly categorized into potentiometers and varistors. Potentiometers are commonly used to adjust voltage, while varistors are mainly used to control current. This blog will give you a detailed overview of the definition, types and applications of variable resistors. Many distributors offer a wide range of components of Variable resistors to cater to diverse application needs, like MC7824CT
Definition and Classification of Variable Resistors
Variable resistors can change their resistance value to control current or voltage. It regulates the flow of current by changing the effective length of the resistive material by moving internal sliding or rotating contacts. There are two main types of variable resistors: potentiometers and varistors. Although they both adjust resistance values, they differ in structure, function and application. A potentiometer is a typical three-terminal variable resistor, while a varistor is a two-terminal variable resistor.
Potentiometer
The potentiometer is used as a three-terminal variable resistor, and its function is mainly to regulate and divide the voltage. It consists of a resistor rail and a movable sliding terminal that changes the output voltage by adjusting the position of the sliding terminal. The two fixed ends of the potentiometer are connected to the ends of the resistor rail, while the sliding terminal can be moved along the resistor rail.
During operation, the input voltage is applied between the two fixed ends of the resistor rail, and when the sliding terminal is moved, it occupies a different position on the resistor rail, and the resistance value of the portion of the resistor rail connected to the sliding terminal changes accordingly. The voltage between the sliding end and one of the fixed ends changes accordingly.
Potentiometer Types
Slide Potentiometers
A sliding potentiometer is a linearly designed potentiometer with a straight line resistor rail, where the resistance value is adjusted by moving the sliding terminal along the rail in a straight line. The sliding terminal changes position by pushing or pulling to adjust voltage or current.
Rotary Potentiometers
Rotary potentiometers consist of a circular resistor rail and rotatable sliding terminals that are operated by rotation to change the position of the contact points, thereby adjusting the resistance value. Rotary potentiometers are usually of a single-turn design and can be rotated up to 360 degrees to achieve the maximum resistance value.
Multi-turn Potentiometers
A multi-turn potentiometer is a type of rotary potentiometer that is usually equipped with mechanical gears to increase the number of rotations, and requires more than one rotation to reach its maximum resistance value.
Digital Potentiometers
Digital potentiometers differ from traditional mechanical potentiometers in that they use electronic circuitry to make resistance adjustments. Digital potentiometers do not require manual operation and are capable of remote or automated control.
Applications of Potentiometers
Potentiometers are used in applications such as volume control, circuit regulation and motor control. Volume control is one of the most common uses of potentiometers. By rotating or sliding the potentiometer, the strength of the audio signal can be adjusted to increase or decrease the volume. This application is common in devices such as home stereos, televisions, and radios.
In circuit regulation, potentiometers are used to change the voltage or current in a circuit. For example, potentiometers are used in laboratories and precision equipment to adjust parameters such as voltage references, current limits, etc. In addition, potentiometers can control the speed of a motor by adjusting its input voltage by adjusting the resistance of the potentiometer. This approach is suitable for fans, DC motor drives, and other devices that require variable speed operation.
Varistors
A varistor is a two-terminal variable resistor that is primarily used to regulate current. Unlike potentiometers, varistors do not have a voltage divider function. Varistors usually consist of a wire-wound resistor filament along which the sliding terminals can be moved smoothly. When the sliding terminal changes position, the resistance in the circuit changes accordingly, which in turn affects the current flow through the varistor.
Types of Varistors
Rotary Varistors
Rotary Varistors utilize a circular resistance rail with sliding terminals attached to a rotating shaft that can be rotated to adjust the resistance value. As it rotates, the sliding terminals move across the rail, changing the effective resistance length and adjusting the current flowing through the varistor.
Slide Varistors
A slide varistor consists of a linear resistor rail and a sliding terminal that moves along the rail to adjust the resistance value. It is similar to a slide potentiometer, but is more robust in power handling and can withstand higher currents.
Applications of Varistors
Varistors are mainly used for current regulation and load control in power equipment. Current regulation is one of the common uses of varistors. For example, in laboratories, varistors are commonly used to adjust the power supply output current. In addition, in devices such as electric heaters and heaters, varistors are used to regulate the operating current, thereby changing the temperature and power of the device.
In terms of load control in electrical equipment, varistors are effective in limiting or increasing the current to control the load. For example, in industrial control systems, varistors can be used to regulate the input current of an electric motor. Also, in power transmission and distribution systems, varistors can be used to protect equipment from overloads.
Comparison of Potentiometers and Varistors
Potentiometers and rheostats are both adjustable resistance components, but they have distinct differences in structure, function, and application.
In terms of structure, a potentiometer typically has a three-terminal design, with two fixed terminals and one adjustable wiper, which is used for voltage division; the wiper position can be adjusted to change the output voltage. A varistor, on the other hand, is a two-terminal device primarily used for current control.
Regarding function and application, potentiometers are commonly used in low-current scenarios, such as volume control and brightness adjustment. In contrast, varistors are often found in high-power applications, such as industrial controls, heaters, and motor control.
Report this page