A potentiometer is a common component in
electronic devices, which is widely used in various circuit control systems. It
controls the voltage by adjusting the resistance in the circuit.
In this article, let’s discuss in detail
what a potentiometer is, its working principle and application, and its difference
with a rheostat.
1. What is a potentiometer?
First, what is a potentiometer? A
potentiometer is a common electronic component, often called a "pot",
used to precisely control voltage or current in a circuit.
The core part of a potentiometer is a
variable resistor, which is usually equipped with three terminals: two fixed
terminals and an adjustable sliding terminal (also called a wiper). By rotating
the control shaft of the potentiometer, people can adjust the position of the
wiper between the two fixed terminals, thus flexibly changing the resistance
value. This design makes the potentiometer ideal for use in situations
requiring precise adjustment.
The Potentiometer Diagram/
Symbol
In a circuit diagram, the symbol for a
potentiometer is usually represented as a resistor with an arrow. This symbol
consists of two parts: a rectangular or jagged line representing a fixed
resistance element, and a diagonal arrow that intersects the resistance
element. The two terminals of the resistance element are connected with two
fixed terminals, representing the poles of the potentiometer, and the arrow
points to a certain position of the resistance element, indicating the sliding
contact of the potentiometer.
The Potentiometer Formula
The operation of a potentiometer can be
described using the voltage divider formula. When the total resistance of the
potentiometer is R, the wiper divides this resistance into two parts: R ₁ and R ₂
. These two resistances add up to the total resistance, so R ₁ + R ₂=R.
The input voltage Vin is applied across the two ends of the potentiometer, and
the position of the wiper determines the values of R ₁
and R ₂, which, in turn, affects the output
voltage Vout.
The output voltage at the wiper, Vout ,
can be calculated using the following voltage divider formula:
This potentiometer formula can help us calculate
the potential difference at any given point along the resistive element.
Types of Potentiometers
With the development of technology,
electronic devices have higher and higher requirements for components.
Therefore, people have designed various types of potentiometers according to
different needs.
The following are several common potentiometer
types: rotary potentiometer,
linear potentiometer and digital potentiometer.
|
Type
of Potentiometer
|
Rotary
Potentiometer
|
Linear
Potentiometer
|
Digital
Potentiometer
|
|
Adjustment
Method
|
Adjusts
resistance by rotating a shaft, typically between 270° to 300°, some can rotate 360° or multi-turn for
precise adjustments.
|
Adjusts
resistance by sliding the wiper along a straight path, changing the
resistance proportionally along the resistive element.
|
Adjusts
resistance through digital signals (via protocols like SPI or I²C) using a
microcontroller or digital circuit.
|
|
Structure
|
Three
terminals: two fixed terminals connected to the ends of the resistive
element, and a wiper that rotates along the element.
|
Three
terminals: two fixed terminals connected to the ends of the resistive
element, and a sliding wiper that moves along a linear path.
|
An
internal resistive network with electronically controlled switches. No moving
parts, controlled digitally.
|
|
Applications
|
Commonly
used in volume controls, brightness adjustments, and frequency tuning.
|
Used
in audio mixing consoles, electronic instruments, and lighting controls for
smooth linear adjustments.
|
Used
in applications requiring automated control such as audio adjustment,
automatic gain control, and remote-controlled systems.
|
|
Advantages
|
Simple
manual adjustment, easy to use for general applications.
|
Smooth,
linear adjustment; intuitive for manual control in devices requiring linear
changes.
|
No
mechanical wear, highly precise, programmable, and easy integration with
digital systems.
|
|
Disadvantages
|
Mechanical
wear can occur over time with repeated use.
|
Limited
travel distance and potential wear from frequent use.
|
Limited
resolution, requires external power and control signals, more complex to
integrate.
|
2. How does a potentiometer
work?
How does a potentiometer work? It’s very
easy. It adjusts the output voltage or resistance value by changing the
position of the sliding contact on the resistance element.
When the slide moves along the resistance
element, the potentiometer changes the resistance of the two parts of the
circuit, thus changing the output voltage. By adjusting the position of the
slide, the resistance ratio of the two parts can be adjusted, which directly
affects the output voltage.
As we can see from the potentiometer
diagram above, the movement of the slide splits the total resistance into two
parts, enabling it to function as a voltage divider or variable resistor.
For example, in the volume control knob,
rotating the potentiometer can adjust the resistance to change the volume. In a
tuning circuit, a potentiometer adjusts the tuning frequency of a radio
receiver by changing the voltage in certain sections.
3.
Potentiometer vs rheostat
What is rheostat?
From the above, we learned that the
potentiometer has three terminals and can also be used as a voltage divider.
Unlike a potentiometer, a rheostat is a two-end device that adjusts the current
in the circuit by changing the resistance value.
What's the difference
between a potentiometer and a rheostat
A potentiometer and a rheostat are mainly
different in use. The potentiometer is mainly used to control voltage, while
the rheostat is used to control current.
At the same time, the potentiometer can
also be used as a variable voltage divider, and the rheostat can be used as a
resistor to adjust the current flow.
Structurally, the slide of a
potentiometer divides the resistance element into two parts, while in a
rheostat, the slide controls the circuit only by adjusting the total
resistance.
Conclusion
All in all, a
potentiometer is a crucial component in electronic circuits.
It offers precise
control over voltage by adjusting resistance. Its basic working principle,
symbol, and formula show us how it
can divide voltage or act as a variable resistor. With various types available,
potentiometers are widely used in applications such as audio control, light
dimming, and tuning circuits. When comparing potentiometers vs rheostats, the
primary difference is that potentiometers control voltage, while rheostats
control current. Understanding these differences is essential for selecting the
right component for your circuit.
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