Contents
What is a Potentiometer?
[Image: Potentiometer Pinout]
The potentiometer is also known as a variable resistor. It is a resistor that allows you to control the flow of electricity with the help of its contact and its terminals.
A potentiometer has three terminals and movable contact with manually adjustable voltage.
For every potentiometer, there is an electronic and mechanical control that helps alter the resistance to the flow of electricity.
However, due to the altered resistance, the current and voltage running through and across the potentiometer get regulated by Ohm’s Law.
How Does a Potentiometer Work?
[Image: Potentiometer]
A potentiometer works like a voltage divider. Applying voltage to the resistive element’s end terminals (R1, R2) produces electrical potential from one element point to the other. The wiper then leverages the element, generating output voltage.
Its output voltage depends on the wiper’s position (wiper to end terminal). Voltage levels can start at 0 (ground) and adjust to the full input voltage. If the wiper is moving toward one terminal end, the output voltage decreases. This happens when R1 shrinks while R2 increases.
On the other hand, the output voltage increases as the wiper moves to the opposite end. In this case, R1 grows while R2 decreases.
Key Features of Potentiometers
Below are some of the characteristics:
Taper
This is one of the major features of a potentiometer. It helps you to effectively use it, and choose the ideal application or the right device.
This feature is better known as the taper of pots or laws of pots, and it is simply the ratio between the resistance and the wiper position. As an engineer, you may find that this ratio takes a linear, logarithmic, or antilogarithmic format when plotted as a graph.
Linear
The linear taper type changes the resistance based on the wiper’s position, resulting in equal adjustments. Its resistance consistently rises or falls due to the wiper’s motion.
Linear is suitable for applications requiring precise control. Some use cases of this potentiometer include joysticks, oscilloscopes, robots, LED controllers, light systems, and more.
Logarithmic
A logarithmic taper potentiometer makes small resistance changes if the wiper moves slightly at the low resistance end.
Gradual resistance changes occur when the wiper extends along the track toward the high-resistance end.
The logarithmic taper potentiometer is for audio signal adjustments. Common applications include hearing aids, headsets, amplifiers, record studios, audio equipment, audio devices, etc..
Marking Codes
This is to indicate the maximum resistance that a potentiometer can attain. It helps engineers make an informed decision when choosing a potentiometer.
Therefore, manufacturers usually input marking codes for pots. Thus, a pot marked with 100K can only attain a resistance of 100K ohms.
Besides, a marking code also functions as an indicator for a pot’s taper. However, in this case, the marking codes are different and mean different things, depending on the region of the user.
Resolution
It simply refers to the minimum amount of resistance that you can vary in a pot. For instance, if you see a pot with a resistance of 50k ohms and a resolution of 10, this means that the minimum variation in the resistance is 10 ohms.
Furthermore, this means that the smallest variation in resistance will be in multiples of ten—for example, 10 ohms, 20 ohms, 30 ohms, and so on.
Hop On Hop Off, Resistance
Firstly, it deals with the behavior of the wiper in the potentiometer. In a pot, you will find the resistive material in between two terminals, made of metals with low resistance.
As a result of the low resistance, there is usually a sudden change in resistance whenever the wiper enters or leaves the region between the two terminals. This action of the wiper is what technicians refer to as hop on, hop off resistance.
What Are the Types of Potentiometers?
Here, we will focus on potentiometers based on their modus operandi. Under this category, there are three POT types: the Rotary Potentiometer, Digital Potentiometer, and Linear Potentiometer.
Rotary Potentiometer
Rotary potentiometer.
Do you remember the knob used to control the volume on a stereo player? By turning the knob in either direction, you can either increase or decrease the volume of the stereo. This is exactly how the rotary potentiometer works.
The POT delivers adjustable supply voltage to electronic and electrical circuits by converting its circular movement into variable resistance.
In this type of potentiometer, you will find two contacts placed in a half-circle with uniform resistance. The third terminal is a wiper, and it links to the rotating knob.
When you move the knob, the wiper also moves across the resistance, and this alters the resistance of the potentiometer.
There are many types of Rotary potentiometers. They include the Single-turn Pot, Dual Gang Pot, Multi-turn Pot, Servo Pot, and Pots using Concentric shafts.
Rotary potentiometers have applications for volume control, calibration, motor speed control, tone control, light dimmers, position sensors, and more.
Linear Potentiometer
Linear potentiometer.
The linear POT works exactly the same way as the rotary POT does, except that it uses linear motion instead of a rotary motion to deliver varying resistance.
However, linear POTs find the best use when used to measure the internal resistance of a battery cell or compare a standard cell with a battery cell.
The linear potentiometer consists of a slider mechanism, track, and wiper. In this case, the slider refers to the external component for resistance adjustments. While the track is the resistive element, the wiper is the contact connecting to the slider.
Moving the slider mechanism along the straight track causes the wiper to move across the resistive element. This enables the control of the resistance.
There are different types, such as the linear slider potentiometer, Multi-turn slide, dual slide, and motorized fader.
Linear potentiometers have applications across various industries. They include industrial and robotics (position sensing), medical devices, audio equipment (volume and tone control), and consumer electronics.
It also has other uses like measurement and calibration, HVAC systems, level sensing (tanks), and more.
How to Select the Right Potentiometer?
Consider these factors when choosing a potentiometer for your project.
- Resistance value and range: One of the features of a potentiometer is its variable voltage and ability to hold up multiple resistance values. To reduce the complexity of the circuit, manufacturers reduce the resistance value of the POT into multiples of 10, 20, 22, 25, 47, and 50. As a result, some popular potentiometer values are 10k ohms, 1k ohms, 5k ohms, and 100k ohms.
- Power rating: This is the amount of power the potentiometer withstands before damage or failure occurs. Typically, standard potentiometers have a power rating between 0.25W – 1W. Large industrial-based potentiometers have a rating of 2W – 10W (higher-power types surpass 10W). The trimmers are 0.1W or lower.
- Taper
- Resolution
- Tolerance: Tolerance is a percentage that indicates how much the nominal resistance differs from the actual resistance. A precision potentiometer has a tolerance as low as ±0.5%, ±1%, ±2%, or ±5%. Meanwhile, the standard type is ±5%, ±10%, or ±20%.
- Mechanical life: A potentiometer can have different life cycles, depending on its type. For example, long-lasting potentiometers have one million to twenty million life cycles. The standard ones have 10,000 – 100,000 life cycles, while trimmers only have thousands.
Applications of Potentiometers
[Image: Potentiometers for audio control.]
A potentiometer has numerous applications in an electric circuit and also in machinery.
- Firstly, the potentiometer allows you to measure the electromotive force or resistance in a cell.
- Also, it functions as an adjustable voltage divider in an electronic circuit.
- Besides there is also an audio application for a potentiometer in a TV or Radio receiver as a medium for volume control, absolute linearity control, or tone control.
- Potentiometers are for angle measurements (robotics), steering angle sensors, fluid level detection (tanks), and linear actuators’ position feedback.
- Finally, there are also power applications for potentiometers, especially with machinery.
Conclusion
Potentiometers have several advantages for the user and their projects. For example, they’re low-cost, versatile, lightweight, and withstand harsh environments. All those qualities make them an easy choice for circuit integration.
This article is a complete guide to the workings of potentiometers. For more questions and inquiries, please contact us.
