Many of the devices that we use daily contain a potentiometer. For example, you can find a potentiometer in audio equipment; it’s used for volume control. A potentiometer is usually constructed of 2, 3, or 6 legs (pins). But why does a potentiometer have 2, 3, and 6 legs?
Why Does a Potentiometer Have 2, 3 & 6 Legs?
Why Does a Potentiometer Have 2 Legs?
The potentiometer’s two pins are one of the terminal pins, and the other is the middle pin (the slider). The terminal pins are connected to the resistive element. And the middle pin (the slider) is in between the terminal pins; it can rotate over or slide along the element.
Why Does a Potentiometer Have 3 Legs?
The three-pin potentiometer is similar to the two-pinned potentiometer. The three-pinned potentiometer is constructed of two-terminal pins and a middle pin (the slider). The terminal pins connected to the resistive element and the slider can slide or rotate depending on the potentiometer type.
Why Does a Potentiometer Have 6 Legs?
The six-pin potentiometer is a dual-potentiometer, which means it’s constructed of two three-pinned potentiometers connected and controlled by a common shaft. You can use any of the potentiometers without using the other, but there must be no connection between the two potentiometers.
How Do You Use a Potentiometer With 2, 3 & 6 Legs?
How Do You Use a 2 Leg Potentiometer?
The two-pin potentiometer can be used as a rheostat. You can use any one of the terminal pins for input. Then, use the middle pin (the slider) for output. The slider controls the amount of resistance the potentiometer puts to the electric circuit.
For example, If the potentiometer is 30kΩ, it means that the potentiometer, when is used as a rheostat, has a maximum resistance of 30kΩ and a minimum resistance of 0kΩ. So when you use the slider, the value of resistance is between 30kΩ and 0kΩ.
How Do You Use a 3 Leg Potentiometer?
The three-pin potentiometer is used as a voltage divider. First, Connect one of the terminal pins to the GND. GND is the ground; it’s connected to the power supply’s negative terminal. It can be connected to any terminal pin, while the other is connected to VCC.
The VCC is the Voltage Common Collector; it’s the device power input. The VCC is connected to the positive terminal of the power supply. So you can connect one of the terminals as the VCC and the other as the GND; the order doesn’t matter as long as each one is connected to the right terminal.
The middle pin (the slider) determines the output voltage, so you can control how small you want the output voltage by moving the slider. And you can calculate the output voltage using a simple equation from Ohm’s Law: Vout = Vcc * R2 / R1 + R2.
How Do You Use a 6 Leg Potentiometer?
A six-pin potentiometer is used the same way the three-pinned potentiometer, but you have four terminals pins and two sliders instead of two terminals pins and one slider. So you can connect one potentiometer to a certain circuit and the other potentiometer to another circuit.
What Are the Types of the Potentiometer?
The potentiometers have four main types:
The Linear Potentiometer
The most common type of potentiometer is the linear taper. Taper is a concept in potentiometers, where the taper means a relationship between the potentiometer’s resistance and the slider’s position. In the linear potentiometer, the relation is linear.
The linear relationship means that when the slider of the potentiometer is in the middle, the potentiometer only imposes half of its maximum output voltage. And by moving the slider forward or backward, the voltage output increase and decreases. And this type has a B letter followed by its maximum resistance.
The Logarithmic Potentiometer
It’s mainly used in Audio equipment. The logarithmic tapers don’t change the output linearly as the linear taper; they change it logarithmically. The logarithmic change is more suitable for audio devices because the linear taper changes the volume with great values.
The second disadvantage of the linear taper is its limited change. The linear taper doesn’t provide any considerable change after 60 degrees. And all of that makes the linear tapers aren’t good for the audio equipment. The logarithmic tapers are more suitable than the linear ones.
The logarithmic tapers change the output logarithmically, which means you can gradually increase or decrease the volume. They are similar to the inverse logarithmic tapers, but they are very difficult to obtain because they can only be found in pro-audio equipment.
An inverse logarithmic taper can be known by the letter C found on its board, followed by its maximum resistance. Meanwhile, the logarithmic taper has an A letter on its board, followed by its maximum resistance.
The Digital Potentiometer
It has the same functions as the normal potentiometer. However, the digital potentiometer uses digital signals and switches instead of mechanical action. It consists of several resistors connected in series; a key follows each resistor. The key plays the role of the slider in the normal potentiometer.
The number of resistors determines the maximum output that can be obtained. Any key can be closed, but only one key can be closed simultaneously. The digital potentiometer is used in the same applications as the normal one, but the digital can have many other uses other than volume control.
The Membrane Potentiometer
It’s consist of three layers:
- A resistive path is printed onto a membrane base.
- A collector with a printed short-circuit path.
- A circumferential spacer.
The third layer protects the membrane against moisture and dust and separates between the first and the second layer. The potentiometer starts to work when any pressure is applied to the surface. The pressure can be applied by a finger or a magnet; then, the first and second layers connect and send precise signals.
How To Choose a Suitable Potentiometer?
You can determine the suitable potentiometer by following very simple steps:
- Pick the right type and shape for the circuit.
You can choose between a rotary, slide switch, or dial.
- Make sure the size of the potentiometer will fit in the circuit.
You may need to reach out in the future to make adjustments.
- Ohm’s Law.
You will need to understand Ohm’s Law to determine the resistance of the circuit.
- Know the potentiometer range.
Since you used Ohm’s Law to determine the resistance of the circuit, you will now know which potentiometer range you need.
How To Know if the Potentiometer Is Bad?
First, you need to get a device to test the potentiometer. For example, you can get a lamp. Then, connect the lamp to the potentiometer using the two-pinned method. Afterward, start increasing and decreasing the slider if the lamp brightness increases and decreases. Then, the potentiometer is working fine.
What Can Go Wrong With the Potentiometer?
The potentiometer can face two problems in general:
1. The Damage of The Carbon Film
This can be caused due to scratching of the carbon film. First, you can remove the cover of the potentiometer and clean the carbon film with absolute alcohol. Then try to adjust the pressure of the sliding part to make sure of the good contact for more precise output.
2. Potentiometer Structural Damage
If the customs are always open or the switch part is off, you can fix this by replacing the box with a new one. In case of a poor connection or it stops working, you can apply oxidizing to fix the connection issue or replace the string with a new string.
And here’s a video about fixing potentiometer:
What Are the Applications of a Potentiometer?
You can find a potentiometer in many different applications; it’s not used only in audio equipment. For example:
- Voltage divider in electronic circuits.
- Medical equipment.
- Machines of wood processing.
- Machines of mold injection.
- Controllers: volume control, tone control, linearity control.
What Is the Difference Between a Rheostat and a Potentiometer?
A rheostat applies to Ohm’s Law, which means that the current increase as the resistance it’s facing is decreased, and it decreases as the resistance it’s opposing decreases. And the rheostat is made of different materials, carbon disk, metal ribbons, and fluids. It’s not polarized, so it can operate in reverse.
A potentiometer is made of a resistive element as graphite or cermet. The resistive element takes the shape of an arc, and the slider slides over it. And it can operate in reverse as the rheostat. The potentiometer has many types linear taper, logarithmic taper, linear slider, and digital potentiometer.
What Is the Difference Between a Voltmeter and a Potentiometer?
There is no big difference between voltmeter and potentiometer, both of them measure voltage. However, there’s a difference in which voltage each measure:
It measures the potential between two points in the electric circuit, which means that it measures the end terminal voltage of the circuit.
It uses a known voltage source to measure unknown voltage, which means it measures the electromotive force of the circuit.
To sum up, a potentiometer differs from a rheostat or a voltmeter. The potentiometer has many different types; each type is better at a different task. You can use it in different ways two-pinned, three-pinned, or six-pinned. And that is what makes a potentiometer so essential to any electronic device.
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