Home  Potentiometer

Jan 31 2019

The Differences Between Potentiometer and Adjustable Resistor

Warm hints: This article contains about 4000 words and reading time is about 18 mins.

Introduction

Potentiometers are one of the most commonly used tunable electronic components. The potentiometer is derived from the development of a variable resistor. It consists of a resistor body and a rotating or sliding system. The contact brush of the boom slides on the resistor body to continuously change the resistance between the boom and the two ends. value. The potentiometer is a resistance element having three terminals and the resistance value can be adjusted according to a certain variation rule. Potentiometers usually consist of a resistor and a movable brush. When the brush moves along the resistor body, a resistance value or voltage which is in a certain relationship with the displacement amount is obtained at the output end. The potentiometer can be used as a three-terminal component or as a two-terminal component. The latter can be regarded as a variable resistor, and since it functions in the circuit to obtain an output voltage which is related to the input voltage (applied voltage), so it is called a potentiometer.

Article Core

Potentiometer

Purpose

Introduce what the difference between potentiometer and adjustable resistor.

Application

Semiconductor industry.

Keywords

Potentiometer

Catalog

Introduction


 

Part I Potentiometer

Potentiometer Definition

The Role of the Potentiometer

Understanding of Potentiometers

Type of Potentiometer

Connection of Potentiometer Pins

 

Part II Adjustable Resistor

Definition of Adjustable Resistance

How Is the Adjustable Resistance Connected?

How to Connect Three Pins of Adjustable Resistance?

Part III The Difference Between Potentiometer and Adjustable Resistor



Part I Potentiometer

Potentiometer Definition

A potentiometer is a type of variable resistor. Usually consists of a six-leg potentiometer resistor body and a rotating or sliding system, that is, a moving contact moves on the resistor body to obtain a partial voltage output.

How to use potentiometer as variable resistor and voltage divider


The Role of the Potentiometer

(1) Adjusting the voltage (including DC voltage and signal voltage) and the magnitude of the current.

A potentiometer is an adjustable electronic component. It consists of a resistor body and a rotating or sliding system. When a voltage is applied between the two fixed contacts of the resistor body, the position of the contact on the resistor body is changed by a rotating or sliding system, and a position of the movable contact is obtained between the movable contact and the fixed contact. A voltage that has a certain relationship. It is mostly used as a voltage divider, when the potentiometer is a four-terminal component. Potentiometers are basically sliding varistor, there are several styles, generally used in speaker volume switch and laser head power size adjustment, potentiometer is an adjustable electronic component.

(2) Dividing voltage of variable resistors.

On the exposed resistor body, one or two movable metal contacts are pressed. The contact position determines the resistance between either end of the resistor body and the contact. According to the material line winding, carbon film, solid core potentiometer; according to the relationship between the output and input voltage ratio and the rotation angle, the linear potentiometer (linear relationship), the function potentiometer (in a curve relationship). The main parameters are resistance, tolerance, and rated power. It is widely used in electronic equipment for volume control in audio and receivers.


Understanding of Potentiometers

There are many types of potentiometers. The more common ones are: ordinary rotary potentiometers, potentiometers with switches, ultra-small potentiometers with switches, straight-slip potentiometers, multi-turn potentiometers, trimmer potentiometers, dual potentiometers, etc. The word symbol of the potentiometer is “Rp”, and the symbols commonly used in the circuit diagram are as shown below.

potentiometers

A potentiometer is a type of variable resistor. Usually consists of a six-leg potentiometer resistor body and a rotating or sliding system, that is, a moving contact moves on the resistor body to obtain a partial voltage output.

The role of the potentiometer - adjust the voltage (including DC voltage and signal voltage) and the magnitude of the current.

The structural characteristics of the potentiometer - the resistor body of the potentiometer has two fixed ends. By manually adjusting the rotating shaft or the sliding handle, changing the position of the moving contact on the resistor body changes the moving contact between any fixed end and the fixed end. The resistance value, which changes the magnitude of the voltage and current.

 potentiometer

A potentiometer is an adjustable electronic component. It consists of a resistor body and a rotating or sliding system. When a voltage is applied between the two fixed contacts of the resistor body, the position of the contact on the resistor body is changed by a rotating or sliding system, and a position of the movable contact is obtained between the movable contact and the fixed contact. A voltage that has a certain relationship. It is mostly used as a voltage divider, when the potentiometer is a four-terminal component. Potentiometers are basically sliding varistor, there are several styles, generally used in speaker volume switch and laser head power size adjustment, potentiometer is an adjustable electronic component.

Variable resistor for voltage division. On the exposed resistor body, one or two movable metal contacts are pressed. The contact position determines the resistance between either end of the resistor body and the contact. According to the material line winding, carbon film, solid core potentiometer; according to the relationship between the output and input voltage ratio and the rotation angle, the linear potentiometer (linear relationship), the function potentiometer (in a curve relationship). The main parameters are resistance, tolerance, and rated power. It is widely used in electronic equipment for volume control in audio and receivers.

In addition to the nominal resistance and rated power, the main parameters of the potentiometer also have a resistance change characteristic, which refers to the relationship between the resistance value and the rotation angle or sliding stroke of the boom. Common potentiometer resistance changes are linear (X-type), exponential (Z-type), and logarithmic (D-type). The curves of the three types of potentiometer resistance as a function of the angle of rotation of the movable contact are shown in the figure. In the figure, the ordinate indicates the actual value of the resistance at a certain angle and the percentage of the total resistance of the potentiometer. The abscissa is the percentage of the rotation angle and the maximum rotation angle.

The resistance change of the X-type potentiometer is linear with the rotation angle. That is, the distribution of the conductive substances on the resistor body is uniform, so the resistance per unit length is equal. It is suitable for applications requiring uniform adjustment, such as voltage dividers, bias current adjustment and other circuits. When the Z-type potentiometer starts to rotate, the resistance value changes little, and when the rotation angle approaches one end of the maximum rotation angle, the resistance value changes more obviously. Because the human ear has a slight increase in the tiny sound, it feels very sensitive, but after the sound reaches a certain value, even if the sound power is greatly increased, the feeling of the human ear does not change much. This potentiometer is suitable for The volume control circuit, because the potentiometer is used for volume control, the relationship between the volume and the potentiometer rotation angle is approximately linear. The resistance change of the D-type potentiometer is opposite to that of the Z-type. The resistance value changes greatly when it starts to rotate, and the resistance value changes slowly when the rotation angle approaches the maximum value. The D-type potentiometer is suitable for circuits such as tone control.

Resistance Change Characteristic Curve

Resistance Change Characteristic Curve

If the potentiometer has slight contact failure, the carbon film and the contact of the moving piece can be cleaned with pure alcohol; if the carbon film is worn seriously in the potentiometer and the contact is bad, the metal play contact can be gently bent inward or outward. Change the trajectory of the metal brush on the carbon film; if the potentiometer has an open circuit between the film and the carbon film (mostly open at the silver coating), and another fixed piece is not used or welded together with the moving piece, then The welding position of the two fixed pieces can be exchanged and can still be used normally. For example, the potentiometer A stator and the carbon film are broken, at this time, the potentiometer A can be soldered and the B-slice can be replaced. If the carbon film is worn, use a pencil to apply the carbon on it to maintain its use. If it is severely damaged or the conditions permit, it will be replaced as much as possible.


Type of Potentiometer

(1) Synthetic carbon film potentiometer: It is the most used potentiometer at present. The resistor body is made of a mixture of carbon black, graphite, quartz powder, organic binder, etc., and is coated on a rubber board or a fiberglass board.

Advantages: high resolution and wide resistance range;

Disadvantages: large sliding noise, poor heat and humidity resistance.

Variety: Common synthetic carbon film potentiometer, small synthetic carbon film potentiometer with switch, single-band switch (no switch) potentiometer, double coaxial no switch (with switch) potentiometer, double-axis independent switch ( With switch) potentiometer, small precision synthetic carbon film potentiometer, push-pull switch synthetic carbon film potentiometer, straight-slip synthetic carbon film potentiometer, precision multi-turn synthetic carbon film potentiometer.

(2) Wirewound potentiometer: The resistor body is made of a wire wound around a metal or non-metal plate coated with an insulating material.

Advantages: high power, low noise, high precision and good stability;

Disadvantages: Poor high frequency characteristics.

(3) Metal film potentiometer: The resistor body is formed by depositing a metal alloy film, a metal oxide film, a metal composite film, and a ruthenium oxide film material on a ceramic substrate by a vacuum technique.

Advantages: high resolution, sliding noise is smaller than synthetic carbon film potentiometer;

Disadvantages: small resistance range and poor wear resistance.

(4) Straight-slip potentiometer: The resistor body is a rectangular strip, which changes the resistance value by linear movement of the slider connected to the slider.

Uses: Generally used for volume control or equalization control in TV sets and stereos.

(5) Single-turn potentiometer and multi-turn potentiometer.

Single-turn potentiometer: its sliding arm can only rotate within less than 360 degrees, generally used for volume control;

Multi-turn potentiometer: For every revolution of its rotating shaft, the sliding arm contact only changes a small distance on the resistor body. When the sliding arm is from one extreme position to the other extreme position, the rotating shaft needs to rotate a plurality of turns. Generally used in precision adjustment circuits.

(6) Solid potentiometer: It is made by mixing and heating materials made of carbon black, graphite, quartz powder, organic binder, etc., and then pressing on a plastic substrate and then heating and polymerizing.

Advantages: high resolution, good wear resistance, wide resistance range, high reliability and small volume;

Disadvantages: high noise and poor high temperature resistance. Variety: can be divided into small solid potentiometer, linear solid potentiometer, logarithmic solid potentiometer.

(7) Single potentiometer and double potentiometer.

Single potentiometer: a set of potentiometers controlled by a separate shaft;

Double potentiometer: Usually two potentiometers with the same specifications are mounted on the same shaft. When the shaft is adjusted, the sliding contacts of the two potentiometers rotate synchronously, which is suitable for the volume adjustment of the two-channel stereo amplifier circuit. There are also some double-connected potentiometers that are asynchronous.

(8) Step potentiometer: It consists of stepper motor, shaft resistor body and moving contact. The moving contact can be manually adjusted by the rotating shaft or by a stepping motor.

Uses: Used for volume control in audio power amplifiers.

(9) With switch potentiometer: A switch device is attached to the potentiometer. The switch is coaxial with the potentiometer, and the movement and control mode of the switch are divided into two types: rotary type and push-pull type.

Uses: Used for volume control and power switch in black and white TV sets. The small rotary type with potentiometer is mainly used for volume control (or current, voltage regulation) and power switch in semiconductor radio or other small electronic products.

Type: The number of switch positions is single pole single throw, single pole double throw and double pole single throw.

(10) SMD type potentiometer: It’s also knew as chip potentiometer, it is an ultra-small linear potentiometer without manual rotating shaft. It needs to use tools such as screw driver when adjusting.

Type: divided into single-turn potentiometer and multi-turn potentiometer - is a precision potentiometer, there are two structures of vertical and horizontal.


Connection of Potentiometer Pins

The potentiometer has 3 feet, 1 pin is grounded, 2 pins are connected to the output, and 3 pins are connected to the signal input. 1 foot 3 feet can be distinguished. The general potentiometer, the middle is the moving piece, so if you measure the resistance, connect the 1st and 3rd feet, measure the total resistance, the moving piece will not move, the resistance will not change; connect 1, 2, the resistance will be from clockwise The direction becomes larger (moving the movement); the 2 and 3 are opposite.

Double potentiometer connection

The 6 feet are called double potentiometers, which means that 2 single units are together.

8-pin potentiometer

The 8-pin potentiometer should have a switch, which is generally used on car audio.

Potentiometer Connection Diagram

Potentiometer Connection Diagram

Three-legged potentiometer connection.

The connection between the left foot and the middle one foot and the right side, the connection function of the middle two feet is the same?

If the motor speed is connected, can you use a three-pin potentiometer and control the motor's forward and reverse? How to pick it up?

The feet on both sides of the potentiometer are their full resistance, the middle foot is the sliding node, the power supply is connected from one foot on both sides, and the voltage is changed from the middle leg.

The speed of the DC motor changes with the applied voltage, so the rotation of the intermediate foot changes the voltage, which changes the speed of the motor.

Changing the positive and negative power of the DC motor can reverse the motor and the potentiometer does not have this function.


Part II Adjustable Resistor

Definition of Adjustable Resistance

The adjustable resistor is also called a variable resistor. The adjustable resistor is a type of resistor. The size of the resistor can be artificially adjusted to meet the needs of the circuit.

Adjustable resistors can be divided into many different types and types according to the size of the resistor, the range of adjustment, the adjustment form, the manufacturing process, the material of manufacture, the size of the volume, etc., which are divided into: adjustable resistors for electronic components, adjustable ceramic disks. Resistor, chip adjustable resistor, wirewound adjustable resistor, etc.

The nominal value of the adjustable resistor is the standard resistance that can be adjusted to the maximum. In theory, the resistance of the adjustable resistor can be adjusted to any value within 0 and the nominal value, but because of the actual structure and design accuracy requirements, etc. The reason is often that it is not easy to achieve 100% "arbitrary" requirements, but only "basically" to adjust within the allowable range to change the resistance.


How Is the Adjustable Resistance Connected?

There are two ways to connect: variable resistance and voltage regulation.

The former is a fixed point connected to 0 bit, and the other fixed point is connected to the voltage, so that the adjustable voltage can be output between the fixed position of the 0 bit and the movable head; the latter is a fixed point and the movable head is shorted, so that the two Between the fixed points becomes a resistor that can be changed.


How to Connect Three Pins of Adjustable Resistance?

The pins on both sides are fixed resistance. The middle of the resistor is the sliding contact, so it can be changed between 0K-nK and can be accessed according to the requirements of the circuit.

The three-legged adjustable resistor is the two ends of the resistor. The middle one is the active connection. The two feet on both sides are the value of the whole resistor. The resistance of the middle leg and either leg depends on the rotation. Depending on the angle. If there is a 50K potentiometer, measure the two feet on both sides, the resistance value is 50K, measure the resistance value of the middle leg and either side of the foot, it depends on the position of the handle, such as the middle position, then the middle foot and any One foot is 25K, and the resistance will change if you continue to rotate. If it becomes smaller, the other side will become larger.


Part III The Difference Between Potentiometer and Adjustable Resistor

The potentiometer is a resistance element whose resistance can be adjusted according to a certain change rule. In fact, the potentiometer is also called an adjustable resistor or a variable resistor in foreign countries, but the domestic adjustable resistor and potentiometer are not an electronic component. There is a difference between them, and the specific text will explain to everyone.

From the structure and the working principle of the adjustable resistor, the potentiometer and the adjustable resistor are basically similar, but they are not all the same, so they also have similarities and differences. What is the difference between the potentiometer and the adjustable resistor? Mainly from the following points to view:

1. Handle: the potentiometer has a handle and the adjustable resistor has no handle.

2. Resistance distribution characteristics: the output characteristics of the potentiometer have various functional characteristics, and the distribution characteristics of the resistors of different potentiometers are different; and the distribution characteristics of the resistors of the adjustable resistors are the same.

3. The number: the potentiometer has a double potentiometer, and the adjustable resistor does not.

4. Volume: the potentiometer has a large volume, a firm structure and a long service life. The adjustable resistor has a small volume and a short service life.

5. Anti-interference performance: potentiometer metal shell grounded in the circuit (the handle is connected to the shell), so the interference is small when adjusting the potentiometer, can achieve the purpose of suppressing interference; and the adjustable resistor has no grounding pin, the adjustment will Disturbed by human body.

6. Installation position and frequency of use: The potentiometer is mounted on the circuit board or on the casing. No matter which installation method is used, his handle needs to extend out of the casing. A convenient adjustment, the machine often adjusts the potential during use. The adjustable resistor is mounted on the circuit board, and is usually not adjusted during use, and the resistance is adjusted only during troubleshooting.

7. Service life: the potentiometer has a firm structure and long service life. However, due to the frequent use of the potentiometer and the mechanical movement, the potentiometer will be damaged in front of the adjustable resistor in the same machine; the adjustable resistor has a simple structure, is improperly damaged, and has a short life, but because The frequency of use is low, so there is no shortcoming of short life.


You May Also Like:

Operating Principle of Potentiometer and Method of Trouble Repair

What Is a Potentiometer and How to Choose the Correct Potentiometer?

The Function and Connection Method of Potentiometer

0 comment

Leave a Reply

Your email address will not be published.

 
 
   
Rating: