The function and connection method of the hottest

  • Detail

The function and connection of potentiometer

potentiometer is actually a variable resistor. Because its function in the circuit is to obtain the output voltage that is related to the input voltage (applied voltage), it is called potentiometer

circuit graphic symbol

the resistance unit of potentiometer is the same as that of resistor, and the basic unit is also ohm, using symbol ω express. The potentiometer is represented by the letter R or RP (W in the old standard) in the circuit, and figure 1 is its circuit graphic symbol

Figure 1 potentiometer circuit graphic symbols

physical diagram, structural characteristics and application of common potentiometers

common potentiometers are shown in Table 1

meter 1 common potentiometer physical diagram and application

function of potentiometer

What are the main functions of potentiometer in the circuit? Knowing the main functions of potentiometers can help you become more familiar with potentiometers. Let's get familiar with the main functions of potentiometers

the main functions of potentiometer in the circuit are as follows:

1 As a voltage divider, the potentiometer is a continuously adjustable resistor. When the rotating handle or sliding handle of the potentiometer is adjusted, the moving contact slides on the resistor body. At this time, the output voltage that is related to the maintenance method of potentiometer 1 and spring fatigue testing machine and the angle or stroke of the movable arm can be obtained at the output end of the potentiometer

2. When used as a rheostat

potentiometer is used as a rheostat, it should be connected into devices at both ends, so that a smooth and continuously changing resistance value can be obtained within the travel range of the flower potentiometer

3. As a current controller

when the potentiometer is used as a current controller, one of the selected current output terminals must be the sliding contact outlet

working principle of potentiometer

and flexible data recording method

from the outside, the pulse potentiometer is the same as the ordinary potentiometer with three pins, but inside it, two metal static plates of different lengths are connected with pins 1 and 2, and the metal moving plate with 12 or 24 teeth around is connected with pin 3. When the pulse potentiometer rotates, there are four states: pin 3 is connected to pin 1, and pin 3 is fully connected to pin 2 and pin 1; Pin 3 is connected to pin 2, and pin 3 is completely disconnected from pin 2 and pin 1

in practical use, pin 3 is generally grounded as the data input. Pins 1 and 2 are connected to the i/o port of the single chip microcomputer as data output terminals. As shown in Figure 2, connect pin 1 to P1.0 of the single chip microcomputer, and pin 2 to P1.1 of the single chip microcomputer. When the pulse potentiometer rotates left or right, P1.0 and P1.1 will periodically produce the indicated waveform. If the 12 o'clock pulse potentiometer rotates for one turn, 12 sets of such waveforms will be generated, and the 24 o'clock pulse potentiometer will produce 24 sets of such waveforms; A set of waveforms (or a cycle) contains four working states. Therefore, as long as the waveforms of P1.0 and P1.1 are detected, we can identify whether the pulse potentiometer rotates left or right

main parameters of potentiometer

the main parameters of potentiometer include nominal resistance, rated power, resolution, sliding noise, resistance change characteristics, wear resistance, zero resistance, temperature coefficient, etc

1. The nominal resistance value and rated power of the potentiometer

2. The resistance value marked on the potentiometer is called the nominal resistance value

3. The rated power of potentiometer refers to the maximum power allowed to be consumed by long-term continuous load under the specified rated temperature in DC or AC circuit when the atmospheric pressure is 87~107kpa. The rated power series of wire wound and non wire wound potentiometers are shown in Table 2

meter 2 potentiometer rated power nominal series (unit: power)

resistance change characteristics of potentiometer

resistance change characteristics refer to the relationship between the resistance value of potentiometer and the length of movable contact or the rotation angle of rotating shaft, that is, the resistance value output function characteristics. There are three commonly used resistance variation characteristics, as shown in the figure

figure potentiometer resistance change curve

linear type (X type): with the change of the position of the moving corner, the change of its resistance value is close to a straight line

exponential type (Z type): the change of potentiometer resistance is exponentially related to the change of moving corner position

① the resistance change of linear potentiometer is in line with the rotation angle. When the conductive material on the resistor is evenly distributed, the resistance value per unit length is roughly equal. It is suitable for occasions requiring uniform adjustment (such as voltage divider)

② due to the uneven distribution of conductive materials on the resistor, the resistance of the exponential potentiometer changes slowly when the potentiometer starts to rotate, and changes steeply when the rotation angle increases. The allowable power of the exponential potentiometer per unit area is different, and the end with small resistance change is allowed to bear larger power. It is widely used in volume adjustment circuits, because the human ear is the most sensitive to the loudness of sound. When the volume is high to a certain extent, the human ear gradually becomes dull. Therefore, the volume adjustment generally adopts exponential potentiometer to make the sound change appear stable and comfortable

③ because the distribution of conductive materials on the resistor is also uneven, the resistance value of the logarithmic potentiometer changes quickly when the potentiometer starts to rotate. When the rotation angle increases, the resistance value changes slowly when it is close to the end with large resistance value. Logarithmic potentiometer is applicable to electronic circuits that have the opposite requirements to exponential potentiometer, such as contrast control circuit and tone control circuit of TV

potentiometer resolution

potentiometer resolution is also known as resolution. For wire wound potentiometers, when the moving contact moves every turn, the output voltage changes discontinuously, and the ratio of this change to the output voltage is the resolution. The theoretical resolution of the linear wire wound potentiometer is the reciprocal of the total number of turns of winding n, which is expressed as a percentage. The more the total turns of the potentiometer, the higher the resolution

maximum working voltage of potentiometer

the maximum working voltage of potentiometer refers to the maximum allowable working voltage that the potentiometer can withstand without damage under specified conditions for a long time, which is also called rated working voltage

The actual working voltage of the potentiometer should be less than the rated working voltage. If the actual working voltage is higher than the rated working voltage, the power borne by the potentiometer will exceed the rated power, which will cause the potentiometer to overheat and damage

dynamic noise of potentiometer

when the dynamic contact point of potentiometer slides on the resistor under the action of applied voltage, the electrical noise generated is called the dynamic noise of potentiometer. Dynamic noise is one of the main parameters of sliding noise. The value of dynamic noise is related to the speed of the rotating shaft, the contact resistance between the contact point and the resistor, the uneven change of the resistivity of the resistor, the number of dynamic contact points and the applied voltage

potentiometer structure and type

potentiometer is composed of shell, sliding shaft, resistor and three leads, as shown in the figure. There are many kinds of potentiometers, which can be divided into rotary (or rotary handle) and direct sliding potentiometers according to the adjustment mode; According to the number of connections, it can be divided into single connection type and multi connection type, which can completely and effectively eliminate the possible problem locator; According to whether there is a switch, it can be divided into two types: no switch and with switch; According to the characteristics of resistance output function, it can be divided into linear potentiometer, exponential potentiometer and logarithmic potentiometer. Solid core potentiometers, chip potentiometers, carbon film potentiometers, glass glaze potentiometers, high molecular materials in China will meet new challenges and opportunities, precision conductive plastic potentiometers and other potentiometers

application of potentiometer

(1) dimming table lamp circuit

Figure 4 shows a simple and practical dimming table lamp circuit. Adjusting the resistance value of RP can change the time when the capacitor C is charged to UG value, that is, adjust the conduction angle of the thyristor so that the thyristor triggers conduction earlier or later, so as to adjust the output voltage of the thyristor so that the voltage at both ends of the lamp can change between 0~220v. The voltage is high, and the lamp is bright; The voltage is low and the light is dim

figure structure diagram of ordinary potentiometer

figure dimming table lamp circuit

(2) DC regulated power supply circuit

DC regulated power supply circuit is shown in the figure. Generally, R4 can choose low-power carbon film potentiometer and RP can choose high-power wire wound sliding potentiometer. Adjusting the resistance value of R4 can change the output voltage u, and adjusting RP can test the load capacity of the power supply

potentiometer connection

general potentiometers, the middle is the moving piece, so when measuring resistance, 1. Pin 3 is the total resistance, and the resistance value will not change when the moving blade moves. If you connect 12, the resistance value will increase from clockwise (if the moving blade moves), and if you connect 2 and 3, it will be reversed The six pins are called duplex potentiometers, that is, two single ones are made together. The eight pins should have a switch, which is usually used in car stereo

Copyright © 2011 JIN SHI