What the Reason That Potientialmeter Failed and Work Again
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Introduction
Potentiometers are widely used and are commonly used electronic components in circuit design. They are adjustable and are considered as one of the variable resistors. In general, it is constructed by a resistor carrying box rotation/sliding organisation. More often than not speaking, a moving contact is moved on the resistor body to obtain a part of the voltage output.
Catalog
Ⅰ How Does a Potentiometer Work
Viewed from the outside, the pulse potentiometer is the same equally the ordinary potentiometer. It is connected to pins 1, 2 and is continued to two metal mats of different lengths. It is connected to pin three in a circle. Metal slides with 12 or 24 teeth. When the pulse potentiometer rotates, 4 states can appear: pin 3 is connected to pin ane；pin 3 is connected to pin 2 and pin 1; pin 3 is connected to pin 2； pins 3 is disconnected to Pivot 2 and pin 1.
In applied use, pin 3 is mostly grounded as the data input terminal. Pins 1 and ii are continued with the IO port of the single-flake computer equally data output terminals. As shown in the effigy, pin 1 is continued with the single-chip microcomputer'due south P1.0, pin 2 is continued with the single-fleck computer'southward P1.ane. When the pulse potentiometer is left-handed or right-handed, P1.0 and P1.one periodically produce the waveforms shown. If the 12-point pulse potentiometer rotates in one case, 12 sets of such waveforms will be generated, 24 sets of such waveforms will exist generated by the 24-indicate pulse potentiometer; a set of waveforms (or a cycle) contains iv working states. So as long every bit the waveforms of P1.0 and P1.1 are detected, whether the pulse potentiometer rotates left-handed or correct-handed tin be identified.
When a voltage is applied betwixt two fixed electrical shocks of the resistor body, the position of the contact on the resistor body is changed through the rotation or sliding arrangement, and the position of the movable contact is obtained between the movable contact and the fixed contact. There is a certain relationship betwixt voltages. The potentiometer is a four-final component, which is mainly used as a voltage divider. The potentiometer is a kind of adjustable electronic component, which is basically a sliding rheostat. There are several styles of potentiometers, which are generally used for speaker book switch and laser caput power adjustment.
How Potentiometer Assembles and Works
When the rocker potentiometer is used as a electric current adjustment in the DC circuit, at that place volition be a current passing through the sliding arm of the rocker potentiometer, and the resistance value will increase abnormally due to the anodization. In this instance, it is recommended to connect the terminal to which the resistor is connected to the negative pole and the sliding arm to the positive pole. If the direct electric current directly passes through the rocker potentiometer, the anode of the rocker potentiometer will be oxidized and damaged, and then that the impedance of the rocker potentiometer becomes larger.
Therefore, it is better to connect the negative pole of the electric current to the terminal that is in contact with the carbon diaphragm. Upper, the positive pole is connected to the terminal of the brush (rocker potentiometer contact piece). When the rocker potentiometer is used every bit a variable resistor, information technology is recommended to use a voltage divider for adjusting the voltage. At the same time, the load resistance RL of the rocker potentiometer should be no less than 10 times the nominal resistance of the rocker potentiometer.
For the volume rotation aligning knob on the radio, a potentiometer is generally required. The potentiometer is mainly composed of three atomic number 82 terminals, of which at that place is a fixed resistance betwixt the two stock-still terminals, and the other end slides on the resistance through the contact. Notwithstanding, because the potentiometer is an electromechanical component. It relies on the sliding of the castor on the resistor body to obtain an output voltage that has a certain human relationship with the displacement of the castor, then the resistance value of the potentiometer from the sliding end and the fixed end will change with the change of the position of the sliding end. In other words, the radio potentiometer obtains different signal voltages past changing the position of the sliding end on the resistor body, thereby realizing the adjustment of the performance control volume.
Ⅱ Potentiometer Wiring
2.1 How to Wire a Potentiometer
The potentiometer is a resistance element with iii front ends, and its resistance value can exist adjusted according to a certain modify rule. The potentiometer is usually equanimous of a resistor and a movable castor. When the brush moves along the resistor, the resistance value or voltage related to the displacement is obtained at the output final.
The potentiometer tin can be used as a three-terminal component or as a 2-terminal component. The latter can be regarded equally a variable resistor, and since it functions in the circuit to obtain an output voltage that is related to the input voltage (applied voltage), it is called a potentiometer.
The potentiometer is a continuously adjustable resistor. When adjusting the knob or slider of the potentiometer, the movable contact slides on the resistor body. At this time, at the output end of the potentiometer, the output voltage related to the voltage practical by the potentiometer and the angle or stroke of the movable arm can be obtained.
When the potentiometer is used as a varistor, it should be connected to the two ends of the device, so that a smooth and continuously changing resistance value can be obtained within the stroke range of the potentiometer. When the potentiometer is used as a current controller, one of the selected current outputs must be the sliding contact last.
ii.2 Potentiometer Structure
(1) Carbon Film Potentiometer Structure
Figure 1. is a schematic diagram of the construction of a carbon moving picture potentiometer.
Figure 1. Carbon Film Potentiometer Structure
(2) Multi-turn Potentiometer Structure
Effigy 2. is a schematic diagram of the structure of a multi-turn potentiometer.
Figure 2. Muti-turn Potentiometer Structure
2.3 How to Use a Potentiometer
When the potentiometer handle rotates, the rotor slides on the resistor torso and the resistance between the GK105 rotor and the 2 stators changes. When the resistance of the moving office to one fixed part increases, the resistance of the moving role to the other fixed part decreases, as shown in Figure 3. When the resistance of the rotor to 1 stator decreases, the resistance of the rotor to the other stator increases.
Figure 3. Potentiometer Adjustment Resistor
The potentiometer is also equivalent to a serial circuit composed of two resistors in the circuit. The rotor divides the resistor body of the potentiometer into 2 resistors R1 and R2, as shown in Figure four.
Figure iv. Potentiometer Equivalent Serial Excursion
When the moving part slides toward the fixed end one, the resistance of R1 decreases, and the resistance of R2 increases. When the moving part slides toward the fixed end 2, the resistance of R1 increases, and the resistance of R2 decreases. The sum of the resistances of Rl and R2 is ever equal to the nominal resistance of the potentiometer.
The master requirements for the potentiometer are:
(1) Resistance meets the requirements.
(ii) The contact betwixt the center sliding stop and the resistor torso is good, and the rotation is smooth.
For potentiometers with switches, the switch parts should be authentic, reliable and flexible. Therefore, the performance of the potentiometer must exist checked before use.
(1) Measurement of resistance value: Kickoff, according to the resistance value of the potentiometer to exist tested, select the appropriate resistance gear of the multimeter to mensurate the resistance value, that is, the resistance value between the ii ends of the Air conditioning, and compare it with the nominal resistance value. Encounter if the 2 are consistent. Rotate the sliding contact at the same time, and its value should be fixed. If the resistance is space, the potentiometer will be damaged.
(ii) And so measure the contact betwixt the center end and the resistance, that is, the resistance at both ends of BC. The method is that the ohm file of the multimeter is within the proper range, and during the measurement process, slowly rotate the shaft. Pay attending to the reading of the multimeter. Under normal circumstances, the reading changes smoothly in i direction. If there is a jump or no drop, the active contact is poorly contacted or malfunctioning.
(3) When the heart end slides to the caput stop, in an platonic land, the resistance value between the eye end and the ancillary end is 0. In the bodily measurement, at that place will exist a sure residue value (generally depending on the nominal value, mostly less than 5 Ω). This is a normal phenomenon.
Potentiometer (or trimming resistor, etc.) conventional pin (only for example, a potentiometer with iii pins), the resistance value of the 2 ends is stock-still, and the resistance value of the pin at either end of the intermediate pin is variable; It is equivalent to dividing the potentiometer into ii series resistors from the middle pivot, and the total resistance of the series is fixed; therefore, if used as a variable voltage divider resistor, i end is connected to the input voltage, and the center terminate is connected to the output, and the rest is left. Last grounding; if used as a variable resistor, i terminate is continued to the input voltage, the middle stop is connected to the output, and the remaining finish can be suspended or connected to the intermediate end.
Ⅲ Potentiometer Repair
3.1 Potentiometer Problems
Mutual potentiometer problems by and large manifest themselves in the internal open up excursion of the pin, the resistor body is burned out, the switch is damaged, the rotating dissonance is besides large, and the resistor body is worn out, etc.
1. Potentiometers are often poorly contacted due to the impairment of the carbon film.
When judging from the appearance that the potentiometer has bad contact and failure, the vanquish can be removed to check the degree of article of clothing. If information technology is only due to poor contact caused past balmy abrasion, the carbon film can be wiped clean with absolute alcohol or carbon tetrachloride, and then the pressure of the sliding arm on the carbon pic tin exist adapted appropriately.
2. There are three cases of potentiometer switch structure damage.
Showtime, the customs are constantly open;
2d, the contact is poor, and the connectedness is not working;
The third is that the switch function is off.
These three types of faults can be detected with a multimeter or can be observed with the naked eye. When repairing, the offset and tertiary boxes must be replaced with new parts. In the second case, the switch tin can exist repaired co-ordinate to the problem. If the contact is bad, the contact is oxidized and the fault can be eliminated. If the spring is weak and the contact is poor, the leap can exist replaced.
three.2 Potentiometer Repair Method
Currently, there are ii main types of potentiometers: one is a potentiometer without a switch, and the other is a potentiometer with a switch. For the use of these two potentiometers, information technology is easy to crusade some problems, such as plough-off or on-off failure, or short excursion caused by poor line contact, and the internal components of the potentiometer fall off. And so how to solve these three types of issues?
First of all, information technology is generally recommended to replace the potentiometer. If the office falls off, it is difficult to restore the original state. Even if they are glued dorsum, they are dangerous in use. Some failures, such every bit poor contact, are generally caused past contact oxidation. Some methods tin can solve this problem, for example, afterwards the potentiometer contacts are wiped clean, the fault is eliminated. Some other situation is that the spring strength of the potentiometer is reduced, causing poor contact and and then on. In this case, a new potentiometer spring can be replaced.
Under normal circumstances, long-term use of the potentiometer will often lead to poor contact betwixt the lines due to damage to the carbon picture show. When the potentiometer can not be folded, you tin can remove the potentiometer shell to bank check the degree of wear of the internal components. For instance, if the reason for poor contact is only the slight abrasion of the potentiometer, some industrial-specific methods can be used to clean information technology, or carbon tetrachloride tin exist used to make clean the carbon film textile of the potentiometer. Later on cleaning, the pressure on the carbon film of the potentiometer slide arm tin can exist adjusted according to the pressure of the slide arm, and so load information technology dorsum.
In the non-linear potentiometer, the leads on the two stators cannot be connected to each other wrongly, otherwise, it volition touch on the command effect of the potentiometer in the circuit. For example, the volume potentiometers of two fixed pins are reversely connected. When you only plow the book knob a little bit, the sound is already loud, but when yous turn the knob again, the volume hardly increases, which is the loss of the linear command characteristics of the volume controller.
At that place are many types of volume potentiometers for power amplifiers, simply the most common one is a double potentiometer, which is used to control the volume of the left and correct channels. It is ordinarily unmarried-centrality, but in that location are as well double-layer dual-axis volumetric potentiometers. The general problems of the volume potentiometer include: when the volume is controlled by rotation, noise is generated, or the volume of the ii channels is different, then the volume potentiometer should be replaced. Afterward the potentiometer is used for a long time, the aging of the carbon film and the appearance of micro-cracks are the principal reason for the decrease in the quality of the book potentiometer. At this time, the volume potentiometer needs to exist completely replaced.
How To Fix a Scratchy Volume Potentiometer?
Ⅳ Oftentimes Asked Questions nigh Potentiometer Problems
1. What is a potentiometer in a circuit?
A potentiometer is a three-last resistor with a sliding or rotating contact that forms an adaptable voltage divider. ... Potentiometers are unremarkably used to control electrical devices such equally book commandsouthward on audio equipment.
2. How is a potentiometer connected in a circuit?
Connect the voltmeter'due south terminals to the input and output terminals on the pot. Turn the voltmeter on and plow the punch to feed a signal. Plow the knob on acme of your pot to adapt the signal. If the signal reading on the voltmeter goes upwards and down when you plow the knob, your potentiometer works.
3. How practise I know if my potentiometer is bad?
First, connect all connection like in this paradigm.
At present, rotate the potentiometer knob using your finger it volition change the Lamp light source High to Low or Low to High. if Lamp light source is change, the potentiometer is good condition or is not alter Lamp light source, the potentiometer is bad condition.
4. What happens when a potentiometer fails?
Potentiometer valve position indicator failures are unremarkably electrical in nature. An electrical short or open will cause the indication to neglect at one farthermost or the other. If an increase or decrease in the potentiometer resistance occurs, erratic indicated valve position occurs.
five. How exercise you test if a potentiometer is working?
Put the probes of your ohmmeter on the two ends. It should read within a few ohms of the rated resistance of your potentiometer. If you become a different reading, 1 of your probes is on the wiper. Try different combinations of two probes until you get 1 that gives you lot the correct reading.
6. Tin a potentiometer be repaired?
Those controls are not available, they have to be repaired. The only way to repair it is to estrus up the tone control shaft with high ability hot iron ( I use 350 Watts solder gun) and special wooden knob I fabricated for this purpose- original plastic knob would melt.
vii. Why copper wire is not used in potentiometer?
Copper has low resistivity and a high temperature coefficient of resistance and hence nosotros practice not apply information technology in potentiometer.
8. How does a 3 wire potentiometer work?
A potentiometer has 3 pins. Two terminals (the bluish and green) are continued to a resistive element and the tertiary final (the black one) is connected to an adaptable wiper. The potentiometer can work as a rheostat (variable resistor) or every bit a voltage divider.
ix. How to Use Potentiometers to Suit Current and Voltage
Connect one cease of the limiting resistor to the positive terminal of the power supply. Attach the other stop if the limiting resistor to one of the fixed terminals of the potentiometer. Link the positive probe of the current meter to the wiper of the potentiometer.
x. How do you reduce the value of a potentiometer?
Nosotros could supervene upon the potentiometer with one of some other value, or nosotros could simulate a lower-value potentiometer by placing a resistor in parallel with it, diminishing its maximum obtainable resistance. This will subtract the bridge of the circuit from 10kΩ to something less.
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