Introduction
The potentiometer is a three-terminal resistive element whose resistances can be adjusted according to a certain change rule. According to it, it is used in a large variety of electrical and electronic circuits, such as voltage dividers, variable resistor, and current controllers. The potentiometer is usually composed of a resistor body and a movable brush. When the brush moves along the resistor body, the resistance value or voltage will be changed at the output end. Due to its special structure and function, it is necessary to pay attention to its damage and take regular maintenance during operation.
1 Potentiometer Using Tips
1) The resistor body of the potentiometer is mostly made of polycarbonate synthetic resin. Avoid contact with the following items: ammonia, other amines, aqueous alkali solutions, aromatic hydrocarbons, ketones, lipid hydrocarbons, and strong chemicals (excessive acid-base value), etc. Because chemical reaction with those will affect their performance.
2) The terminal of the potentiometer should avoid using water-soluble flux when soldering, which will cause metal oxidation and mold material. In addition, avoid using inferior flux, and poor soldering may cause difficulty in soldering, resulting in poor contact or open circuit.
3) If the soldering temperature is too high or the soldering time is too long, it may cause damage to the potentiometer terminals. The pin terminal should be soldered at 235℃±5℃ within 3 seconds, and the soldering space should be more than 1.5mm away from the potentiometer body. Do not use solder to hit through the circuit board when soldering, and wire terminal soldering should be soldered at 350℃±10℃ within 3 seconds. Except that, the terminal should avoid heavy pressure, otherwise it is easy to cause poor contact.
4) During soldering, the height of the rosin (flux) entering the printing machine board should be adjusted properly, and the flux should be prevented from entering the potentiometer, otherwise it will cause poor contact between the brush and the resistor, resulting in INT, noise and other undesirable phenomena.
5) The potentiometer is best used in the voltage adjustment, and the connection method should choose “①” pin grounding. The current adjustment structure should be avoided, because the contact resistance between the resistor and the contact piece will stop the passage of large currents.
6) Avoid condensation or water droplets on the surface of the potentiometer, and avoid using it in a humid place to prevent insulation deterioration or short circuit.
7) When installing the rotary potentiometer, the strength should not be too tight to avoid damage to the screw teeth or poor rotation. When install the sliding type potentiometer, avoid using too long screws, otherwise it may affects the movement of the sliding handle, and even directly damages the potentiometer body.
8) In the process of putting the potentiometer on the knob, the pushing force used should not be too large (not exceeding the parameter index of the pushing and pulling force of the shaft in the specification note), otherwise it may cause damage to the potentiometer.
9) The operating force (rotation or sliding) of the potentiometer will become faster as the temperature rises, and slower as the temperature drops. If the potentiometer is used in a low temperature environment, it needs a kind of special low temperature resistant grease.
10) The shaft or sliding handle of the potentiometer should be as short as possible when designing it. The shorter the shaft or sliding handle, the better and stable the hand feel. On the contrary, the longer the shaking, the greater the shaking, and the feel is easy to change.
11) The power of the carbon film of the potentiometer can withstand the ambient temperature of 70°C, and its function may be lost when the temperature is higher than it.
12) The resistor body of the sealed potentiometer is mostly made of polycarbonate synthetic resin. Avoid mixing with ammonia, aromatic hydrocarbons, lipid hydrocarbons, ketones, and strong chemicals (excessive pH), other amines, alkaline aqueous solution, etc, because they will affect its performance.
2 How to Clean Potentiometer?
The potentiometer is to wrap the carbon sheet with POM, PC, ABS and other plastic materials. After assembly, the carbon sheet will not be exposed to the outside, it is not easy to oxidize, and dust is not easy to enter, which protects the potentiometer body.
Cleaning Steps of Potentiometer
1) Use a screwdriver to carefully open the sealing cover fixing card of the sealing potentiometer, and remove the protective cover.
2) Remove the fixed spring card of the rotating shaft and pull out the rotating shaft.
3) If some sealed potentiometers cannot take out the shaft, you can directly wipe the carbon film and the metal contacts on the shaft with a cotton ball dipped in pure alcohol.
4) Adjust the position and angle of the metal contacts, changing the contact position with the carbon film and increasing the pressure.
5) Apply some lubricating oil or special grease on the carbon film to delay the service life.
6) Reinstall and fix the metal cover to complete the entire cleaning process.
4 Replacing Potentiometer with 4 Steps
There are many types of potentiometers, and most models cannot be used interchangeably, otherwise the control effect will not be very good. When replacing it, the nominal resistance value should be the same as the damaged variable resistance value or the close to. At the same time, its packages must be considered, otherwise the installation will be difficult. Therefore, we must distinguish between linear potentiometers, exponential potentiometers and logarithmic potentiometers before use. In addition, please note that the precision resistor can only be replaced with a same one when it is damaged, and cannot be replaced with an ordinary variable resistor, otherwise its adjustment accuracy will also be affected.
The potentiometer has multiple pins. In order to prevent the wrong pins from being connected during replacement, the following specific operation steps and methods can be used:
Step 1: Remove the set screw of the original potentiometer, but do not take off the leads on the potentiometer.
Step 2: Install the new potentiometer and fix it.
Step 3: Solder a lead on the original potentiometer pin slice, solder it on the corresponding pin slice of the new potentiometer, and the welding method is the same as the old one.
Step 4: In the same way, solder each pin wire. Pay attention, welding the next one and then the other one can avoid the wrong position of the leads being welded to each other.
Get complete info from How to Maintain Potentiometer and Its Replacements.
