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Random electronics question

Discussion in 'Off Topic' started by kitari, Jan 7, 2015.

  1. kitari

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    Is a potentiometer the same as a variable resistor? If not, what's the difference?
     
  2. crash1sttime

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    I asked google and got this.

    If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat. A potentiometer measuring instrument is essentially a voltage divider used for measuring electric potential (voltage); the component is an implementation of the same principle, hence its name.

    but im no expert
     
  3. PhantomFanatic

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    Not technically. A variable resistor is much larger than a standard resistor. It is wound with wire that has a resistance to it. There are three connections. One at each end and a connection with a metal wiper. The resistance from end to end is constant. But, using one side and the tap connection, the resistance varies when YOU move the center tap. Some circuits use all three connections. There is no shaft or knob. Also, most of the surface is covered except for where the center tap moves. Usually, the setting is held in place by a metal strap, with a flat head screw. It just tightens the clamp where you want it to be set. Rarely are they adjusted frequently.

    A potentiometer (usually called a "pot',) does have a shaft. The round shaft is either metal or plastic. The body is round shaped with three connections. Electrically, it works the same way, except the resistive wire is wound around an almost complete circle on a non-resistive material. There are usually three connections. A rheostat is basically the same thing, but larger and it handles more power. Like a power supply or electric heater.

    There are many types of pots. Some have a shaft, that a knob goes on. Others are very tiny, usually on a printed circuit board and instead of a shaft, it has a plastic flat screwdriver slot. Others are multiple turns. Most pots turn about 300 degrees. These make multiple 360 turns. They are used when a very definitive value of resistance is needed, mostly for calibrating a circuit.

    One pot tip: Bright grow lights. Oh, sorry, I got confused! If a pot, say a volume control on a radio, gets scratchy sounding or it goes quickly from a high volume to a low volume, there is one thing that usually helps, that you can do without taking the radio apart. Grab the knob and turn it back and forth real fast, from the stop on one side to the other stop. Check and see if it is better. If not quite there, try it several times, getting faster with your turns.

    This helps to wipe off any crud that has built up on the pot's resistive wire. This is common on a dial that is a rarely turned or always turned to the same spot. This is a throw away society, but in the ole days, I would take a potentiometer apart and spray the surface with contact cleaner and rotate the shaft back and forth. Sometimes more pressure on the wiper is needed and it can be bent. But, if it is a hassle to open up the device or it is something more important than just volume, it might be worth replacing it.
     
  4. Happyflyer

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    Thanks, PF for the reminders of the old days. I really got a "kick" out of the "grow lights" comment. :cool:
     
  5. kitari

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    oh wow, that really helped me out! I was asking out of curiosity at first, but you actually helped me answer a few questions today. :D
     
  6. PhantomFanatic

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    :)
     
  7. PhantomFanatic

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    You are welcome Kitari. I've got a LOT of brain cells tied up with electronics, so it is nice to exercise them. Now, if I can just make room for Drone stuff!