Paralleling Pots

Discussion in 'General Electronics Chat' started by PackratKing, Dec 4, 2013.

  1. PackratKing

    Thread Starter Well-Known Member

    Jul 13, 2008
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    OK Guys and gals... I said I would post any observations, so here goes...

    Any Pot, can really only be paralleled with a matching resistance, to reduce its fixed element resistance by ~1/2... and enhance its wattage... maybe equal to 25-50% more wattage than the pots' own element will tolerate.

    Any more than 20% deviation, Linearity, or degrees of rotation that remain effective, go out the window in a hurry.

    Is messing with the wattage in that manner going to cause the pots' element to burn up sooner, or will the Ohms-law equal division of current through two or three conductors, make the pot able to endure an application carrying more current ??

    These are things novices do to learn -- good thing I have a [ packrat ]supply of pots and resistors, so I don't really care if I burn a few up in the process... the price of experience :D
     
  2. wayneh

    Expert

    Sep 9, 2010
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    Don't do it!

    Murphy's Law dictates that someone will come along and turn both pots to one end or the other and destroy both of them. If you want to protect a pot, put some minimum resistance in series with it so that it won't roast even if turned all the way.

    And if you need to tailor a pot, I can supply a few good references for you. If you're handy with math and a spreadsheet, you can easily evaluate what different configurations will look like.
     
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    +1000 exactly
     
  4. PackratKing

    Thread Starter Well-Known Member

    Jul 13, 2008
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    Oops..:eek: maybe a picture is in order...

    I am meaning to apply a fixed resistor parallel to the internal element of the pot, on the outer two legs, and draw my current off the wiper tap...

    not physically parallel two pots... I have already discovered that is a disaster :D unless the pots are stacked/identical on a common shaft. ...then solder the legs together...

    Thank you both for guidance, it is very much appreciated... I need to better understand what wayneh means by the resistor in series...
     
    Last edited: Dec 4, 2013
  5. ScottWang

    Moderator

    Aug 23, 2012
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    Why you want to in parallel with the pots?
    What is your purpose of the experiment?
    Any circuit?
     
  6. PackratKing

    Thread Starter Well-Known Member

    Jul 13, 2008
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    Hi Scott...

    Purpose of this, it seems that unless you want to advance to a variac, or some rather expensive pots, or an ohmite rheostat, of which I have a bunch, this is the easiest way to get a unit rated at more than one watt...

    I am building a multi-voltage power supply, and the adjustable regulators configured as series pass with a t'sistor, call for a hefty pot... This is an attempt to cheap out a little..:rolleyes: to save the quality components after the bugs are hammered out, for the final construction.
     
    Last edited: Dec 8, 2013
  7. crutschow

    Expert

    Mar 14, 2008
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    How do you propose to operate both shafts in synchronism?
     
  8. PackratKing

    Thread Starter Well-Known Member

    Jul 13, 2008
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    I don't ! :eek: ...it's a mystery to me where you got that idea :confused:
    I have some salvage units, for example, that are two 100K pots stacked together on a common shaft, with their legs bent together and soldered, making a 2-unit 50 k config, with twice the watt rating.

    Ohms law dictates a 50/50 current split betwixt the two elements = more wattage !!
     
    Last edited: Dec 8, 2013
  9. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    What sort of wattage are you looking for?
    4 or 5+W pots are easily available..
     
  10. PackratKing

    Thread Starter Well-Known Member

    Jul 13, 2008
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    And I'm quite sure I have some... among my packrat collection... however, it's more fun to use what you have on hand, and bend physical laws making do with what you have, breadboard the lesser quality first, until certain the circuit will hold up to some normal abuse, then beef it up with the good ones to produce the finished product... :rolleyes:
     
    Last edited: Dec 4, 2013
  11. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    ahhh.. A packrat el-cheapo style.. Gotcha..
     
  12. PackratKing

    Thread Starter Well-Known Member

    Jul 13, 2008
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    Not exactly... It is common, is it not, to breadboard and hammer out bugs with components that are relatively expendable, and build the finished product with the best components...
     
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