trimpot question

Discussion in 'General Electronics Chat' started by 1-3-2-4, Apr 13, 2013.

  1. 1-3-2-4

    Thread Starter Active Member

    Dec 26, 2008
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    If I wanted to replace it with a resistor do I measure the left and right pins to the wiper to get the total resistor value I would need right?
     
    Last edited: Apr 13, 2013
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    depends on how it is connected in the circuit. Some trimpots are connected with viper shorted to one end, so you need to check which part of the resistance you want.
     
  3. 1-3-2-4

    Thread Starter Active Member

    Dec 26, 2008
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    It's nothing but connected to a 3-position switch, it's for a midi project. I had trimpots on..

    the midi controller it's self has +/- and the wiper pin hook up. My wire hook up was, ground went to the comm on the switch then to the first leg of the trimpot then each was connected.

    My thing was to run each resistor from each switch position so I can save on space.. You can see a shot I took a few hours ago.

    [​IMG]
     
  4. BillB3857

    Senior Member

    Feb 28, 2009
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    If all three terminals of the pot are connected to different circuit paths, you will need two resistors. One would represent the resistance from the wiper to one end and the other would represent the resistance from the wiper to the other end.
     
  5. 1-3-2-4

    Thread Starter Active Member

    Dec 26, 2008
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    is it possible for a 10k trimpot to show 10 ohms on one lead? I'm not sure why it's showing that

    I just noticed I don't need a resistor for one of the switches, that high number is because that trimpot is turned to it's max travel so a jumper wire would be all I need.
     
    Last edited: Apr 13, 2013
  6. 1-3-2-4

    Thread Starter Active Member

    Dec 26, 2008
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    So all in all I would need 3 resistors for one trimpot? Hmm.. I might be better off just sticking with the trimpots then.
     
  7. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    two, not three.
     
  8. 1-3-2-4

    Thread Starter Active Member

    Dec 26, 2008
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    I'm looking for my vertical trimpots now, a lot of the resistors I would need I don't have and space is limited.
     
  9. ScottWang

    Moderator

    Aug 23, 2012
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    If using three positions to represent the values of pot, it will be as 1,2,3, the 1 is the left side and the 2 is the middle, and the 3 is the righ side.

    Which position do you need(1,2,3)?

    If you turn the pot to the left side and 1,2 pin will going to zero Ω, but it can't be zero Ω, because it was made of carbon, it will left a little resistance between 1,2 pin when you turn to left side, and it will left a little resistance between 2,3 pin when you turn to the right side, when the values of pot more higher then the resistance will more higher.
     
    1-3-2-4 likes this.
  10. 1-3-2-4

    Thread Starter Active Member

    Dec 26, 2008
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    well I wanted to see which resistors I would need to connect the other resistors but I noticed I can't make most of them without it being very cluttered with resistors.
     
  11. ScottWang

    Moderator

    Aug 23, 2012
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    Draw the circuit and unsolder the components then you will see those parts on the paper, it's more easy to do the next step.
     
  12. 1-3-2-4

    Thread Starter Active Member

    Dec 26, 2008
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    Well I got one resistor in place but still stuck I checked the right & wiper on the first pot and I placed my resistor.. So now checking the left & wiper I'm still getting 10 ohms.. so I hooked it to the meter and started turning, and about the last 1/4 of a turn it jumps from kohms to ohms now that's that one.. i have a 100k pot that does not do that.
     
  13. ScottWang

    Moderator

    Aug 23, 2012
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    >it jumps from kohms to ohms now that's that one

    If the general pot happened something like that is abnormal, could be the carbon already destroyed at that section, I have been disassembly some general pots, but I haven't see the pot like this one.

    If you have the item number then you could check the datasheet.
     
  14. 1-3-2-4

    Thread Starter Active Member

    Dec 26, 2008
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    ok all done with just one issue.. if I move the switch at some speed settings it thinks I made a jump to a higher value.. I did not notice this with the trimpot last night, lucky for me it's not going to make a big deal but it's a bunch of extra data I don't care to see.. Is it possible to avoid this?

    I made a video.
    http://www.youtube.com/watch?v=AeVsB2l_Ne8

    *edit

    I was told it was because I trimmed the contact to make a break-before-make If I had left it the other way _make-before-break it would of been fine.
     
    Last edited: Apr 13, 2013
  15. ScottWang

    Moderator

    Aug 23, 2012
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    As what you moving on the video that it looks like a switch and adding some resistors, it doesn't like a trimpot.

    So could you draw the circuit, including the switch and the resistors and measuring the resistors of the switch when they are at three different positions.
     
  16. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Does that midi box really need to be set with trimmers outside, cant it be done in the programming?
     
  17. 1-3-2-4

    Thread Starter Active Member

    Dec 26, 2008
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    I ended up taking them out because of space, I pretty much got my same numbers as I did when I was using the trimpots

    using a 4.7k, 2.2k, 100k & 1k
     
  18. 1-3-2-4

    Thread Starter Active Member

    Dec 26, 2008
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    I wish :(

    I'm using resistors now anyways so it's not as bulky.
     
  19. 1-3-2-4

    Thread Starter Active Member

    Dec 26, 2008
    194
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    Well it's done too bad I don't have a lot of 1/4W resistors, could of saved more space.
     
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