Dual potentiometer circuit

Discussion in 'The Projects Forum' started by cooksterman, Apr 6, 2012.

  1. cooksterman

    Thread Starter New Member

    Apr 6, 2012
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    I'm building a motorized equatorial platform for a telescope. It will use a small 12v DC motor and a circuit controller (Kit 67 or Carl's Electronics CK1400). The kit is supplied with a 10k pot. I wish to have greater control of the motor. It has been recommended to use a 100-ohm (finer control) or a 200-ohm (coarse control) pot. I would like have both options available. My question is how should the two pots be wired first to achieve coarse control and to then fine adjust the motor? Ultimately the motor will need to turn at a precise pace.

    Thank you:rolleyes:
     
  2. jimkeith

    Active Member

    Oct 26, 2011
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    First thing to do is to establish the maximum voltage and the minimum voltage that you will ever need on the existing pot wiper--then the max speed pot and the min speed pot (now fixed resistor R7) may be scaled for better control of your active speed range--active speed range is probably very limited--this will then make the normal speed pot a much finer adjustment.
     
  3. panic mode

    Senior Member

    Oct 10, 2011
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    i looked up CK1400...
    you could use multi turn potentiometer or if you prefer two controls (coarse/fine) you can do something like this. note that RV2 is coarse adjustment and RV1,RV3 (double pot) is for fine adjustment.
     
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  4. wayneh

    Expert

    Sep 9, 2010
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  5. cooksterman

    Thread Starter New Member

    Apr 6, 2012
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    Thank for your handholding, very helpful direction. My ignorance is only exceeded by my lack of knowledge:)
     
  6. cooksterman

    Thread Starter New Member

    Apr 6, 2012
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    Sorry to take so long...I am a real novice on these things. In your diagram it indicates RV1 and RV3 as 500. Is that a reference to a 500k ohm pot? Does it simply mean that I can insert the pots of choice?

    Thanks for you indulgence.
     
  7. wayneh

    Expert

    Sep 9, 2010
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    He meant a dual 500Ω as drawn (not 500K). A 500K would reverse the coarse/fine roles of the pots, since 500K >> 10K
     
  8. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    656
    Here is another scheme that might work.
     
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