DC motor speed controt rheostat change

Discussion in 'The Projects Forum' started by Murrell, Nov 19, 2008.

  1. Murrell

    Thread Starter New Member

    Nov 16, 2008
    I have very little knowledge on control wireing, so bear with me:

    I am working on a project, useing a treadmill motor & controls to operate my honey extractor, It works Great !

    Now I have 2 problems,
    #1- I want to change the Speed control slider rheostat to
    a rotary one so it will fit in my control box.
    Info. printed on the slider is;
    FO1-150M, POT2B, Long Slide Pot, AW REV. B
    [ the post are marked L,W,& H all three post being used, very small wire I'd guess at about 20 ga. or less which go to a Motor Controller Model MC 40 ]

    Only other info I have on the this is the test procedure;
    " Turn pot to low speed & observe restiance as pot is turned to high speed; Resistance should rise to appx. 4K-5K at W & H post "

    What size Rotary Rheostat am I looking for ?

    #2- I also want slow the Motor speed control down so the rheostat is not as senstive, the motor is;
    DC - Volts 100 - 5100 RPM - 1.5 HP

    My speed needs are; starting abt. 35 RPM then progressing to a max of abt. 325 RPM .

    The current Rheostat above does this but, the slide movement is only about 3/8 in. [ full range is abt. 3.5 in of slide ]

    Will a second Rheostat wired in Series work ?

    I went to Radio Shack, they knew less then I do, They were more interested in selling me a cell phone.

    I hope I haven't bored you too much.

    Thanks everyone for your time and consideration.

  2. nomurphy

    AAC Fanatic!

    Aug 8, 2005
    It sounds like the pot is part of the electrical circuit for the controller. It is doubful that anyone is going to have enough info on the controller to know the design specifics or requirements for the pot. It is probably controlling the gate voltage to an SCR, or something much more complicated (there are a lot of options). So, unless you can Google something specific on the pot based on its numbering, you're probably out of luck.

    However, if you have an ohm meter (DMM) and disconnect the pot wires, you could measure the resistance of the pot. Someone may be able to guess the wattage based upon the physical size, but that's only a chance.
    Last edited: Nov 21, 2008