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Big DC Motor Speed Control

Discussion in 'Sensors and Actuators' started by JohannS, Oct 15, 2016.

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  1. JohannS


    Oct 15, 2016
    Hello, all!

    I will admit straight away that this is out of my field of expertise, but I enjoy challenges and I particularly enjoy building electronics projects. I have some basic experience with making AC-DC converters from scratch, but only at the ~5V level (for a bicycle Dynamo generator to USB phone charger). I am now hoping to accomplish a considerably more advanced task:

    I have the following motor:

    It's pretty big and seems to have pretty high voltage and amp demands, but maybe it just seems like that to me (a relative novice).

    I am trying to use this motor to rotate a pottery wheel. I plan to use a pulley to gear down the rpm (actual table rotation only needs to be between 0-200rpm). But within that range, I'd like to be able to control it with a foot pedal.

    For the record, I tried to find a motor that closely resembled the one used in a high-end commercial pottery wheel. That motor had the following specs:

    The "real" motor (that is, the one designed and used in the professional product) has a higher wattage in the end, but I don't think the different will really matter for this application.

    My first instinct (for speed control) is a potentiometer, but I'm just not sure if any commercially available potentiometer can deal with that current (7.6A). Is there something available that I just haven't seen? Will my motor run on a lower current?

    Am I going to have any serious problems with the AC/DC conversion using the basic bridge rectifier/capacitor setup? What kind of components would suffice (if any)? Is there another solution?

    I'm trying to keep this project on the inexpensive side. I got the motor for a steal. The pottery wheel I'm modelling this after is $1500, and with all of the table materials and motor, I'm under $100. If I can put the power converter and speed control pedal together for less than a couple hundred, I'd say that's a pretty good savings. And I also get to enjoy the process.

    [Side note: should I just scrap the whole electronics idea and just go for some kind of transmission? It's not very elegant and would require many more moving parts, but I'm open to it if my original idea is truly untenable.]

    Like I said at the outset, this is not my profession. Just tell me honestly if this is way above my head or if I will kill myself along the way. I'm a strong believer in mocking things up, computer simulation, theory, and controlled testing, so I won't be just connecting things willy nilly.

    I deeply appreciate any help this community may be able to offer. This is (hopefully) going to be a gift for my wife who does pottery as a sort of therapy and to whom this craft serves as one of the most positive aspects of her life. This wheel could give her the ability to work at home (rather than once/week at a local shop). We just aren't in a position to put down the kind of money these things sell for, and I think the act of my building it will have special value to both of us.

    Once again, thank you all for reading and helping.
  2. davenn

    davenn Moderator

    Sep 5, 2009
    Hi Johann
    welcome to EP

    These are not really questions you should be asking on a forum, considering your admitted inexperience
    You really need to find someone close to you in your town/city that can directly mentor you face to face

    With the voltages and currents required for this project, it's just too dangerous to work on your own, failure to do things correctly
    could result in huge current flows and flash over arcs

    Please be safe and get local personal guidance from a registered electrician

    for the above reasons, the thread is closed

    Anon_LG likes this.
  3. davenn

    davenn Moderator

    Sep 5, 2009
    we are always here to help you on more reasonable projects :)
    Anon_LG likes this.
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