Need help with hobby project

Discussion in 'General Electronics Chat' started by Mason Dixon, May 2, 2010.

  1. Mason Dixon

    Thread Starter New Member

    May 2, 2010
    3
    0
    I am trying to piece together a motor, and speed controller for a tub grinder(basically a turntable) as cheaply as possible. It has to be high torque tho, at least 1/2hp motor and low speed(0-50rpm).

    I know next to nothing about electronics. Is it possible to use some kind of AC motor(with a potentiometer for the speed control) for this so I can plug it into a standard home socket? Or is this something only DC gear motors can do? Which would mean I have to buy an expensive power supply/converter?
     
  2. VoodooMojo

    Active Member

    Nov 28, 2009
    503
    53
  3. Mason Dixon

    Thread Starter New Member

    May 2, 2010
    3
    0
    Thanks

    Will a speed controller slow a salvaged washing machine 1725 motor down to 0-50rpm's and still keep the 1/2 hp torque?

    Basically I'm trying to build a pottery wheel on the cheap.
     
  4. VoodooMojo

    Active Member

    Nov 28, 2009
    503
    53
    I would suspect you could accomplish most of the RPM reduction by using the appropriate pulley sizes. and with that much speed reduction you should have power out the yin/yang.
     
  5. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    Voodoomojo is right. Gearing is the way to keep torque while reducing speed.

    For DC, PWM is a way of pulsing the motor to produce a duty cycle that changes speed while keeping torque, but alas your motor is most likely AC, so no dice.

    If you can find a DC motor it will work.

    Do you have the gearbox from the washing machine? It should have the gearing to spin the drum to around 100 RPM, so a 2:1 pulley would have you there. Many machines have two spin speeds. Pulling that open will offer you much help.

    Once you have a gear box, you can slow the motor slightly, and in turn, slow the gearbox output significantly without too much torque loss.
     
  6. Mason Dixon

    Thread Starter New Member

    May 2, 2010
    3
    0
    Thanks for the help. I'm thinking a bicycle wheel/chain pulley system will help to reduce rpm's.
     
  7. VoodooMojo

    Active Member

    Nov 28, 2009
    503
    53
    keep it simple
    1725 RPM can be reduced to 50 RPM by putting a 3 inch pulley on the motor and an 18 inch pulley on the table.
    The speed controller can reduce the speed from there without effort.
     
  8. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    I have done this, and it works. I use one of those 10 speed-type bikes that have the push button, upshift / bush button downshift, and used 2 solenoids to control it.

    A opto tachometer on the wheel, reported speed to a uC and it upshifted or downshifted as required to keep my RPMs in range.

    I used this on a wind turbine thats speed changes with the wind, so I needed a way to handle gusts.

    Worked GREAT....but.... I live in the city, so too loud for the neighbors.

    But listen to VoodooMojo. You can find a 18 inch wheel (maybe from the bike) and a 3 inch gear (from the bike)
    your set.
     
  9. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    No, you can't use a speed controller on that particular type of motor; it's a "squirrel cage" type induction motor, not a universal motor, and it's designed to be operated on 60Hz.

    You might be able to control it using a VFD (variable frequency drive) - but such things are anything but cheap.

    Your best bet is likely going to be a pulley reduction system, like VoodooMojo suggested.

    Alternatively, you might consider fitting a piece of tubing (like automotive heater hose) over the motor's shaft, and using that to drive the edge of the potter's wheel. However, you'll have to figure out a way to keep the motor from getting wet.
     
  10. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    If you use the potters wheel as the 2nd pully, you need only calculate the pulley size for the motor shaft, and use a belt..

    (I see your post now Sarge)

    To keep the motor from getting wet, install the motor shaft side down. a decent distance from the wheel. A splash shield will be in order, also.

    Because the belt WILL get wet, you dont want the water and clay dripping into it. So, if it is upside down, it will follow gravity (for the most part) and the splash shield can be made to keep "slinging" contained.

    PS. Water and electricity don mix. BE CAREFUL
     
Loading...