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Universal Motor Control

Discussion in 'Electronic Design' started by 0h1001, Apr 8, 2004.

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  1. 0h1001

    0h1001 Guest

    Hi,

    I have a 110v 5amp universal drill motor. I wish to design a motor
    controller which will allow speed and direction control, and interface at
    TTL to a PIC uC. I can run the motors in AC or DC. The motor is a series
    or universal type which requires the polarity to be switched at the coils in
    order to change direction. There are 4 wires going to the motor, 2 for the
    stator and 2 for the rotor coils. Shorting either side of the coils will
    change the motor's direction.

    I have looked at crydom.com solid state relays to switch coil
    polarities, but it would required 6 relays for each motor. ( running on DC
    and PWM the relay ) I also have looked at using igbt/mosfet combo, but I
    would still need to find a way to change polarity at the coils...

    Can anyone point me to any designs/schematics/appnotes available
    somwhere on the web to accomplish this?

    Cheers,
    Steve
     
  2. CBarn24050

    CBarn24050 Guest

    Most people use a dpdt switch or relay.
     
  3. scada

    scada Guest

    You want an "H Bridge controller" do a Google search....
     
  4. I think the only way ot get something like smooth reversing control is
    to put the armature in series with the power supply to an H bridge PWM
    driver, and connect the output of the bridge to the filed (or switch
    the field and armature). Coming up with an H bridge circuit that
    handles such a variable supply situation will be fun. You are
    beginning to see why universal motors are very rare in servo motor
    applications.
     
  5. scada

    scada Guest

    You could put a bridge rectifier between the Stator winding and the Rotor,
    and run the motor on DC (AC input towards the Rotor, DC out to the Stator).
    That way regardless of the polarity input to the motor, the Stator will only
    see the polarity as you wired it. The downfall to this is that you will drop
    1.4V to the Stator winding (.7 per diode *2), but that should not be a
    problem at 110 VDC. Then you could feed the motor with an H bridge PWM
    controller and have speed control and reverse functions!
     
  6. ACIT

    ACIT Guest

    Thanks. I think you may be on to something. I'll do some diggin around to
    try and understand exactly what you mean. I have 110vac to work with, so I
    will run them at 90vdc or so. The drop in current is no problem. Keep me
    posted if you have any schematics on this setup.

    Cheers
     
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