Motor Controller

Discussion in 'The Projects Forum' started by monkeymanthe1st, Nov 5, 2009.

  1. monkeymanthe1st

    Thread Starter New Member

    Nov 3, 2009
    1
    0
    So for my mechanical engineering class, we are building a rotating tool carousel much like the big ones that they have at Home Depot. We are using a 12 VDC motor from the Mile Marker Pe3500. we are designing so that the amps from the motor will not go above 100A. For the project we need to know exactly where the motor is rotation wise so we are using an absolute rotary encoder to feed that information back to a computer.

    The motor controller needs to be able to vary the voltage to the motor from 0-12V (the maximum output voltage from the controller can be greater that 12V) and it would be nice if it could also send a negative voltage for bi-directional control. We also either need the controller to interface directly with a laptop, or need some way to make it be able to.

    Now, I have been searching for a way to control the rotation on the motor. I have found many motor controllers, but none fit our needs exactly. If anybody has any suggestions it would be greatly appreciated.
     
  2. Duane P Wetick

    Active Member

    Apr 23, 2009
    408
    19
    I take it that the milemarker Pe3500 is a winch motor? To make it go forward or reverse, a SPDT (single pole double throw) on-off-on 3 position switch is used. Correct? Now this function can be simulated using the supplied solenoid with 2 relays instead of the manual control switch. Now, to make the motor go in either direction, a controller must decide which direction to go, and energize the appropriate relay. Your computer can do this based on the encoder's data. How closely, you can index your table is a function of the winch's minimum resolution. To do this in the real world would require a servo drive and appropriate resolver and controls, which is a little beyond your capabilities.

    Anyway, have fun and I wish you success, DPW
     
  3. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234

    If the carousel was designed in a way to where all the weight of the tools that are on it could rest onto some bearings and have the motor attached via chain or belt drive, if the carousel is built properly, there shouldn't be a reason for your motor to struggle too much and draw that much current when rotating the table....

    Then you could just use an H-Bridge (LMD18200T) to control your motor, this way all you would need from the PC to control the motor would be 3 I/O's, 1 for direction , this would be good to have, then you know which direction it is going when activated,(High goes left, Low goes right, or vise-versa), 1 for PWM (can be just a High with out the PWM, low would turn off motor, although PWM control of the motor would give you more torque, and SPEED control! and you can RAMP the speed up or down.) and 1 I/O for the Brake output...... I suggested the LMD18200T since it has an output you can use to determine motor current draw so you can monitor it if it stalls (which would be wise since you wouldnt want to burn up anything if someone jammed a tool in it wrong and caused a jam. (Murphy's law = if you think it can happen, it will.:)..)) and it can handle voltages up to 55 volts DC upto a maximum of 6 amps max though (but if the carousel is built right, the motor won't even draw that much!).....


    You can go a little further in the design and use the absolute encoder to create a closed loop motor control system, so basically you can have a "servo" you can position and stop at any point....

    My .02
     
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