DC Motor control

Discussion in 'The Projects Forum' started by Thorp, Dec 4, 2009.

  1. Thorp

    Thread Starter New Member

    Dec 4, 2009

    I need to make a circuit to drive the spindle motor on my cnc mill. I have pieced together a circuit but electronics is not my strong point. I'd appreciate it if you guys could take a look and offer advice. Time is of the essence if Christmas presents are to get made :)

    The motor I am using is a 110 VDC 6 amp .8HP. The cnc control board outputs 0-10V based on the speed specified. Schematic is here:
    http://dl.dropbox.com/u/2399925/Mobile Photo Dec 4, 2009 10 32 24 AM.jpg

    I plan to implement a tach and run closed loop but that can be done later.

  2. Thorp

    Thread Starter New Member

    Dec 4, 2009
    No one?

    What do I need to do to get advice? :)
  3. SgtWookie


    Jul 17, 2007
    Gee, Thorp - sorry.

    You kind of fell under the radar, as there are a lot of people with a lot of projects going on right now.

    The schematic you posted is really dark. That takes extra effort just to get started.

    With 120VAC input across a bridge rectifier, you'll wind up with around 168v DC on the output. Take 120v and divide it by .707107, and you wind up with the peak-peak value. Of course, if you don't use a filter cap, you'll wind up with roughly 118v RMS rippled DC at 120Hz.

    You have a reversing switch shown in your schematic. If you are also going to use an H-bridge, you don't need a reversing switch. If you want to simplify things and just use a reversing switch and a single MOSFET for PWM, that can be done too. Or, if you want to use an H-bridge for PWM speed control and direction, that can also be accomplished.

    It's not far from Xmas. If you want simplicity, better go for the simple reversing switch and a simple PWM circuit. You don't have much time left.