Loading ...
Sorry, an error occurred while loading the content.

H-bridges

Expand Messages
  • Alan King
    Just uploaded a pic of the $2.75 bipolar steppers and the H-bridges I m working on to run them. Less than $5 per motor/driver combo total. The two 4 mosfet
    Message 1 of 2 , Oct 2, 2001
    • 0 Attachment
      Just uploaded a pic of the $2.75 bipolar steppers and the H-bridges
      I'm working on to run them. Less than $5 per motor/driver combo total.
      The two 4 mosfet H-bridges are obvious enough, the middle IC is a 7406
      OC inverter to run the higher voltage to the gates, and the rear IC is a
      4069, using two gates as an RC oscillator, and using the output of that
      and two diodes and caps for a charge pump that makes 8V or so. Needs
      another stage or so on the charge pump since the 8V isn't high enough to
      turn the high side fets completely on, but they can handle the extra
      drop fine for testing. Knob to the left is a mechanical encoder to the
      7406, turn the knob and the motor spins, easy enough to hook it up to my
      pics later. Probably going to put in a sense resistor, and a small pic
      to control the transistors seperately and sense the current, and make it
      a chopper drive controller.

      Notes:

      Bipolar steppers are nice, that extra 30% or so of torque really adds a
      lot. These are rated at 70 oz inches holding, and still have 20 oz
      inches at 10k steps/sec, or 50 revs in a second. Can't wait to hook up
      a 16f877 and see that happen, never seen a stepper go that fast without
      skipping. 50 spins in a second is going to be blindingly fast compared
      to the other steppers I've run, probably never gotten any other steppers
      past 5 or 10 revs per second without skipping..

      When I was asking about cheap transistors, never did get much response.
      I was looking at 8 or 9 cent to-92 types, and run the motors a bit under
      their max current. Ended up I got 12A 55V .08 Ohm mosfets for around 5
      cents each instead after bargain hunting. And they won't get hot even
      without a heatsink while running most steppers.
    • Alan King
      ... Well first question is how many wires does your stepper have? If it has the more common 5 or 6 wires, you can use a much simpler circuit than what I m
      Message 2 of 2 , Oct 2, 2001
      • 0 Attachment
        Raistlin Majere wrote:
        >
        > great setup. how are you stepping your motor? Can you help me with my
        > stepper motor? I think i would like to drive it using an h-bridge but i
        > am not really sure how that would be accomplished. it looks like you
        > have it working
        >


        Well first question is how many wires does your stepper have? If it
        has the more common 5 or 6 wires, you can use a much simpler circuit
        than what I'm doing to drive it. You only have to have a dual H-bridge
        driver if it's a 4 wire bipolar motor, the only reason I've done it is
        because I got 50 of these motors at low cost, so it was worth getting
        all of them and building the driver circuit around them. For just one
        or a few you're as well off to use the other motors and the easier
        driver circuit, unless you just happen to already have some 4 wire
        bipolar motors laying around. Even if you've got a bipolar motor or
        two, I'd still pretty much recommend getting a 5 or 6 wire one, trying
        that first, then learn the H-Bridge type afterwards. Much better to
        start simple first and get a feel for it, then work with the more
        complex types..

        Alan
      Your message has been successfully submitted and would be delivered to recipients shortly.