Monday, November 30, 2009

Motor Driver


Motor Driver
Motor Driver

Here's my temporary stepper driver, which I will use until I build a proper one. Some parts of the construction need a working driver, eg putting splines on the shaft for the pinch-wheel extruder, and putting flats or keyways for the axis gears. It doesn't have proper current control, just a resistor, but it should be sufficient for now. I programmed up to 32x microstepping, although steps smaller than about 8x don't seem to have any effect at all - probably because the L293D is only rated to 5khz, but I'm driving it at 62.5khz.

Posted by Triffid Hunter

4 comments:

  1. UnknownDecember 7, 2009 at 9:41 PM

    Hi Triffid,

    nice project! I just stumbled on it on the google reprap pipe. Could you please elaborate on the microstepping schematics? Could you make them available?

    With regards,
    Reinoud

    ReplyDelete
  2. Triffid HunterDecember 9, 2009 at 4:35 PM

    Reinoud, the extruder firmware already does half stepping using the same method I'm using to do microstepping, but check out http://github.com/triffid/ATmega-Skeleton/tree/master/stepper/ if you want the exact code I'm using

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  3. UnknownDecember 10, 2009 at 2:32 AM

    Thanks Triffid,

    i didn't know the `standard' v3 electronics could do up to 64 microstepping steps! I thought it was limited to half-stepping only. This would solve lots of problems for me.

    I am currently building a RepStrapbut i'd like to build an alternative RepRap that'll need the 6400 steps/rotation precision! :-D

    Hmm... you `only' get 8 microsteps effectively? Could the L293D be replaced by a higher frequency rated component? say the LM 18293?

    Also, can the stepper motors currently used in Mendel be used for that amount of microstepping?

    With regards,
    Reinoud

    ReplyDelete
  4. Triffid HunterDecember 10, 2009 at 9:02 AM

    Reinoud, only the extruder can do the fine microstepping because it has an atmega connected to h-bridges rather than a specialised stepper translator like the A3977 or whatever the stepper drivers have. The A4983 does 16x microstep and doesn't need as much tuning, if you're looking for a good translator.

    yes the L293D should be replaced by a higher frequency part. My arduino is generating PWM at 62.5KHz so you need something that handles pwm faster than that.

    I don't think steppers have any choice about being microstepped, any more than dc motors get to choose about being PWMed.

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