CNC controller, check my thinking please?

Discussion in 'The Projects Forum' started by awhaley, Dec 22, 2011.

  1. awhaley

    Thread Starter New Member

    Dec 31, 2008
    4
    0
    I'm cross posting this from cnczone... because after I posted it there I realized this might be a better place to post my electronics questions.

    I'm working on my first cnc machine- it's going to be a fairly simple 3 axis, dremel based, drawer glide and threaded rod drive contraption... and I'm feeling good about the hardware as there are a so many great hardware writeups out there... The software side however, I'm finding a lot less info about. So I'm going to post what I THINK I've figured out... and hope someone smarter than me can tell me what I've got wrong.

    From what I see in Mach3 (computer software for CNC machine control) , it appears that side of things is reasonably simple - it's going to control the parallel port... specifically 6 pins of it - one direction and one pulse pin for each axis. I'll tell Mach3 how many degrees happen per step, and what linear distance is moved by each revolution...

    Then I'm going to feed those six pins into an arduino (I'll be using the analog pins, but configuring them as digital inputs, and eventually I'll remove the arduino and just go to a atmega328p with bare minimum support components... and really nice filter caps...)

    The arduino is going to use 12 of the digital output pins to drive 3 L293D driver chips. Each time a pulse is detected on one of the pulse inputs, the arduino will check the state of the direction pin, and either step forward or backward in the stepper position lookup table accordingly.

    The 293d chips will be hooked directly to 3 small bipolar steppers, which will be hooked direct drive to the screw drives on the machine.

    Will all of that work to interface Mach3 to the steppers? Is there an easier way? Does a plugin or driver exist (or could it exist?) to allow me to skip the arduino and use the parallel port directly to control the 12 pins that feed into the L293D drivers?

    And one sort of related question... Mouser carries the L293D for 4 bucksish, and the l293DNE for closer to 2... Is the NE part acceptable, or is there a reason to spend the extra few dollars for the plain D model? I read the datasheet and couldn't figure out what the difference was between the D and the DNE...

    Thanks in advance for answering some newbish questions!

    Art
     
  2. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,013
    1,531
    Really, make it easier on yourself and just buy one of the Gecko drives. CNC is hard enough with out trying to come up with your own drive hard ware. After spending much time on trying to DIY, that is what most people end up doing.:)

    Stay away from the TB6560 drivers. The chips are hard to initiate correctly and most of the boards end up having to be reworked. Check the treads on the Zone.
     
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