Laser Rebuild – Part 2 (control)

I started looking around for a board to replace the original controller electronics.  My priorities:

  • Has to work with EMC2.  That’s actually pretty easy to do since EMC2 is so flexibile, but I was looking for something a little more “off the shelf” compatible.  I’m not afraid to hack on an EMC2 configuration, but it’s not my strong suite and I want easy.
  • Besides driving the steppers and laser, it needs to handle as much of the other stuff as possible.  Door switches, cooling pump, air assist, etc.
  • At least 1/8 microstepping.
  • Needs to fit in the cabinet along with a power supply and any fan, wiring, etc.
  • Not too expensive.
Also, it would be nice if it supported some direct control so I don’t have to do everything from the PC.
I found a few solutions that were interesting but once again, the Buildlog guys seem to have anticipated my needs perfectly.  The laser interface driver uses pololu drivers which I’m familiar with from my Reprap RAMPS board.  The pololu stepper drivers are on a separate little board so they can be replaced easily if something “unexpected” happens.  Most of all, I’m happy to see an active community of guys using this hardware in conjunction with EMC2 to drive a laser.
The board is set up to control 3 Axis.  My Z axis is manual, so I have one driver free.  I’ll either convert Z at a later date or maybe think about something like the rotational engraver on this page.
Here’s what the stock cabinet looked like:
After gutting it I had a few leftover parts:
After mounting the new controller, it looks like this:
The three black posts are stand-offs for the top panel.  The new controller supports some manual control, so I’ll build a new panel to go there.
The DB-25 connector and the pololu microstepping controls fit almost perfectly into the existing holes in the chassis.  To make it fit, though, the mounting holes on the right edge of the board were under the lip of the right sidewall.  I couldn’t drill and tap under there so I had a to make a small acrylic part.  The controller is mounted to the acrylic on that edge and the acrylic is screwed into the original holes.
I already had a 24V power supply salvaged from a printer and it fit nicely in the back.  The filter, relay and chocolate-block terminal strip are the only things I saved.
After wiring it up and hacking up a configuration in EMC2, I have it moving the X and Y axis, detecting the limit switches, and detecting the safety switches on the doors.  It should also be tripping the relay, but I think the relay may be bad.
I don’t have any documentation on the number of steps per inch for the axis.  I emailed one of the guys from and he got me very close.  Theirs runs 500 half/steps per inch. I’m going to run everything in metric so I converted. Then I clamped a digital caliper and started fine tuning by trial and error. I found a value of X steps per mm got me within 9 one-hundredths of a mm over a 100 mm travel. Not bad.


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