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Friday, August 10, 2012

3-Axis CNC Controller

In a previous post, I showed the single axis stepper driver boards that I sent out to be made by OSH Park. These seemed to be electrically fine, although it was tricky to properly test without the connectors and other components.  After a quick order from DigiKey, I had the bits I needed.


I'm pleased to say that these work as expected, allowing the microstep mode to be chosen by DIP switch, breaking out all inputs and outputs with screw terminals, and providing the connections needed for high and low limit switches.  I've assembled three of these and screwed them to a piece of MDF to serve as the basis for a 3-Axis CNC controller board based on an Arduino Uno and GRBL.






The start of this board is shown above. Before it's complete I need to add the power connections for the high-power side, along with the limit switches.  I have the GRBL firmware flashed onto the Arduino and have connected a few motors to this setup and everything works great!


Shown below is a closeup of the boards.  The screw terminals in the front connect the limit switches for the high and low endstops.  These have pulldown resistors and are connected to two of the screw-terminal positions on the logic side of the board (the two un-wired stops).  The remaining pulldown resistors are connected to the microstep selection pins, which are set by the red DIP switch.  On the right side of the board are the motor connections (the 4-position terminal block) and the motor power connections (the two position terminals).  All connections are with 3.5mm terminal blocks, which actually meet the power requirements for multi-amp 24V operation.  They also allow multiple connections to be made which allows the daisy-chain type wiring shown above.  The low-power side also has these connections since even though they are not needed it's nice to only need one screwdriver to do the wiring.

I'm quite pleased with my first attempt at getting a board made.  It worked first try, the quality of the boards is excellent and I think these drivers can form the basis of a good many other projects.

3 comments:

Arun said...

Hey James, enjoyed reading through your CNC project. Would you be able to release the eagle files for the stepper driver boards you designed?

James Gregson said...

Sure thing, the Eagle files can be downloaded from the following link:

http://sites.google.com/site/jamesgregson/tmp/single_axis_breakout.zip

This version fixes the silkscreen error from the previous one. I used 10k resistors for the pullups.

I think pretty much any diode will work for the reverse polarity protection on the logic levels. Note there is no reverse polarity protection on the motor supply.

Hope this is helpful!

James

Shahabz Hussain said...

arduino code plzzz