Last Updated on the 8th April 07


Building Stepper Drives
My current stepper drives are cheap, nasty and the wiring is styled on a bowl of spaghetti. They are selectable full step or half step, but they lack a PWM Chopper to allow current control of the motor windings. I needed something better . A micro stepping chopper driver will give me more speed and smoother motion. So the search begins...
I came across a website that had an open source stepper driver design (PICStep), exactly what I was looking for. This board is based on a PIC16F628a and a pair of LMD_18245's . You can visit the PICStep website here.
As ever, not wanting to spend more than I had to, I set about devising a plan to produce my own circuit boards. I didn't have a laser printer or the chemicals required to etch the boards, so the toner transfer method was out. I didn't want to pay to have somebody else do the boards for me, so I thought about using the CNC machine with it's current drivers to mill the tracks on the new boards.
This was my first ever attempt at milling a PCB. The idea was to create a toolpath directly from the PICStep PCB artwork, and while not ideal, the resulting toolpath on the screen looked promising. However the milled result was unusable. The traces were thin and broken in places. I needed to come up with a better idea than this.
To maximise the trace area, I decided to redraw the entire circuit by hand in a CAD package. This was both time consuming and tedius. The resulting DXF was used to produce the toolpath. The result was much better this time, and I decided to go with it for the actual boards.
I purchased all the components and eagerly soldered away. Soldering those top link wires can really damage your fingers. Here's the result...... My very first PICStep driver board. Two more of these and an interface board, and I'll be ready to roll.
The Interface board that connects the PC's parallel port to the three stepper drivers was built in the same way as the driver boards. The drilling for all of the boards was also done using my CNC machine. What a time saver that was.
Now that all the circuit boards are built, it's time to build a power supply for them. Buying one off the shelf is to expensive, so it's down to building my own, once again...
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