Last time I tried to build a CNC, I didn’t realise how CAM software interacted with the hardware. From research I have found that packages like Mach3 generally communicate with a CNC tool via a parallel/printer port. The protocol is pretty simple: each motor has two direct pin connections – step and direction.
So first things first I need a parallel port. You don’t find these kind of things on modern laptops, so I took a dive back in time to my dad’s old laptop from about 10 years ago. We are talking a 256MB of RAM, 20GB HDD, 1GHz pentium processor, 3.37kg beast.
The first step I decided was to check that the parallel port is spouting out the right kind of data. So with the help of a parallel port break-out device (thanks again, dad) I hooked up the PC to my oscilloscope.
What I would expect is a series of pulses on the “step” pins and a constant voltage (until I change direction) on the “direction” pins. Luckily, this is exactly what I got.
What this means is that the PC can be connected directly to stepper motor controllers which coincidentally also have a “step” and a “direction” pin and therefore I do not need any kind of intelligence in the form of a microprocessor.
In the end the stepper motor drivers I went for are these albeit from a significantly cheaper distributor:
So, next thing I reckon is to wire up one of these drivers and motors and test it out.