Longs Motor 4 Axis CNC Kit

So, last night I got a Chinese-looking package from Longs Motor (Hamburg warehouse). The contents were limited to a power supply (24V / 8.3A), four stepper motor drivers (DM420A), four NEMA17 stepper motors 17HS8630N (12V 0.4A 1.8°/step) and a parallel DB25 breakout board.

As expected, no manual, instructions or similar paperwork was supplied. Even the 24V PSU doesn't really match the 12V motors! You can turn it down, but only to around 19V. So I ended up using my 12V power supply for the first tests.

The biggest trouble was making sure everything is hooked up properly. The motors turned out to be 6-wire 2-phase unipolar stepper motors. Each coil has 60 Ohm resistance, with the center connector being half (30 Ohm) against each end. Two of those sets in total.

Dimension drawing and 4-lead vs. 6-lead wiring diagram of the NEMA17 stepper motor

The stepper motor driver can only power two phases (A+ / A- and B+ / B-). I'm still not sure where to connect the coil center to.

Wiring schematic of the CNC kit: power supply, DB25 breakout board, stepper drivers and motors

Finally, the controller board is easy to use if you have a computer with a working parallel port. Unfortunately, my oldest PC is too slow for Mach3 and doesn't have a DVD drive so I could use LinuxCNC, and the next best option lacks the parallel port. A PCIe spare card was recognized, but it doesn't power my controller board as expected. So I ended up using KCAM on my oldest PC for the first initial tests.

Image credits: wiring diagrams by Longs Motor.