January 29

DIY CNC Part 6: Wiring the Power Supply


In this part of the build I used a computer power supply to provide the necessary power to the stepper motor drivers and motors.  Finding a computer power supply wasn’t a hard task as I had three old computers in the attic.  I removed a power supply from one of the computers and made a few modifications to the power supply so I could use it to provide power to the stepper motors and drive the stepper motor driver modules.

tangouniformGenerally, an ATX power supply is usually turned on and off by the computer, but for my operation I need the power on and off when I flick on the power strip.  To achieve this, a minor modification is required to the main group of wires.  To make the power supply useful in this application, I took the green wire and connected to a black wire.  It isn’t like defusing a bomb but it is easy as eating pie.  This mod and I have done several times to use the power supply for powering up my lipo battery chargers.

powersupply1Once the power supply was modified I took all the yellow, red, and black wires out of the wire bundle and hooked them up to the stepper motor driver boards.  The boards will provide the signal pulses to the stepper motors.  From the power supply, I used some twisted pair I had to make the connections to the parallel port.  Twisted pair is generally used for telephone/data so it should do just fine for this application.


On the other end of the twisted pair was a 25 pin connecter which will plug into the parallel port of the computer.  The pin out was wired according to the build plans.


With all the wiring just about done it was time to figure out the computer part of the equation.  Although having to purchase a PCI card was not in the game plan, I had no choice but to purchase the card or this project would be dead in the water.  The computer I chose to use for this build did not have a parallel port so it was a necessity. Most computers today have USB ports and it can be challenging to find a computer with a parallel port.   Parallel ports are old school, but I managed to find a compatible card at Frys.

PCIcardWith the card installed, I completed the final assembly of the CNC machine by installing the anti-backlash mechanisms on all three axis.  The anti-backlash provides the driving mechanism for the stepper motors to transport the carriages.

Anti-backlash installed on all three axis.

With the table built, wired, and a computer ready for the CNC machining software it was time to bring it inside and begin the computer adventure.  In the next post, I will go over the software I chose to use on this build.

Until then,

Happy Building!



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Posted January 29, 2014 by DIY in category "CNC", "DIY