Newb question regarding the differences in power supplies

[cptwinder]

I recently started a CNC project as a way of learning something new about electronics, computer programing, etc.

Currently I have a 2 stepper controller using 2 mc3479 chips, and after some extensive research, I followed suite and used the power supply in my PC to make everything work. However, this leads me to my questions, more for my own understanding then anything.

First I tried to use a cheap 12v wall "brick" that I had laying around from some device that I no longer own. When using this, my steppers "giggled" even before plugging the parallel cable into the computer.

Next I tried my huge Pyramid Regulated Power Supply (Model PS-12KX) figuring more amps the better. Well, the steppers didn't "giggle" but they constantly rotated in one direction, again even before plugging the parallel cable into the computer.

Then finally, I ran some leads off the 12v lines from the computer's power supply and all is working as expected.

My question is why? What is different about the computer's power supply's power output? I'm assuming it is cleaner. How does one go about "fixing" one of these other two power supplies so they can work?

Any information will be greatly appreciated.

Thanks in advance,

Jeremy

[pminmo]

Not knowing how you hooked up the chip this is kind of a guess, but I suspect how you handled the gnd/common/0v connection maybe the issue.

[Oldmanandhistoy]

My understanding of suitable power supplies for stepper drives is that an unregulated linear supply is best (please correct me if I am wrong). I have built 4 different linear supplies and have never had a problem with any of them.

By the sounds of things you will know all about linear power supplies so I won’t go on.

EDIT: For anyone reading this that don’t know about linear power supplies please follow this link for some good info http://www.kpsec.freeuk.com/powersup.htm

[cptwinder]

Of course, how could I have missed it? I need an unregulated linear supply!

In all seriousness, thanks for the link, I'll read it in a few.

So am I safe in assuming that a PC power supply is an unregulated linear supply?

Thanks again,

Jeremy

[Oldmanandhistoy]

Originally Posted by cptwinder So am I safe in assuming that a PC power supply is an unregulated linear supply?

No