Power Supply

Thread Starter


Joined Feb 17, 2009
I'm working on a power supply for a 3-axis desktop CNC Mill, powered by 3 stepper motors. I'm having trouble designing the power supply. I need a 24v/3-4A supply.

I was thinking of just using a few filter capacitors after the rectifier but it doesn't feel right. Am I fine? Or is there a better way to regulate the 24v with that high of current?

feel free to ask me any questions to clarify.


Joined May 26, 2009
That's quite a bit of current. You could start by having a transformer that steps the 120V down to 28V. Then you go into a diode bridge which will rectify it. The reason I chose a transformer that steps it down to 28V is because there is a typical 4V drop across all four diodes. Next you go into a filter cap whose value you can determine for 1A of current (if you want more you can have it). That will then go into a voltage regulator and then also some transistors in parallel to make it capable of more current. Since you have 1A, the transistors will add 3A. Or you could have 2A coming in and have the transistors do 2A. It would be better if you had a lower current coming from the filter cap.

Any more questions?


Joined Oct 2, 2009
A filtered, but unregulated supply capable of delivering 24V at 4A will sit at ~30V while lightly loaded. Is that too much variation? If so, then you will need to regulate it.

A better choice would be to look for a ready-made modular power supply on EBay, like this one


Joined Jul 17, 2007
Marlin P. Jones & Associates to the rescue:
24v DC 6.5A switching power supply, $14.95 each. You will be quite hard-pressed to find a better deal on a supply that meets your needs so closely.

I've bought from these folks a number of times. Reasonable prices, and they ship really quickly. They've had this particular supply on sale for a while.