Getting ready to build an OX and trying to figure out the requirements for power supplies. I have some competency with electronics (mostly sensor projects with Arduinos and Raspberry Pis), but this project is well outside my comfort zone. I'm wondering two things (for now): With certain components requiring different voltages, do people run several power supplies? The spindles I'm looking at will take up to 48V while the Arduino and Raspberry Pi in my build will take...a lot less than that. I understand that one can drop the voltage fairly easily. Is that what folk do? Could one not use a PC power supply? It doesn't look like they will do 48V, but 24V looks doable. Something like here? There are certainly a wide range of power supplies that look useable on EBay, but if I can divert something from the waste stream...
I'm not building an OX (I'm trying to work on something that requires no upfront machining), but... I'm planning on using 220V mains to my spindle VFD, 110V to a basic 24V 15-20A PSU for the steppers, and a separate PSU (maybe just a wall-wart type) for whatever computer will be running the machine. This has the primary advantages of a) not overloading a mains circuit due to the heavy spindle requirements (probably less of an issue for you) and b) I can put in a safety switch that both the VFD and the stepper PSU are fed through, but hitting it doesn't kill the computer. Separate circuits are a good thing. ATX PSUs max out at 12V, but they're highly regulated and can push hefty current loads. If you're looking to run 4-5 NEMA 17s, that might work. If you want 24-36V for higher power steppers, then the PC-type PSUs (but not actually ATX) are a better bet.
http://www.reuk.co.uk/LM317-Adjustable-Power-Supply.htm check this website out...the schematic doesn't show transformer,bridge rectifier and capacitors that are all before this circuit but an easy build,all parts can be bought at radio shack.2n3055 transistors need heatsink but osolated from it with pads and thermal grease. Built this supply as a learning project when first getting into hobby. I use this for my benchtop cnc mill that I am currently cutting out my ox plates. I have 4 2n3055 in mine and it puts out 24v 20amps. Hope this helps!
Thanks Rob and SJD. So I'll need a power supply appropriate for the steppers. I may be able to use the same power supply for the spindle (which will likely be about 300W), but should consider a separate power supply. Since I'm working on figuring out the controller, drivers, and steppers as a first step, I'll just need the one for now. (I have no end of power supplies for Arduinos, Raspberry Pis, and random computers.) I'm attracted to the convenience of having a single switch to turn on (assuming the computer is running at all times on its own power), but unless there is an easy way to assure that I don't fry anything in trying to achieve that convenience, I'd better save that project for when I'm more comfortable with the power side of electronics. Then again, there's no reason that I can't do both projects in parallel: Buy two power supplies then work on figuring out how to drop the voltage on the highest voltage power supply down to that required for other components, along with figuring out how to isolate things from one-another. But man, would I ever need some hand-holding.
