Home Made "Junk Box" Power Supply

[emtffkev]

I am in the process of building my cnc mini mill, and I am trying to do as much of it from scratch as I can. I have the entire machine built. I scrapped some 100 oz/in steppers from printers. I am in the process right now of building my controller/interface board.

I am looking to find a way for a beginner to make me a power supply for my unit. I would like to make this from scrap stuff I have laying around or things I can find cheap or free around my community. I have an old refrigerator and I'm not sure if I can rework the power supply for it to work with my machine. I am trying to make the entire process of this a learning experience and would like to set this up from scratch.

This community is the best out there and i'm confident that I can find some help amongst the Guru's here

Thanks
-Kevin

[vger]

Yeah ! Another real DIY'r
If you are building from scratch (where do you get scratch anyway) you will most likely be building a "linear" supply, that is it will not be a switcher. I'm not sure what power supply a refridgerator would have that would be of use unless it's one of those "solid state" refridgerators that use the peltier junction heat transfer pumps.

Here are a couple of links that may help.
http://ludens.cl/Electron/Ps20/Ps20.html
http://www.reconnsworld.com/power.html

If there are any "computer recycler" places in your area, you might want to give em a try and ask if they have any really old big printers you could rob some parts out of. Transformers, capacitors, full wave bridges, and maybe even some bigger steppers.

Enjoy
Steve

[emtffkev]

So how do i know what size PSU I need for my machine?

[LeeWay]

It is mainly dependent on your stepper drivers first and then the motors. The motors can probably handle a lot more volts than you might think. With Gecko drives, you need anywhere from 4 times to 20 times the rated motor voltage. Amps are also a factor for both the drives and the motors. What type drivers are you using? I think if they are from the printer, they may be on the small side. It also depends on what type of machine you want to make, but a mill will require a pretty good drive and as beefy a set of motors as possible. The 100's may work okay if the rest of the machine is first rate. Using less than optimal screws and bearings will reduce the effectiveness and strength of the motors.
A few more details from you and these guys will be able to home in on exactly what you might need and may be able to expect.

[emtffkev]

Well my machine is fairly small.

The drivers I am using are from PMinMO.com. This one.

This is a link to my machine, I haven't measured exact cutting area yet, but I get about 12x12x3. I am using it for some wood and plastics as well as engraving and PCB boards. This is a learning machine for my bigger one that I will be building in a couple months.

[emtffkev]

Would this power supply suffice for my needs.

My steppers are 4.1v and 1.1a. I am running a 3 axis machine.

Also if someone can look at that PS and tell me if I am correct. According to the creator if you use a LM338 instead of an LM317 I can have it be a 5a PSU?

[FPV_GTp]

hi

Some very nice information here guys

keep up the good work

cheers

[LeeWay]

Originally Posted by emtffkev Would this power supply suffice for my needs. My steppers are 4.1v and 1.1a. I am running a 3 axis machine. Also if someone can look at that PS and tell me if I am correct. According to the creator if you use a LM338 instead of an LM317 I can have it be a 5a PSU?

That was my take as well about the 5A. It looks like a nice little project to make that, but is appears to be very similar to a standard battery charger. For that voltage and low amperage, there are plenty of cheap supplies already made. Check Ebay. Once installed, you won't have to adjust your power, so the guages aren't really needed, but nice to have. I am not familiar with those drives, but I would think this size supply would run the 100 oz motors.
Just an FYI.
I am using a Lab supply with my plasma. It has digital readout, but I will be running it in series to get 62 volts with 6 amps. My motors are 2.8 amp 425 oz so this PS won't supply the full current need for all three motors at the same time, but since it's plasma, the Z motor won't be doing much. That should give the extra amps to the X and Y motors when they both move together.
My router has a 28 volt 10 amp linear supply which works well with the 3 axis Xylotex and 270 oz motors.

[sawmiller]

heres some pic's of my mill. it uses the PMinmo drivers, and 3 computer power supplys, 2 at 12v and one at 5 volt in series to give me 29 volts , drives my 126 oz/inch steppers at 25 ipm no problem ( parallel bipolar )
just make sure only one power supply has a ground to the case...
btw i still have to stuff those power supplys in a box. hmmm maybe i'll carve a wooden one
dan

lurker coming out... my rig

[emtffkev]

Only reason I am avoiding purchasing an already built one is that I want to use this to learn more about them. I'd rather build one from scratch. I have a bunch of transformers and caps and stuff I've scrapped from other electronics I'd like to put together and make a functional PSU even if it is low powered just to learn about it for now.

[emtffkev]

To give more specifics of the transformers I have on hand.

1) Han Young Electronics Model # HY-8503
Input: 120V 60HZ 1.6A
Output: 29VAC 1.6A
8.3VAC 2.5A

2) Basler Elictric Model # ???
Input: 120V 60HZ 1A
Output: 28.1V 2.2A
8.5V 2.7A

3) IBM PN # 6185861
Unable to find specs on this particular unit.

All units have the typical 3 prong computer power cable input with a on/off switch attached to the unit. They all have a wiring harness coming off of them with 4 wires attached to the harness.

I've also got a bunch of capacitors and all sorts of stuff I can probably put together to get a functional, albeit primitive, PSU working.

[LeeWay]

Looks like that site has the plans mapped out pretty well. I say go for it. Many guys here build their own PS. Most of the are toroidal I think. Most are also much more power and perhaps a little more cost. Nothing at all wrong with building one, especially since you have some of the parts on hand. Some guys do electronic work out of love, but I do only as a necessity.
I blew out my first Xylotex with a short to ground on one motor from a rush to test. Didn't tape up an extra wire. I had cut it off flush, but it hit the case perfectly.
So, make sure you do the testing the designer suggests.
I had such a sinking feeling when this blew. I want to help you avoid that feeling at all cost.
Xylotex was great about repairing the board though.
Good luck with it and let us know how it goes.