[Trentec]

I have a couple of options to choose from and was hoping someone could help me choose the best of the two. I have read the switchers are not "ideal" for stepper drivers but I have these IOTA DLS-30 units available (12V 30A, Ripple and Noise = <50 mV rms) I know 30A is overkill and series wiring may work isolating one of the chassis grounds. But is not something I am comfortable with as these are not dirt cheap units. The second is two old battery charger transformers 12V 6A and from what I have read this would be a better option. Ok heres the but, they seem to have a center tap with one diode (half wave I assume) and I need to know if in series how these diodes will affect the output and where to place the other two diodes or can I just put the outputs through a full wave Br Rec I have already? I would love to just get rid of the existing diodes so this would be easier for me to understand if thats possible can I just jumper where the diode is and remove it?

Also if it matters I plan on using the Zylotek drives and motors. Because as much as I would love to try and build my own drivers overall success is something I would like to achieve with as little singed hair as possible!

Thanks in advance

[NC Cams]

Read the following first:

Daisychaining ATX power supplies:

http://www.cnczone.com/forums/showth...015#post142015

http://forums.bit-tech.net/showthread.php?t=108208

Linear P/S design/construction
http://www.campbelldesigns.com/files...ply-part-1.pdf

How to properly phase a transformer in linear p/s:
http://cnczone.com/forums/showthread.php?t=14821&page1

Servo amp P/S design
http://www.elecdesign.com/Articles/A...7635/7635.html

Servo motor , servo amp, powersupply sizing for CNC
http://www.rutex.com/pdf/Mystique2.pdf

[Al_The_Man]

What you need to figure out is what the transformer has for secondary outputs (AC) , measure the outer ends and to centre tap, ignore the rectifier for now or remove it.
And then we can advise from there.
Al.

[Trentec]

I will wire one of these after work tonight and measure the outputs until then I can tell you that they are still wired in the chargers and the outputs are as follows, the far left (single coil lead) gives 6V 2A the center tap is common, second to left and first right of center gives 12V 2A and the right of center alone is 12V 6A what appeared to be a fourth tap is just the other end of the resister or diode hard to tell because it is wrapped in the insulation. The other odd thing is that it has three inputs the first ac input goes to a breaker then to a shunt the two black trans leads are connected to the shunt. The other ac lead goes through the ammeter then to the white lead of the transformer. I thought the shunt was for the ammeter but now Im confused.

1 2 3 4 5
6V2A 12V 2A 12V 6A common
single Double connected to double
coil lead coil 5 via diode or coil lead
lead resistor common
to all outputs
(single coil lead)

I also have a much simpler 12V 15 A transformer and I think I can get another. The reason I wanted to use the ones above is because I have seven of them all identical so replacement parts would be on hand.

[Trentec]

sorry the above needs correction terminals as listed give the rated voltage with the common they are not combined. sorry the switch was mis-leading. I promise not to post any more replies until I am wide awake!

[Trentec]

eek the diagram above got condensed and is now useless so I will give my latest revelation the outputs are inputs and the inputs are outputs...lol all the leads were cut off long ago for use as 12V power supplys by someone else. Although the DC ammeter on the AC side and the green ground wire running down the middle of my po neg leads should have been a clue!! Dont worry this is why I poke prod and ask questions before adding AC...! but this does place the unknown resistor or diode on the input side and the shunt on the output side still not feeding the ammeter. :idea: Can I just leave them wired as is switch selectable and all (in series) by-pass the shunts and use my Bridge rectifier giving 24V 6A? or do I have to use the 24 X 1.4 =33.6 to determine the voltage in this case? and yes the power supply provided by the vendor is looking cheaper by the minute.

[Al_The_Man]

Not really sure what you have there!
Once you rectify and add capacitors, you have to apply the 1.414 multiplier to the AC.
Al.

[Trentec]

Hope these help.

[Al_The_Man]

Still not clear on the secondary side, I suggest pulling the leads off the secondary and measuring resistance to see how many windings and what is centre tapped etc, also do a A AC voltage check when unconnected, did you identify the device in the lower right with the three transformer leads on? rectifiers ? Or is that the range switch?
Al.

[NC Cams]

Trentec = you have a multipurposed tranformer that shares a common core with multimle secondary windings. Via this design, they effectively generate multiple voltages with distinctly different current capacities from a common set of primary windings.

Although you can start to rehook the secondaries up in series to gain higher voltage, you're still goint to be limited to the current output of the LOWEST current capacity secondary winding once you hook them together.

If you have multiple idential transformers, I'd consider hooking up the high current simillar windings in series to gain the higher voltage you need. Hooking up the 12 amp phase to a 2 amp phase to get the desired total voltage is NOT adviseable.

Better yet, you really should draw up a schematic ala what Jerry the Fly Guy did. He learned a lot from doing it. It is simply FAR TOO EASY to get confused by simply hooking up wires, expecially if you don't have a logical plan/schematic to follow. To do the schamtic, you'll have to draw up a transformer. Once you "see" how the windings work and trace them out with a VOM, it is much easier to figure out what needs to be hooked where.

[Al_The_Man]

I think I may have interpreted wrong, I took it the RH side was the secondary, but looking again it could be the primary?
If this is correct then you have a full wave centre tapped supply.
I think you need to add a bit more info!!
Al.

[Trentec]

The seletor switch is on the right and the shunt\breaker is on the left. I am still not 100% positive about which side is the primary input my suspision is that the AC input is on the right side and the shunt is used for rectification if so I can easily series these without rewiring. I also have a larger simpler 12V 15A two inny two outy and I can aquire another, would 15A be too much with proper fusing? I also read that I cannot get a correct reading of the outputs with an ordinary multi-meter is this true and if so how do I measure? I have decided to purchase the power supply for the steppers from the vendor because frankly as you can tell I'm dangerous with electronics! But this is not in vain as I am going to build this supply for learning purposes and your input is greatly appreciated I have some work to do getting the measurements suggested and I will get some pics of the larger transformers.

Thanks again

[Al_The_Man]

You can read the AC with an ordinary meter, I am pretty sure that what you have is the secondary on the left and it looks like two rectifiers with centre tapped secondary, the output of the two rectifiers goes to what appears to be either a shunt or a circuit breaker and then out.
Al.

[Trentec]

Ok here are the AC and DC voltages from the charger transformer (no cap I am assuming is why I could read the DCV) the right side is the primary side (flame2). Using the selector, on the 12V 6A setting there is 13.2V ac and 12.32V dc on 12V 2A there is 11.4 ac and 10.64 dc and just to be thorough the 6V 6A gives 8.12 AC and 7.6V dc. Using a continuity test all primary windings are connected.....? Though it still works so again I have to assume some of the tests were T.C.O. (too complex for operator)! So as not to confuse everything I will make another post with the pic and results from the big transformer.

[Trentec]

Then I hooked up the big one and measured before the shunts and resistor? and got 28.7V ac and 13.3VDC unfiltered the white lead bottom center secondary side. the resistor component bridging the gap between the rectifiers shunts or magic dc things...lol is 47K 250V. This looked promising until I figured the 1.4 multiplier and looked at the 35V max on the Zylotex driver (with bemf) this would give around 40V correct?

[Trentec]

Thanks for the help to this point Al and Nc. I am going to series the larger transformers to run a 120V dc motor to run a makeshift lathe to turn my acme screws and the little ones will become useful for a Nema 17 dremel version I want to build later. I am on to linear bearings!

The experimental power supply is shelved because it is only the addition of the filter capacitor to complete it and the voltage would be too high with the later tformer (for the driver) and the smaller ones have the same problem in series so the little six amp 12V should make a nice supply for 17s. Thanks again between the recomended reading and your posts I think I have a good enough understanding and the formulas for the rest.

[Trentec]

I thought I would share what I have learned thus far. The rectifier circuit for both transformers is a "full wave center tap" as Al said, and requires that the transformer be approx 30% higher in its power specs than if using a "full wave Bridge" because only one coil is used at a time. This explains the odd readings on the multi-meter of 28.8Vac so I have to assume that my transformer is closer to 20% over for my rectifier. So I have a 24-0-24 on steroids. The yellow component turned out to be a film capacitor I dont know what its purpose is but it is wired on the ac side of the rectifier. Al you had it right on the money the rectifiers are tied to a metal bracket by a copper strip and flow into a circuit breaker. NC I am learning how to draw it out now and for some reason my ohm meter read 0 on the transformer but I have a cheap meter I sold my Fluke years ago when I stopped fixing cars for a living a lesson I have since learned never sell tools! I would like to contribute a site to the list you gave me it was also very helpful. Thanks again.

http://sound.westhost.com/xfmr.htm

http://sound.westhost.com/power-supplies.htm