Microwave transformer built power supply

[Pythagoras]

Hey Bubba, You should cut and paste that and repost it in a tutorial section of this forum. We need references like that. Most posts just dissapear away never to be seen again. Please preserve this post. Thanks

[Bubba]

Ok, will see what we can do. May edit it a little to remove references to this thread etc and put it up there.

[Dylwad]

Got my 80v 47000uF capacitor installed today.

53 Vdc no load
38 Vdc @ 9 amp draw

Transformer never got above 120*F

This gives me 23X motors rated voltage at no load and about 17X at full load.

Total cost is still under $30

I kept wandering around the garage looking for something that would pull around 10 amps. Turns out about 1000 feet of 16 gauge wire is about 4 Ohms.

Ill post some pics when i finish it.

Thanks for the info,

Dylan

[TinkerDJ]

What did the cap cost you and were did you get one. I'm having a problem finding one that is not way to expensive. Thanks.

[Dylwad]

Found it on Ebay. $16 shipped.


Dylan

[TinkerDJ]

Houston we have a problem.

Guess what i did when i was drilling the high voltage wires off my microwave transformer. I nicked a wire on the 120volt coil DOOOOOOOOOHHHHH.

Is there anyhope?


All that work to neatly cut off all the wires and not nick the core or hit anything and when its all clean; there's this little copper spot gleaming like a small warm sun, burning my eyes as i look at it.

[Bubba]

Dave,
IT MIGHT BE POSSIBLE to salvage the situation.
1) use a glass and verify that only ONE wire is knicked
2) if so, you might be able to put some insulating varnish or paint on the offending spot.

Best advise is to find another transformer if you can though.

[TinkerDJ]

Cool i'll varnish it then power the coil and see if it shorts. If not how much wire do you think i will have to use for the line side of the transformer.

[Bubba]

Dave,
I haven't unwound on to see!
Also, I haven't done any calculations like this in YEARS to even estimate this.

[lerman]

Cool i'll varnish it then power the coil and see if it shorts. If not how much wire do you think i will have to use for the line side of the transformer.

That should be easy to determine. How many turns did you put on the secondary? How many volts was it? The number of volts per turn for the primary will be the same as the number of volts per turn for the secondary. So if the secondary was 50 volts and required 100 turns, that is .5 volts per turn. If the primary is 120 volts, then 120/.5 = 240 is the number of turns required.

You might try unwinding the primary until you get to the nicked part, you might discover that you've only removed a relatively small number of turns. In that case, you can just cut off that length of wire and throw it away. (Make sure you adjust the number of turns on the secondary to match.)

One problem with winding your own transformer is that it is hard to wind it evenly. That makes it hard to get as much wire into the core as the manufacturer did.

Ken

[TinkerDJ]

I nicked the wire right in the middle. I'm going to wire the secondary and then test it out. As well i was going to look into building a 110 to 220volt step up trans for use with a vac pump i have. But for now i hope i can get this one working. I've located a bridge and cap for it so things may work out.

[TinkerDJ]

Okay i got 1 pound of #15 wire from the local motor winding shop. Its the biggest he had with out selling me a whole roll. Wish me luck.

[TinkerDJ]

Well i put 40 feet of wire on the transformer coil and got 60 volts. So i took off 25 feet of wire. Allways start small and work from there. Tested the voltage 25 volts. Which should be 36dc when its put through the diodes right. Or am i wrong. Anyways i hooked a 100watt light bulb to the sec, hooked my amp meter on the wires to the pri, and my heat sensor on the top of the transformer. 4 amps, for 4 hours made 140 degrees F. I hope this is enough. Now in one of the other posts there was a listing that i could as well put a 5 volt coil on for my low voltage. Now is this a tap or is it a whole coil on its own?

[Al_The_Man]

If you are going to connect up the DC commons then you would have to make it a separate winding.
Al

[ViperTX]

Yes. multiply the secondary AC volts by 1.4 to get the secondary DC voltage then subtract 2 diode drops or about 1.4 VDC....and you have your power supply's output at the capacitor.

[joecnc2006]

Is there a picture tuturial anyone know of to make the microwave trans, this would help me tremendously.

thanks, joe

[Bubba]

Paul was nice enough to put up the writeup that I did at the following link:

http://www.cnczone.com/modules.php?n...warticle&id=27

Enjoy

[smarbaga]

i have an earlier post ' hot transformer '
i tried 2 different manufacturers of microwave transformers with no secondary on them and they both drew over 12 amps on the primary.
i would say they ran 200 deg far.
there is another micro down the street. i guess i will go and snag it and give this one more try.
the transf's i used were from newer micro's say 5 years old or less.
the micro down the street is an older guy.
by the way .... i am a transdormer freak . i have had skids of them ...
scraped them for the weight ( way back when the switchers came out)

[Xterrian]

Well, I've been putting off buying a 24 volt 15 amp power supply. The next door neighbor threw out his old microwave so I grabbed it up. I managed to pull out the transformer without killing myself (I've worked around High Voltage before, but the mention of the professor earlier in this post had me nervous). I have a healthy respect for electricity, but I still want to try this modification. I am willing to take pictures for a step by step tutorial as I do this. Would anyone be willing to talk me through it again one step at a time and I'll take pictures to go along with the thread? I read the instructions several times, but still have questions. First, I'm not sure if this thing is powerful enough to give me 15 amps at 24 volts. I don't know the wattage of the microwave. It was small so maybe this transformer won't be big enough. Second, I'm not sure which winding is the high voltage one. Should have paid more attention when I pulled it out. I'm pretty sure it's the one with two connectors, but want to be sure. It has the welds on the sides that were mentioned earlier. I will post my first picture tomorrow. By the way, there was an envelope inside of the chasis with schematics, test procedures, wiring diagram etc. Should I post a scan of the paperwork along with the picture? I got a bunch of switches from the door interlock and timer as well. One man's junk is another man's part's store
Thanks in advance for any help with this project!
Randall

[Imagineering]

XTerrian,
Have a look at this Site which outlines the building of a Spotwelder using a Microwave Transformer. It has a few photos which may be of some help.
I spotted a few other Microwave/Spotwelder pages on the 'Net which may be of help, so just do a Google search using Microwave and Spotwelder as a keywords.

http://www.rhunt.f9.co.uk/Electronic...lder_Page1.htm