Linear power supply...

[WilliamD]

I'm finishing up my power supply, and had a couple questions. I took the transformer out of a 1400 watt microwave, and I believe it's rated at 13 amps. So that covers the 10 amps I need. The other side of coils is wound up a bunch, so I would think that it's putting out a lot of current, but when I test it with the volt meter, it doesn't get a reading. Do I have to have the bridge rectifier hooked up to get a reading? Am I required to have the Capacitor hooked up to get a solid reading? What are these items for? I have a large capacitor on the way, and I have the bridge rectifier. Should I just drill out the coils and wind them up myself? The ones there are probably too much, taking into account what I've seen from Joe2000's transformer setup. Any help or links or input would be greatly appreciated!

[whateg01]

WilliamD,

The voltage coming off of a transformer will be AC. You should be able to set the voltmeter to measure AC Volts(RMS).

You could also connect the rectifier and measure the DC voltage across the +/- terminals. There is going to be some ripple there, but you can get an idea of what voltage is present.

Dave

[Mcgyver]

search around this site, Bubba has a great tut on rewinding transformers. what do you mean wound up a bunch? A transformer in a microwave is step up - the secondary produces a much higher voltage than the primary, you have to removed the secondary and rewind with the right gauge of wire the right number of turns to get the voltage you want

[WilliamD]

Thanks for the replies guys. So if I understand this correctly, the volts coming directly off the transformer are still AC, the bridge rectifier tuns them into DC? If that is the case, that is the piece that I'm missing. On my bridge rectifier, it has four poles, one marked with a -, one with a +, and the other two with ~. Which ones do the transformer wires go too? I'm thinking it's to the ~'s. As for the cap, is that just to clean up the power, or does it have to store the power to put it out first? I'm an electronics novice, so sorry for all the questions. Bubba does have an excellent write-up for the microwave transformers!

[CLaNZeR]

Hi WilliamD

Yep AC into your transformer and AC out hopefully at a reduced voltage!

Then pop it through a bridge rectifier that will get you your DC line. Make sure it is rated for the voltage you are pumping into it and the current you want to pull.

The ~ are for the AC output lines from your transformer and the + - are your DC out.

The Bridge will lift the voltage so be aware of this and meter out DC side.

Then smooth with your Cap and use DC voltage Regs to get the correct voltage needed and again also ones to match the current ya need to pull.

Regards

Sean.

[WilliamD]

Thanks again, my next few experiments should be much more successful! I have a treadmill motor to power with a big transformer I got, so I'm hoping that I can just use it as is. It looks like I have to order the high amp and volt bridge rectifiers online, Radio Shack only has small ones. Looks like I'll also have to order a big capacitor online also.