variable psu from microwave oven power supply?

[Bryant1968]

Got my hands on an old microwave oven(not too big). I'm wondering if there is a way to construct a voltage and amperage variable bench power supply from the parts without commiting gruelsome suicide? Any one have any ideas or schemaic diagrams they would be willing to share with a true hearted hobbyist? Any suggestions would be welcome and appreciated.

 

[Nigel Goodwin]

Got my hands on an old microwave oven(not too big). I'm wondering if there is a way to construct a voltage and amperage variable bench power supply from the parts without commiting gruelsome suicide? Any one have any ideas or schemaic diagrams they would be willing to share with a true hearted hobbyist? Any suggestions would be welcome and appreciated.

The transformers have only two secondary windings, one is about 2000V, the other about 2V (for the magnetron heater). Neither of these are much use, and the first is SERIOUSLY! dangerous.

The only possibility is to rewind the transformer, and this isn't easy as most have the core welded together!.

 

[Bryant1968]

Thanks, Nigel for the info. I was just looking for an easy to con struct bech power supply capable of 5watts at about 30 volts.

 

[Nigel Goodwin]

Thanks, Nigel for the info. I was just looking for an easy to con struct bech power supply capable of 5watts at about 30 volts.

So a 1500W transformer at 2000V isn't much help to you?

BTW, did you mean 5A and not 5W?.

 

[chiba]

You can always rewind the secondaries, i made a spot welder and battery charger this way. Just hacksaw one side off then bang what's left through.I took the shunt plates out and rewound with some heavy gauged insulated wire. There are a few guys who have made welders from these things, ask google he'll know.

 

[Bryant1968]

Actually, until i know a little more about what i'm doing with psu's, I think I'll go ahead and wast some cash at rat shack for a 13.8v 3a fixed. Thanks to you guys for the input and wisdom. Feel free to contact me at bryantndenise@bellsouth.net if you have any decent, asy to manipulate ideas.

 

[stevez]

What will you do with the power supply?

Consider wall warts as a source of lower voltage and make some add-on regulators with things like the LM317 - or fixed regulators like 7805, 7809, 7812 (5,9,12 volts). I've got a couple of wall warts around that are fairly high voltage and power - 18 vdc 500 ma - even a few 24 vac, 1 amp. Takes the more dangerous ac power down to a safer level.

I had to buy some 12 vdc power supplies for my brother. The local electronics supplier had adjustable (steps) supplies good for 2 amps for same price as RS fixed supply. Advantage was voltage could be adjusted, in several steps, down - something like 9 volts, 6 volts - don't recall all the increments.

 

[on1aag]

Why don't you turn it around and connect the secondary to the mains
and see what comes out at the primary ?

on1aag.

 

[audioguru]

A guy made an inverter with a microwave oven transformer and his own secondary winding. It had a very high current without a load. I suspect that the primary doesn't have enough turns to make a high inductance because it is used only intermittently in a microwave oven and its wasted power won't be noticed.

 

[HiTech]

If you're bent on fiddling around with that transformer here are a couple of links for you ... oh and remember at all times that you risk the likelyhood to get killed from electrical shock should you be careless. At the very least, you'd screw up things inside you a good one. Then again folks have survived lightning strikes and walked away relatively ok.

READ THIS INFORMATION FIRST!!

http://www.geocities.com/CapeCanaveral/Lab/5322/mw-xfrmr.htm

http://www.aaroncake.net/circuits/supply4.htm

High Voltage Links

**broken link removed** aluminum can crusher!

http://www.powerlabs.org/igncoildrivers.htm

**broken link removed**

**broken link removed**

**broken link removed**

Spot Welder using an MOT xormer

Build a saturable core reactor for welding.

 

[Hero999]

There are often two transformers in microwaves nowadays. One big one powers the magnetron and another low power transformer powers the microporcessor and associated electronics. The latter might be suitable for building such a power supply, but you might need to add a voltage multiplier to get 30V.

 

[Bryant1968]

Thanx

Hey, thanks alot for all the tips, guys. I got lucky today and found a 9v-30v variable ps for a really good prive. I think I'll put the micro on the back burner.
Sincerely,

Bryant Carter
Tunica, La