2263 - 10 Things To Do With A Microwave Oven Transformer

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this is basically a reposting as the other version got lost somehow

[lloydevans]

For the battery charger idea, if the intention is to charge car batteries (or any other 6-cell, 12 volt lead-acid battery), winding enough turns to get 12 volts DC out isn't quite enough, because when fully charged, a lead-acid battery should give between 2.2 and 2.4 volts per cell - if it's a brand new battery, it is likely to be at the upper end of that range, if it has been used for a few years and gone through a few thousand charge-discharge cycles, it is likely to be at the lower end of that range.
The alternator in a car is calibrated to produce a constant voltage output of 14.4 volts for the battery charging circuit: When the engine is running and the alternator is operating, the entire electrical system in the car gets that same 14.4 volts too, which is why the headlights are noticeably brighter when the engine is running than when operating from the battery only.

When determining how many turns to wind on the transformer secondary to make a battery charger, you should have the bridge rectifier handy so you can temporarily connect it and measure the DC voltage output from it, rather than measuring the AC voltage output directly from the secondary winding. For two reasons: The diodes in the bridge rectifier have a small but significant resistance, which will cause a voltage drop of about 0.7 volts, so the DC output voltage will always be slightly lower. However, even if the bridge rectifier had no resistance at all, the DC output voltage would still not be the same as the AC voltage coming from the secondary winding of the transformer, just as a consequence of how AC voltage is measured. For example, if you take the 240 volts AC directly from the mains and wire it up to a bridge rectifier (which is what happens in any switched-mode power supply), you do not get 240 volts DC, you actually get more like 340 volts DC.

On the subject of doing the "fractal wood burning", I would not ever use the high voltage output of a microwave transformer for this, even though I do know what I am doing: You're certainly right that it is extremely dangerous, but it is also completely un-necessarily dangerous. For example, if you have a 1 kilowatt microwave (that's 1 kW of microwave radiation output), the electricity consumption will be more like 1.25 kW, since the efficiency of the magnetron is about 80%. Some power is used for the cooling fan, light bulb, turntable motor and control electronics, but that is not much - probably less than 50 watts. Anyway, the transformer in that microwave is using most of the power - say for sake of argument it is using 1.2 kW, and the secondary is producing 2000 volts: This will be at 0.6 amps, which is 20 times more than the minimum current required to have potentially fatal results if you got a shock from it. If the transformer was making 2500 volts, the current would be a bit lower, at 0.48 amps, but this is not significantly less dangerous.

Why is this un-necessarily dangerous? Because you don't need anywhere near that much current to do fractal wood burning, or to make a jacobs ladder. Either of these will work just fine with as little as 50 milli-amps. So you could do it with an old linear neon sign power supply transformer, or with an old CRT monitor/TV flyback transformer, driven at 20 kHz by an electronic oscillator circuit. These are fairly easy to build, if you can get some mosfets with high current handling capability and a switching rate consistent with the 20 kHz frequency.

[jbudik]

That last bit about the little transformers 'exciting' each other.. is that where free energy comes from? 🤣

I've built a microwave transformer arc welder about 20 years ago. It does work but very badly without having the cold start function most real arc welders have. Highly don't recommend unless it's apocalypse rules.

[douglascalhoun]

I was hoping for a Tesla coil mention but the Jacobs Ladder is really neat too.

[kelvinsparks]

Remember when you were a young boy and your dad said "don't do it " when you went to put a 9 volt battery on your tongue. I do 😂😂😂😂😂😂

[industrialmonk]

I have always made my Jacob's ladders from old CRT TVs and monitors. Im not sure if thay are any safer than the microwave transformer but the microwave transformer does look fun.

[fpt]

Thank you very much, dear sir. I'm interested in following your valuable and rich content, especially regarding renewable energy and energy storage methods, GO ON

[VibeGuy]

10vac should rectify out to something around 14vdc for the 12v battery charger. With lots of ripples without a smoothing capacitor.

[PBCSandMarci]

Very inspirational, I have no spare microwave or knowledge of how electricity works but I feel inspired either eay

[samoasisifi]

😅 simple and straightforward. If you're still here to talk about it or have kept your MT. Congratulations!

[velcroman]

First rule when working with electricity. “One flash and you ash”.

[markluxton]

To charge a car battery(13.5 volts) the charger needs to be able to go a bit higher. There are also some losses. I made one of these transformers as you described but higher than 12 volt ac. I think I had it at about 14 V ac no load. I also added a coil for charging 6 volt batteries....just in case lol

Be sure to use thick coated transformer wire so your charger can handle even big batteries in bad condition or with little charge. Recycled microwave transformer will have lots of space for thick wire with fewer turns. Mine should handle about 40 amp but I will fuse it for 30 amp charging max.


I haven't finished this charger, as I haven't sourced and purchased the parts yet. I want to be able to control the charging manually, for different charging applications/situations/conditions, and be able to monitor both the voltage and current. I don't want a "smart charger", I want to be the smart charger. With good charge control you can restore batteries with a gradually increasing trickle charge, you can safely charge different types of batteries(some do not like being charged fast), you can do a quick charge and know by the gauges you are still safe(not harming the battery or charger). You can use the charger to just put in a trickle to keep a battery warm in very cold weather. Just so much one can do with variable charge control.

Most people would probably want a smart charger ;-)

[daroniussubdeviant]

we're still thinking of you during this difficult time robert. i hope you can get back to work soon. god bless. <3

[JohnBoen]

I seem to have harvested about a dozen magnetrons...

Got any ideas for those?

[Russmayra]

Best bit was the arc welding. Could be very useful in a MacGyver situation.

[joeblowjohnny]

Awesome video video boss ! Can you do a powder coating power supply on the cheap cheap cheap microwave oven parts
? Thanks

[quangobaud]

11th Thing You Can Do With All of These Projects? 🤔
Produce lots of Ozone. 🤓

[Shoogzy]

I've made 3 of these "transformer machines" to use in "fractal burning" wood projects. It's tons of fun to build and use. Just be careful, death is possible. But isnt it always?.

[townbell]

That looks like the stereo transformer I just took apart

[davidsirmons]

Trying to create an arc FURNACE, but home's electric system is from 1945. However, oven and dryer connection is 220/240volt. Any guidance on how to create a functional arc furnace with that setup would be great. (yes, I'd have to use very long cords to do this outside, not inside). I saw TKOR's videos on this, but that advanced setup he does with 2 separate 120volt leads joining into one is not something my minimal/ancient panel is capable of. Useful info is appreciated.