I meant a microwave transformer 12 V DC to 220 V AC...
I'm trying to make an inverter out of the old stuff that I can lay my hands on. So I need this 12V DC to 220V AC transformer. Cud I use the microwave transformer or a TV one by rewinding the secondary so as to be able to provide only 220V?? How many turns will I need?

Is it possible to just simple reverse the step-down transformer n get a step up transformer? By changing the primary to secondary n vice versa? Any other type of transformers I can use, please suggest.

 

It's probably possible to rewind the microwave transformer, but using a step-down transformer backwards will be lots faster.

 

You need a good circuit to drive the transformer.
The low voltage winding of the transformer must use a thick enough wire to carry enough current for the power output you need. It is difficult or impossible to wind very thick wire on a transformer that is assembled so you might parallel many thinner more flexible wires.
Every transformer is different and needs a different number of turns. Guess how many?

Inverters are simple square-wave that does not drive electronic products, or modified sine-wave that is more complicated but most products can use, or pure sine-wave with a very complicated circuit. Which one?

 

To beenthere:
Would any transformer do the job, for instance, the mobile charger which used to have the step-down transformers, can they do the job? And it does the job without any changes to the transformer, just the inverting would do?

To Audioguru:
I understand. Well, I may need to then parallel atleast 4-5 layers of thin wire? Regarding the wave type, I would first make a rectangular wave (or a square wave) and get the RMS value to 220V AC. I wud like to keep them as simple as possible in the begining. Many components don't work, but tubelights will work right?? Just one is enough for the starting.

I have another doubt. Suppose I use the AC mains in the house to charge the battery of my inverter, something very similar to the UPS, so when the power goes, the battery gets into action. Now, will the refridgerator or other such circuits, which demand a current surge to start up, blow off the fuse. Any way I can use the house wiring but also not deliver the power to a fridge so as to keep it off, apart from manual monitoring.

 

Hi coolguy_ar......

Modified Sine wave Inverter is better than square wave inverter.

Modified-sine inverter can be built from scratch like I did (likewise I rewinded old microwave xformer).

Use #3 AWG wire (5.6mm in diameter) w/ 105A max current for PRIMARY winding w/c is more thinner if you use parallel thin wires like "4" strands of #10 AWG wire (10.4mm in diameter).

I hope it helps you out...

Here is my diagram: It has an UNDERVOLTAGE CUT-OFF CKT. that can automatically stops the inverter if the battery is LOW (approx. 10V).

hello kabayan!



have you done this circuit already?? post pics??

cheers!
Ralph

 

Hi Ralph......Magandang araw sa iyo!

Yes I did. But I don't have a pics. of it.

I built it using old electronics parts, excluding the CMOS IC (w/c is very tricky to find in the market).

I'm just using it when there is a power outage.

 

I Juan,
I wish you will fix the connections of D3 and D4 on your schematic.

 

I meant a microwave transformer 12 V DC to 220 V AC...
I'm trying to make an inverter out of the old stuff that I can lay my hands on. So I need this 12V DC to 220V AC transformer. Cud I use the microwave transformer or a TV one by rewinding the secondary so as to be able to provide only 220V?? How many turns will I need?

Is it possible to just simple reverse the step-down transformer n get a step up transformer? By changing the primary to secondary n vice versa? Any other type of transformers I can use, please suggest.

I have just built a valve amp and couldnt find a cheap transformer above 55VAC so just used a mains to 18VAC transformer backwards to get the 180VAC I needed. Clearly you need to be careful how much current you put in and take out of the transformer.

 

Thanks Audioguru..

HERE IS THE EDITED DIAGRAM:

 

I have just built a valve amp and couldnt find a cheap transformer above 55VAC so just used a mains to 18VAC transformer backwards to get the 180VAC I needed. Clearly you need to be careful how much current you put in and take out of the transformer.

Yeah thanks a lot. I'll be tryin out that asap. There's one more thing I had asked for. Can I prevent the break of the fuse due to the Fridge surge??Plus I intend to make the inverter like a UPS, with the AC current charging the battery when power is there, and when gone, the DC powers a set of tubelights n fans, already part of the house circuitry. If u require any more information, please do ask.

 

The microwave transformers used in the US output about 2200 volts with 110-120 input. That would be close to what you are wanting (12 in, 220 out) without any mods. Current would be limited by the size of the secondary wire. I realize it has been a while since anyone posted in this thread.

 

I meant a microwave transformer 12 V DC to 220 V AC...
Cud I use the microwave transformer or a TV one by rewinding the secondary so as to be able to provide only 220V??

I just finished mine today, was scratching around,found 12v to 220 inverter with the transformer crisped. I pulled out a microwave transformer I had lying around, no rewiring, just grabbed a centre tap right out of the secondary and soldered a tap to my inverter. My transformer(microwave) is welded so no possibillity of rewinding, but the secondary is so neatly machine wound that I counted the rows and layers and took a small, sharp screwdriver and liberated my centre tap.

I also sliced the turn next door, but the repair was easy, 'cause a bit of slack becomes available when you pull it loose from the stack,if you like I"ll send pics.

My radio and bench light has been running all afternoon and nothing is even a little hot.

Wow, not bad for a mechanic?
So you can tell Mr Bean over there, its really much easier this way after all.

 

I thought i'd add an often overlooked source:

"Dead" UPS/uninterruptable power supplies for computer equipment. They are Very Often simply discarded when the battery is no longer good (at least in the US). Often the price is "Free", since they can't be thrown in the trash. The circuitry inside provides most everything needed, and if you can get a 2000VA+ UPS for free, you have all the transformer you need. In addition to lots of other useful bits, such as a case.