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Convert 12V DC to 220V AC

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micpic

New Member
Hi everybody! ;)

for my friends in africa, I'd like to build circuit can converts 12V (car battery) continue to 220V alternatif (50 Hz).:confused: Someone can help me, giving some idea of schematic? The installation must produce minimal 5A.

thanks :)
 

Torben

Well-Known Member
micpic said:
Hi everybody! ;)

for my friends in africa, I'd like to build circuit can converts 12V (car battery) continue to 220V alternatif (50 Hz).:confused: Someone can help me, giving some idea of schematic? The installation must produce minimal 5A.

thanks :)
One 12V car battery? I'm guessing it's probably not a high-priced RV battery, is it? I don't know how much run time you'll get at 5A current draw on it, but I bet you'll be disappointed.

I hate to discourage anyone, but if this were my call, I'd buy one. Building an inverter like that will probably cost more than buying one. And it's a relatively dangerous project, as such things go.

Disclaimer: I'm a hobbyist, not an electrical engineer, so maybe somebody here has a more hopeful answer for you. I haven't seen much on the net to make me think this would be a good beginner's project, though. :)


Good luck, whatever you decide!

Torben
 

micpic

New Member
Thanks for your reply torben! :eek:

But, I think it's possible to realize that, i already found someone using it for other application (less current). About design, 5A why? because, my friend uses lamps (every lamp has 75w), TV,radio and one refrigerator: domestic application :eek:, and others electromenager.

someone has idea? :)
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Simple answer, BUY ONE - they are really exceptionally cheap these days, far cheaper than trying to make one.

However, your requirement for 1200W or so really calls for more than a 12V battery, and massive batteries at that, if you expect more than a few nmutes battery life?.
 

micpic

New Member
Thanks for your reply guy, :p

I'm agree so, I want to know what circuit use to build this project, I already found in google, a lot of schema use boost convertissor, others use H bridge, but to calculate power and consumation :confused:

thanks
 

Nigel Goodwin

Super Moderator
Most Helpful Member
micpic said:
Thanks for your reply guy, :p

I'm agree so, I want to know what circuit use to build this project, I already found in google, a lot of schema use boost convertissor, others use H bridge, but to calculate power and consumation :confused:
I don't think there's any decent useable designs on the net anywhere?, at least I've never seen any, or seen any links to them posted here - and there are always many such requests on the forums.

Power and consumption is dead easy to calculate - you want 5A at 220V, that's 5 x 220 = 1100W. Assuming 80% efficiency, that's 1375W drawn from the battery. So at 12V it will consume roughly 115 Amps, a 24V version would draw 57.5 Amps.

Assuming your 12V battery is off a car, and possibly 50AH? - which gives an estimated 2 minutes battery life! - a 100AH battery would give you 4 minutes!.
 

audioguru

Well-Known Member
Most Helpful Member
You should look at the entire project on the Japanese guy's website to see how weak his inverters are.

The first one is shown to drop its ouput voltage when the load is only 10W and has a max battery current of 3A which is 36W.

The second one has an output voltage of 110V without a load, 100V with a 40W load and 90V with a 140W load.
http://hobby_elec.piclist.com/e_ckt30.htm

Many electronic devices don't work from a square-wave. Some radios and TVs, some computers and most electric motor speed controls don't work.
Light dimmers might blow up.
 

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Hero999

Banned
Use compact fluroscent lamps, they use 1/5th of the power so you can design your inverter to output just 1A and save yourself a lot of bother.

Even better, just buy 12V compact fluroscent lamps, the you don't even need to bother with the inverter.
 

micpic

New Member
thanks for your reply :)

Many electronic devices don't work from a square-wave. Some radios and TVs, some computers and most electric motor speed controls don't work.
Light dimmers might blow up.
I think to use harmonic filter composed by self and capacity, this filter eliminated harmonic composant and keep fundamental.

thanks ! ;)
 

audioguru

Well-Known Member
Most Helpful Member
The output impedance of a powerful inverter is too low for an LC filter to work.

Even if the harmonics of a square-wave are removed, the fundamental frequency's voltage is 0.707 times too low. The harmonics are half of the power from the inverter.
 

micpic

New Member
ok thanks! now i understand, :) so could you give me an idea to do if i want to have mini 5A in output at 220V?;)

to have 24V in input (Two battery) or others methods?

thanks! :eek:
 

audioguru

Well-Known Member
Most Helpful Member
5A at 220V is 1100W and the inverter will heat with about 220W so the 24V battery will have a current of 55A. Two big car batteries will power it for a little over 1 hour.

A square-wave inverter is simple but many loads won't operate properly.
A modified sine-wave is complicated.
A true sine-wave is a very complicated circuit.
 

micpic

New Member
ok everybody! :)

I think that someone here doesn't built the same project, so I will believe to realize this, why others person arrive to realize the same product, why me? You tell about complication, I think it's not if you'll really decide to realize this!

for me, the first problem is to find what battery could produce powers that i need, and the second is to find the good transfo, and to calculate values of LC for my filter.

thanks for your help guy! ;)
 

audioguru

Well-Known Member
Most Helpful Member
Why make a low frequency square-wave inverter then waste most of its power by heating a huge filter?

Instead, make a switched-mode PWM inverter that uses a small ferrite transformer at a high frequency to make a 320VAC square-wave which is rectified and powers the PWM Mosfets that chop it into a 50Hz 220VAC sine-wave. Then the filter parts are tiny and efficient.
 

mneary

New Member
for me, the first problem is to find what battery could produce powers that i need, and the second is to find the good transfo, and to calculate values of LC for my filter.
1100W, over > 20 minutes, is best supplied by a generator.
 
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