DC-AC converter

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Mike
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DC-AC converter

Post by Mike » Fri Apr 23, 2004 4:49 am

i need to know what kind of chip can convert a 12V DC input to a 12V AC output to drive a 120-12V transformer backwards. Basically, what I want to do is make a device that if the power goes out I can power a lamp, small radio or even possibly a small 13" TV??<p>i will connect a standard car battery to the input and need 120VAC output.

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Re: DC-AC converter

Post by ajc-28 » Fri Apr 23, 2004 6:16 am

You don't need a chip. All you need is two npn or PNP transistors hooked up to the primary of a transformer in a multivibrator configuration so that the circuit oscillates at about 60 Hertz as determined by the selection of the R and C values. The secondary of that transformer would then be AC. I can't draw the diagram here but I am sure you can find the circuit at dozens of locations on the internet.

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Dave Dixon
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Re: DC-AC converter

Post by Dave Dixon » Fri Apr 23, 2004 7:00 am

Try a search on "power inverter" or "dc inverter".
That is what the circuitry is called. Good luck,
Dave

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Externet
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Re: DC-AC converter

Post by Externet » Fri Apr 23, 2004 8:57 am

Hi.
Find a deceased uninterruptible power supply; 9 of 10 only need battery replacement to be alive again and will power a few lights and television.
Or get an inverter for automobiles, they are inexpensive.
Miguel
- Abolish the deciBel ! -

Mike
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Re: DC-AC converter

Post by Mike » Fri Apr 23, 2004 7:58 pm

thanks ajc-28, i will look.<p>and i dont want to buy one, i want to build one.

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Re: DC-AC converter

Post by josmith » Sat Apr 24, 2004 9:31 am

I've tried to make a "junk box" inverter. It's an interesting project but if you really need an inverter, you're better off buying one.
If you use the transformer windings as part of the oscillator, the frequency will be load dependent.
Remember that each amp out is going to draw more than ten in so you need heavy input components and a heavy transformer.
Have fun, then go buy one.

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Re: DC-AC converter

Post by Mike » Sat Apr 24, 2004 7:18 pm

heavy transformer?... hmm guess the 2A one i have wont work...<p>how do those ones you buy put out so many watts yet be so small?<p>Can somebody describe how to connect the transistors like ajc-28 said?

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Re: DC-AC converter

Post by ajc-28 » Tue Apr 27, 2004 6:50 am

I'll try to describe the circuit using NPN power transistors. Use a center tapped primary with the center tap connected to + DC supply. Connect the
collector of each transistor to the other primary connections, one transistor to one primary wire.
Connect the two emitters to the minus supply rail.
Now take an RC network (resistor and capacitor in parallel) and connect one of the transistor base wires to the opposite collector. Take another RC network and repeat for the other transistor. The values of R and C determine the frequency, which you can experiment with. Start with 10K and 47 ufd.
When you apply power the circuit should oscillate, and there will be an AC voltage at the secondary of the transformer.

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Re: DC-AC converter

Post by dyarker » Tue Apr 27, 2004 6:51 pm

The 2A transformer will work, but 2A on the 12V side is less than 200mA on the 120V side.<p>That means less than 24W; it won't power the lamp, the TV is out of the question.
Dale Y

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Re: DC-AC converter

Post by Mike » Wed Apr 28, 2004 4:48 am

well, it would power a 20W or maaybe a 25W right? i mean, wouldn't it at least light it?

Mike
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Re: DC-AC converter

Post by Mike » Wed Apr 28, 2004 4:49 am

oh, and i don't have a center tapped primary, only secondary. Will it still work?<p>the secondary is 12V and the primary is 120V, so I would want to use it backwards anyway, right?<p>[ April 28, 2004: Message edited by: Mike ]</p>


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Re: DC-AC converter

Post by dyarker » Wed Apr 28, 2004 5:15 am

Yeah, anything under 20W is okay, but you can buy a lot of 12V bulbs cheaper and easier.
Dale Y

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Re: DC-AC converter

Post by Mike » Thu Apr 29, 2004 5:08 am

if you can't open the picture by clicking on it, it will come up with a Remote Linking Forbidden error.<p>You need to right click on it and save as.

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dacflyer
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Re: DC-AC converter

Post by dacflyer » Fri Apr 30, 2004 3:00 pm

well for bout 40.00 you can buy a 400watt inverter made by husky,, i got 3 and they seem to be pretty good for the cost...
altho i am looking for a true sine wave inverter, just haven't found one yet... i want at least a 1kw if i can find one ....
the 400 watt ones are modified sine wave... they work good for most things...only things that do not work too good are theose that depend on line frequency like clocks etc.. makes them run too fast..lol

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