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Join Date: Nov 2009
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# pls explain this circuit to me

11/28/2009 11:26 AM

http://project.irone.org/dc-to-ac-inverter/

The circuit in the above link is dc to ac inverter.

the main concern i post this circuit is i want to understand how the output of the circuit can appear as a waveform(sine wave or square wave is not my concern) with a positive and negative cycle.

what is the main factor or process that made the output of the the 555 timer which is a a square wave that alter from 0-12v to come out with a waveform that has positive and negative cycle at the secondary side of the transformer?

how this happen?and why?

is the purpose of the LC circuit use to shape the squarewave to a sine wave and has nothing to do with the positive and negative cycle thing?

Please do explain it to me .Thanks a lot.

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#1

### Re: pls explain this circuit to me

11/28/2009 12:46 PM

I believe your question is not how you get a sine wave but how you get a sine wave that swings positive and negative about zero?

If that is your question, it's because transformers only transform ac voltages, not dc biases. So, the secondary output is completely independent of whatever the input was, assuming you are able to live with any dc current flowing in the primary.

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#2

### Re: pls explain this circuit to me

11/28/2009 1:26 PM

The output of this circuit will give an alternating current - but the voltage is floating - it will not be 'positive' or 'negative' until it is referenced to 'something'.

To get an output with excursions above and below earth potential, one of the transformer outputs should be earthed.

"is the purpose of the LC circuit use to shape the squarewave to a sine wave and has nothing to do with the positive and negative cycle thing?" - yes.

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#3

### Re: pls explain this circuit to me

12/01/2009 11:17 AM

Like JohnDG said, the output (Secondary) side of the T2 is isolated or not tied to any reference. If you draw a tap from the center of that secondary winding and tie it to the ground, only then you can see the ac wave form cycle from somewhere +115 to zero and then to -115, and so forth.