If I am to use a 12volt car battery to power this circuit Circuit drawing of DC/AC inverter (2) if I connect the positive terminal to the source pins of the two p channel mosfets and also to the controller i.e. IC1 etc.
The source pins of the n channel mosfets are connected to ground and as are the components of the controller in this link Pattern drawing of DC/AC inverter (2) control unit
This leaves me with a problem I don't have an answer for and that is where do I connect the negative terminal of the car battery to in the circuit?

 

Where it says "GND" on the pcb layout.
Is this what you were asking?

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Ive been told that this is only for grounding and has nothing to do with the negative terminal or as I would call it the nuetral terminal.

 

Then GND the chassis, what are you grounding it to? a stake in the ground, a cold water pipe?

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hi James,
Look at this drawing.

The BLUE is the 0V wiring on the pcb and to the 12V battery..OK?

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I think that was my first thought eric if you mean what I think you mean. I have three nuetral wires, one coming from the ground of the controller and the other two from the source of the mosfet pins you indicated so I'm guessing my first guess was correct.
However I have no connection with my wiring between the ground of the controller and that of the two mosfets, they all connect to the nuetral or negative terminal of the battery independently, I'm assuming it makes no difference as long as they are all connected to the negative terminal it doesnt matter if they are in series or in parallel when the connection is made or would I have to ensure all the grounding is centralised into one wire and then connect that wire to the negative terminal do you know what I mean.

 

Unless you want an isolated supply for any reason, bonding bother the 0V DC supply and the neutral to earth is generally the done thing as it makes it impossible for the DC to float at mains potential.

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so hero what you are saying is have a configuration that will enable me to ensure that the nuetral part of the circuit is at earth potential at all times by connecting it to a pipe, stake in the ground or chassis like Bill suggests as well as the nuetral of the battery. It sounds like the sensible mans choice to me.
I figure this is best done by wiring all the nuetral wires to the same bit of track where I can have a single wire which will connect to the negative terminal of the battery and also have another wire which will connect to ground, how does that sound? i.e. have all the blue lines in erics diagram connected to a single track where I can have two wires leaving it, one to earth and one to the negative terminal. by the way eric thanks for that diagram it is well appreciated and so has all your other help been.
My only doubt about this idea of mine is will the track I'm talking about connecting all the nuetral wires to be able to withstand the current I'm assuming will flow in it, or is it not worth worrying about?

 

I'd like to point out that car chassis is connected to the 'negative' terminal already.

If you're worried about the current handling of the track, just beef it up with solder... no harm done =]

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Hi James,
If the invertor is driving a lamp, you dont need any grounding to EARTH.

If you connect the 0v [neutral as you call it] to ground/EARTH, its possible that you could get a electric shock from the [line] side of the output, if accidentally touched it, while standing on the ground...

I would suggest you leave it earth free for the lamp circuit.

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hi,
I agree.
Also James, your car chassis isn't connected to EARTH, unless you have metal wheels.

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Or one of those poxy earthing straps...

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What is a joule per second?

 

[cheers eric "If you connect the 0v [neutral as you call it] to ground/EARTH, its possible that you could get a electric shock from the [line] side of the output, if accidentally touched it, while standing on the ground... had a feeling it may have been a dodgy idea is it ok to have all the nuetral wires connected to the negative terminal independently or should I connect them to a single bit of track where I would then use a single bit of wire for connecting them to the negative terminal?

Good tip erossenin about beefing up the solder.

 

hi,
I would link ALL the 0V's together on the PCB, use heavy gauge wire, then from the link connect a heavy wire to the battery negative.

Also on the +V side, do the same link ALL the +V's together on the pcb, then from the link connect a heavy wire to the fuse.
From the other side of the fuse, another heavy wire to the positive terminal of the battery.

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PIC tutorials:
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Bill's: www.blueroomelectronics.com/