Electronics > Proteus

How to separate two GND in Proteus

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Chriss:
Hi!
I run into an issue with Proteus 8 on my simulation when I try to use the scope.

I designing a circuit where I have a AC main high voltage side separated from a low voltage site.
These two circuit's are separated with an optocoupler.

When I use my scope I have some wrong measurement's.

My major question is:

When I have a simple circuit with an AC source, do I have to connect it to a GND?
When I disconnect GND from the high voltage side, Proteus can't simulate, running into error.

Actually, how can I tell the scope not to use the DC/low voltage side GND as a reference when I scoping the High voltage?

thanks.

PlainName:
It needs to be referenced against something, which is typically gnd. Unlike real life, you won't blow the scope up if you shove 240V up the ground pin :)

Chriss:
Yea, you are right, but if I put a optocoupler MOC3021 and the low side is a DC circuit, the high side ( where the diac is ) is an AC circuit.
If I didn't put a gnd to the high side and try to simulate, I get always an error like some timestep error.

If I put a gnd to the low and high side, I have a bad scoping signal.
I assume the two gnd's are act as the same ref.point.
Like they are in real the same gnd line.

In real life these two gnds have to be separated.
How can I achieve this in Proteus 8?

Thanks.

PlainName:
I am not sure how you are doing this: are you treating AC1 and AC2 as the signal and ground to the scope? Or are you having AC zero crossing at scope ground and the signal either AC1 or AC2? It sounds to me like the former, and that won't work because the AC signal isn't referenced to anything.

The latter, where AC1 and AC2 both swing positive and negative (alternately, of course) relative to ground, is what you want, I think. So far as I know, you can't have a floating signal because, well, it's floating and not referenced to anything. If you don't want the AC to swing below reference ground you can add a DC offset to it which shouldn't affect how your circuit operates if the two sides are really separate.

Can you post your circuit? A printout would be best since not everyone has your version of Proteus (or even any version).

Chriss:
So, here is a really basic schematic where I also have problem to simulate with Proteus 8.

I posted the "project" if we can call this so.  :-DD
It is just to show one of the problem I have when I try to use AC and DC side in the same schematic in Proteus 8.

When I try to simulate the circuit without the GND connected on the AC side, then if I open the switch I get an error
like on the screen. I dont really understand what is that error meaning.

If I connect the GND on the AC side, then everything is working, no error, but on a more complexe schematic I got a signal distorsion too.

So, I'm not sure what is wrong and how to really separate the AC and DC ground's.
Or how to take measurement with the scope but to be suere the scope is referencing to the AC GND if I measure the AC side etc.

Thanks for any advice.

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