[Moved] optocoupler to be used with 230 volts ac supply

i want to make an isolated supply using optocoupler using 230 volts ac... and if there is any change in supply voltage for eg.. if the supply changes to 250 volts or 210 volts, so will the change be seen in the output of optocoupler?? i want to interface this optocoupler output to microcontroller...
plz suggest some circuit??

More details required. We have no idea what you are talking about.

well i'm making a project on embedded system where i want to display the phase voltage on adc of atmega16..To do this i want the isolation of 230 volts through some kind of optocoupler instead of transformer.. so first of all my question is-
1) is there any optocoupler available that can be directly connected to 230 volts ac supply?
2) secondly- if there is sudden change supply voltage for eg. ac mains supply changes to 250 or 210 volts, will the change in input be seen in output of optocoupler?

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Dora.

So your actual issue is that you want to monitor 230 VAC, correct? Ok, that's SOME information. Do you want to just detect the presence of the 230VAC, or actually get a voltage proportional to it? It sounds like a transformer would be the safest and simplest way to do this. There ARE linear optocouplers available-you'd just have to drop your input voltage to a usable level.

For example:

you can consider using a voltage divider and Iso-opamps like ACPL-C87, ACPL-C79. TI ISO series like ISO124...

Good Luck

kappa_am said:

you can consider using a voltage divider and Iso-opamps like ACPL-C87, ACPL-C79. TI ISO series like ISO124...

Good Luck

Click to expand...

Yeah, that looks like the best solution.

barry said:

So your actual issue is that you want to monitor 230 VAC, correct? Ok, that's SOME information. Do you want to just detect the presence of the 230VAC, or actually get a voltage proportional to it? It sounds like a transformer would be the safest and simplest way to do this. There ARE linear optocouplers available-you'd just have to drop your input voltage to a usable level.

For example:

Click to expand...

Thanks for the useful information.
I want to get a voltage proportional to the supply voltage.I just needed to know is it necessary to step down the voltage with a transformer and then use it further with the optocoupler or is there any method to detect the variation in the supply without the step down transformer. Because I doubt that transformer is a reliable source.

for eg. if I use a 12 volt step down transformer so will it provide me with exact 12 volts all the time or will it change its value to 12.1 volts or 11.9 volts?

Because of this very reason I am trying to find out some other useful method other than the transformer one , as this very small variation in the output of the transformer will affect my microcontroller adc input.