AC waveform centered to 2.5V ?

[UroBoros]

I need to trace the AC line voltage with ADC in a dspic.

I want to use it without transformer - that is with optocoupler.

I need to transfer AC to otherside (DC side) centered at +2.5 volts (0-5V) -so AC opto is needed with linearity.

I located data sheets for IL256,HCPL354 (AC optos). None of them says 'liner'.

But I have located data sheets like HCNR200 which says 'linear', but not AC.

How can I tackle this situation?
What about two linear DC optos like a voltage divider in the DC side?

Thanks

 

[IanP]

How about the IL-300 ..
Have a look at these examples:
**broken link removed**
**broken link removed**

You'll have to scale the voltges at both sides ..
For example, scale the voltage down to +/-1V with, say, 3Vdc offset at the AC side, and then whatever you need to suit the ADC at the dc side ..

IanP
:wink:

 

[UroBoros]

You'll have to scale the voltges at both sides ..
For example, scale the voltage down to +/-1V with, say, 3Vdc offset at the AC side, and then whatever you need to suit the ADC at the dc side ..
IanP
:wink:

Thanks for the reply.
On the DC side offset, I Have some idea how to do.
But on the AC side, apart from dropping using some resistors, how to introduce offset?
Thanks

btw any opinion about the attached method?

 

[IanP]

One way is to introduce to the AC side something like an isolated, floating 5Vdc generated be a tiny (1W) dc-dc module, dc power taken from the dc side ..
Once you have that floating voltage available, you can reference it to the Neutral (0Vac) and that should allow you to create a dc offset, supply an opamp that drives optocoupler and so on ..

The “dualopto” circuit is not linear .. I guess it will better serve as a zero-crossing detector ..

:wink: