>
>  > I'm looking for sugestions for this bit of analog design. I need to run
> an
> > optocoupler, but the end user could connect it to about anything. It
> could
> > vary between 12 and 240 volts both AC or DC of unknown polarity. I only
> need
> > an off/on indication and if I get pulses from the zero crossings, I don't
> > mind.
> >
> > The best I have at the moment is in the attached schematic, but every
> time I
> > look at it I think it's over complicated. Any sugestions?
>
> Maybe put a full wave bridge (eg. HD0-06) and halve the rest of it, but
> I don't see how this is going to work with 240VAC (340V peak) and 100V
> Darlingtons. I think you'll want more series resistance and some means of
> dealing with transients on top of the peak voltage (eg. TVS).
>
> Best regards,
> Spehro Pefhany
>
>

You're absolutly right about the voltage ratings on the transistors. I just
grabbed a schematic symbol and planned on picking an approprate part later,
There's pleanty of 600V rated transistors available.

The opto I was using is rated to 80mA and saturation is about 8. I originaly
picked it because It has such a wide spread when the design was for 120-240
AC/DC. A more sensitive one is probably a better choice with an active
current limiting circuit. And I like the idea of using a bridge to get rid
of one of the limiters (and both of the bypass diodes).

Food for thought, thanks,
-Denny
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