piclist-bounces@mit.edu wrote:
> So I'm going
> to sense voltage on the DC input, and it has to be before the diode. 
> I could add another diode to prevent the PIC from ever seeing a
> negative voltage if the user uses a wrong-polarity wall-wart.  But
> I'd rather not if it isn't strictly needed.  

If by sensing you mean just presence/absence (as indicated in the
original mailbelow ), then why not an ac-sensing optocoupler, for
example ltv-814 plus two resistors.

>>> I have a design whereby I want to sense the presence or absence of a
>>> voltage that is well above +5V; maybe up to 15V, say.  This voltage
>>> could be negative as well, at least until the user figures out they
>>> have  their DC input backwards...
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