M. Adam Davis wrote:
>
> Use a resistor, cap, and zener (no a/d):
>
> 0-30vdc+-----/\/\/---+----------+-------PIC I/O
>                      |          |
>                      |          |
>              +--|>|--+   +--||--+
>              |           |
>              |           |
>              |           |
> Gnd----------+-----------+
>
> To take a reading, drop the pin to gnd for a few ms, then float the pin
> and check it to see when it goes high.  Put it on an interrupt pin or
> interrupt on change and you can just use a timer.  Put it on the CCP pin
> in capture mode and you'll get the interrupt and the exact time when the
> pin changes.
>
> If the voltage is over 5 volts then there will be some current draw, but
> only very little (much less than a regular voltage divider)


Sorry no prize! ;o)
It doesn't totally switch off. And the current
draw will be identical to the 2R voltage
divider, as at 30v the top resistor will
still drop 30v-5v and I =E/R
I do agree that at lower voltages approaching
5v it will draw a bit less current though.
-Roman

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