>What I have done in the past, when I have a circuit whose normal range of
>output is less than 5 volts, but could go above under unusual situations
>is to use a 5V rail-to-rail opamp set up as a buffer between the circuit
>and the A/D converter. What happens to the opamp when its input voltage
>goes above 5V is another story - if there is an input resistor of a few K,
>it should be OK.


You can also put in your own "protection diode" - a series resistor of
(say) 1K, a diode to +5V, then another 1K series resistor to the PIC A/D
input pin. - this last one to ensure that your diodes are doing the
protection, not the PICs. I've done this also, and it seems to work well.


Larry Bradley
Orleans (Ottawa), Ontario, CANADA

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