configuring AD converter in a 12F615

[Darrel Taylor]

Darrel, can you please explain how you arrived at the value 117 for the Vref_AD constant? I would have expected it to be 0.6/5*1023 = 122

The internal fixed references are not very accurate, so you have to read the actual value to determine the number to use.

For my project I was able to use another ADC pin to monitor the supply voltage so all is good (for the time being).

Thats a bit like lifting yourself up by your own bootstraps.

[Aussie Barry]

Thanks Darrel.
I am using the other ADC pin to sense the pre-regulator voltage (via an appropriate voltage divider).
If the pre-reg voltage drops below 5.3V then the circuit will flash a "Low Battery" indicator and disable any future water pump operation.
I am trying to save the 6V SLA battery from a harmful depletion condition.

Cheers
Barry