Chip Selection

[isaac]

Have you checked with a scope on the dc side if its fluctuating or stable?

[AMay]

No, but I have assumed it is pretty good, as its source is the trickle current to the burglar alarm back up battery. I put my Fluke meter on it, and as I recall the ac ripple south of the vr was OK.

[mackrackit]

What is the source of the inputs? Maybe there is a spike now and then.

[AMay]

The power comes from the trickle charge to a 12 v alarm battery. I have a pretty well filtered supply because of the supply wires running parallel to 120v AC wires.

[mister_e]

I've never, and will never trust any Pull-up thing. As per their definition they are weak. nuff said. In a shielded enclosure with no external inputs, running off battery maybe they're fine... but not something I would use again on a final product since I already got issue with some handheld car instruments I've made years ago. Ununsed i/o are set to input and tied to GND directly, or with low value pull-down.

Some will say set them as output and left them floating... ok .. could be fine as long as you always have supply on your board.

GOOD ground plane will also help.

[mackrackit]

The power comes from the trickle charge to a 12 v alarm battery. I have a pretty well filtered supply because of the supply wires running parallel to 120v AC wires.

The input pins will not handle 12 volts. It is a wonder it works at all.
Or.
You misunderstood the question....

[Charlie]

The input pins will not handle 12 volts. It is a wonder it works at all.
Or.
You misunderstood the question....

Or maybe you missed the original post where he states:

"I have a 100uf cap at the input, and a 78L05 regulator, a .1 cap on the 5v side."

[Demon]

Moved from FAQ.


PIC selection guide:
http://www.microchip.com/stellent/id...GE&nodeId=2551

How robust is a PIC?
http://www.picbasic.co.uk/forum/showthread.php?t=15993

Robert