Are Pic pins normally LOW when the PIC is un-powered??

[amgen]

With pic powered down, I don't think you can supply voltage/current to most all pins. The limit diodes direct the current back to Vdd powering up the device and probably not run the program properly.... per Archangle.
don

[falingtrea]

Most pins on a PIC can drive hi efficiency LEDs directly. Either connect the LED to 5V instead of 12V, or flip the LED and connect it to ground. Size the resistor for 3-5 mA of current at 5V.

[AvionicsMaster1]

I'm away from my computer with a schematic drawing program so I hope this conveys my idea adequately. With no power to the PIC the LED would be powered on by the 12VDC thru resistor to ground. When PIC is powered a HIGH of more than 3ish VDC at the PIC pin would be enough to turn the LED off. The diode to the PIC would protect the PIC from sinking or sourcing current from the 12VDC source.

12VDC
|
Resistor
|
K--Diode-A---PIC pin
|
LED
|
Ground

I hope I'm using some semi-solid logic in this idea but if this isn't a good idea please let me know.

[amgen]

with what you describe, the LED won't turn off.... 3vdc'ish on led from pic will just light the LED. There are small (6 or 8 pin) normally-closed (form B) solid state relays, then the PIC energizes the SSR to turn off the led.


don

[AvionicsMaster1]

OOps! Sounded good when I wrote it. I hope I get it right next time. Sorry about that.