Quick AVR question

[TrickyNekro]

Hello again...

If I connect a pin (I/O) of my ATMEGA8 at 13V via a 1MOhm
resistor will things go puff or I'm ok???


Thanks in Advance,
Lefteris, Greece

[dunk]

i don't know to be honest. you would need to check the datasheet for the AVR I/O pins maximum current sink and resistance and calculate the minimum value of resistor needed.

the correct way to do this is to use a voltage divider. far less complicated to work out but one more resister in the circuit.


dunk.

[TrickyNekro]

It's in a place I really can't use a divider...
I want to witch a MOSFET... and if I place a resistor to ground it turns on... and that's not good...
I'm trying out the op amp buffer right now....
I'm hell confused over this circuit...
I'm trying to make a kill switch with a mosfet gate...
One switch power up the circuit until microcontroller starts and opens the mosfet gate....
Maybe I'm having a wrong approach...
Maybe..... Darn I think I figured out the way!!!
I know it's silly... But sometimes you just don't act right!!!

Thanks for the answer!!! And thanks for the inspiration that post gave me!!! really!!!

Best Regards, Lefteris
Greece

[dunk]

I want to witch a MOSFET...

ah. 2 suggestions:
1. get a MOSFET driver. there are special drivers for driving MOSFETs from TTL logic levels.
2. get a TTL triggered MOSFET. maybe this one: http://www.fairchildsemi.com/ds/RF/RFP30N06LE.pdf


dunk.

[TrickyNekro]

I had problems cause I wanted exasperated grounds and that...
Really messy things....

Thanks a lot for the advice! It seems that the IRF540 fully responds to the TTL levels with no problems.
The gate input for high is somewhere near 4V - 5V to 20V if I'm right...
So 5V is of TTL level...

I can do the trick with a op amp if I have a so serious problem...

Thanks for the interest and replies!
Best Regards,
Lefteris, Greece

[Admin]

If I connect a pin (I/O) of my ATMEGA8 at 13V via a 1MOhm

I don't quite understand your question, but the typical AVR will fry above 5.5V.

[pomprocker]

maybe sharing a schematic would help