Limiting the voltage....

Hi,

I think I have aked this before but never really got a good answer, I have a 6v-36v line and I want to place a LED (and a Atmega128) in this line and use it to detect the ignition status of a car.

Wouldplacing a BZX84-C3V0 between this line and GND do it? if not what is best way?

Thx in advance

if this car has a alternater why dont you check if current is comming from it
sorry i dont know what a 'BZX84-C3V0' or a 'Atmega128' is.

Clarify what I'm trying to do

I want to determine when a car / truck ignition is turned on, the voltage can be between 6v - 36v, I want to monitor it with a Atmega128 MCU, I also want a LED to indicate the ignition is on.

How can I safley attatch a small SMT LED and a I/O pin of a Atmega128 to a line that can have 6v-36v range.

Thanks

Anyone?

Hi,

I really could do with adive on this, anyone got any clues?

Just want to limit the voltage from a input of 6v-36v to a LED / I/O pin of a MUC, so 2.5v should be fine.

Thx

Re: Anyone?

Scarr said:

Hi,

I really could do with adive on this, anyone got any clues?

Just want to limit the voltage from a input of 6v-36v to a LED / I/O pin of a MUC, so 2.5v should be fine.

Thx

Click to expand...

On a PIC all you need is a series current limiting resistor, but according to recent posts the Atmel processors don't have protection diodes, so you would need to add external ones.

As it's in a noisy environment, it would be a good idea to use two series resistors instead of one, and fit a zener diode from their junction to ground, a 12V one would be fine. This will help to keep large spikes from the processor!.