Arduino BT reverse polarity "protection"

So on the Arduino BT page I read the following:

Don't power the board with more than 5.5 volts to the or reverse the polarity (power and ground pins) of your power supply, or you might kill the ATmega168 on the Arduino BT. The Arduino BT can, however, run with a minimum of 1.2 volts, making it easier to power with batteries.

I'm looking at the reverse polarity part:

In the schematic of the BT board, I notice that there is a diode connected in parallel to the battery input. It looks like that if a battery is put in backwards it will simply fry the diode, and then proceed to short any battery that is placed in it afterwards. does this sound correct?

I'm basically trying to figure out what the best way is to run this thing off a single AA and still have some sort of peace of mind against putting a battery in backwards.

Thanks! :)

Usually that form of reverse polarity protection relies on having a fuse upstream of the diode that will blow open if the battery is hooked up with the wrong polarity.

Lefty

thanks for the reply!

yes that makes perfect sense. but in the schematic its just the diode across the battery terminals. so is this a one-shot protection scheme? :wink:

or am i missing something here?

It's not a very good reverse-polarity protection scheme, because it really needs a fuse in line with the battery. Maybe you could add a fuse? Make sure the fuse is rated so that it blows before the diode does!

So if I understand it correctly, the external power supply of the ArduinoBT cannot be more than 5 volts? Thus, when designing a battery solution for the Arduino power jack, it must be at maximal 5,5 volts? How many amp should it be?

Another question: Can you put a the GPRS shield from Libelium on the Arduino BT, without having power issues? (http://www.libelium.com/squidbee/index.php?title=New_GPRS_module_for_Arduino_%28Hilo_-_Sagem%29)

Kind Regards

-Royale