Hi everyone. I'm about to build an Arduino (tweaking the eagle files now). But my big issue is this--it seems like using a 9V to run a board with a 5V requirement is overkill. Basically, I don't want to use a crappy 9V 150 mAh battery. So here are my questions:
On the LM7805 (voltage regulator) datasheet, it says that the dropout voltage (input-output differential) is just under 2 volts for a 5 volt output at 500mA current. So why do you need a 9V battery? Seems like you'd be fine with 7V, even up to 1A current draw (according to the data sheet).
Has anyone tried replacing the LM7805 with a low-dropout regulator, e.g., the LM2940, with a dropout voltage at under .3 volts at 500 mA? Seems like you could use this instead and put in a nice 6 volt 5-AA NiMH 2500 mAh battery pack, which is so much nicer than a 9V. Especially if you like to drive servos.
It says 9v because the most common power supplies you find are usually 9v or variable... also
for beginners they associate that with the 9v battery and its guaranteed to last for a bit..
usually i run it at 7.5v
the next arduino board called arduino "Diecimila" (to celebrate the 10000 boards sold) will have a low dropout regulator
just out of curiosity ar eu making your own board for cost reasons or because you want to add some thing to it?
It says 9v because the most common power supplies you find are usually 9v or variable... also
for beginners they associate that with the 9v battery and its guaranteed to last for a bit..
usually i run it at 7.5v
the next arduino board called arduino "Diecimila" (to celebrate the 10000 boards sold) will have a low dropout regulator
Ah, that makes more sense. Thanks for the response.
just out of curiosity ar eu making your own board for cost reasons or because you want to add some thing to it?
massimo
I'm making my own board to add a small breadboard prototype area. So I'm tweaking the prototype board, the one with the components shoved to one side & a bunch of perf board vias. Basically, I'm deleting all the vias and extending the board space to fit a 1.86" x 1.36" breadboard. It'll be a little more compact than using a bb shield, and since I'll also make my own programmer, I don't need USB. Also, I put screw holes on all four corners. Before I'm through, I'm sure I'll tweak something else too.