Use separate 5v supply for Arduino

[rbtying]

Hey all,
      How would you use an external voltage regulator for an Arduino?  I've got a 5v switching regulator, but can't figure out how to wire it into the Arduino circuit.  I have tested it on a separate ATMega328 board that takes 5v in, but I can't removed the 7805 regulator from the Arduino board.  Is there anything bad that could happen if I just wired the switching regulator in parallel?  As in, switching regulator 5v out -> Arduino 5v out pin, GND -> GND, Vin -> battery?

[Soeren]

Hi,

I can't removed the 7805 regulator from the Arduino board.

Why not?
Just cut the pins with a diagonal cutter.

Is there anything bad that could happen if I just wired the switching regulator in parallel?  As in, switching regulator 5v out -> Arduino 5v out pin, GND -> GND, Vin -> battery?

If the old regulator output is shorted (more or less) to ground, you mean?

Cut the bugger.

[rbtying]

Good point... I'll just cut the pins and dedicate the other supply.  7A regulators are much nicer =).  It's not like this particular board will be used for anything else.  I'm guessing the solder joint on the side without the 3 pins is the heatsink tab, and not actually important?  So I can just cut the three pins, and be done with it.  Thanks Soeren! 

[Soeren]

I'm guessing the solder joint on the side without the 3 pins is the heatsink tab, and not actually important?

The metal tab on the 7805 is connected to pin 2 (the middle pin), i.e. the ground connection, but that won't matter if pins 1 and 3 are cut.
I guess you ask because you just want to leave the broken regulator sitting there? If that's the case, just cut the pins as close to the housing and to the PCB, to make sure you won't have any shorts (you may wanna save a stub of pin 3, for connecting to the new supply.

[rbtying]

Yes, I wanted to keep it there and not fiddle around with a cheap soldering iron on an expensive board.  I'll cut them close, thanks.