Using LM7805 + onboard regulator

Forum 2005-2010 (read only) Hardware Troubleshooting
1

Hi...setting up my first Arduino. As the on-board regulator supplies a max of 400mA, I'm using a 10.5v, 1400mA wall-wart (~15v with no load), and powering from it both the Arduino (through its power plug) and a LM7805-based power supply which supplies a protoboard. Questions:

  1. Is this OK? In particular, if the LM7805 supplies (say) 5.2v, could that damage any of the I/O pins?

  2. Would it be better to power everything from the LM7805 and not connect the wall-wart to the Arduino power plug?

Regards,
ckin

2

if the LM7805 supplies (say) 5.2v, could that damage any of the I/O pins?

No it is OK. The data sheet says the input voltage on a pin should be no more than 0.5V above its supply voltage, so you have a bit of scope.

Would it be better to power everything from the LM7805 and not connect the wall-wart to the Arduino power plug?

Yes but only from the point of view of convenience and ease of use.