Hi. I am running a 3.3v Arduino pro, off 4.5v of aa batteries connected to VCC. Connected to this, there is a RFID scanner, that I am powering from one of the data pins. It draws 30ma.
Looking at the specs of the arduino they recommend max of 20ma - anything more will 'exceed the related specification' - And it does, because the voltage I am reading from this pin when high 3.5v....Which is not too far from the RFID's scanners spec of 3.3v. The overcurrent is dragging down the voltage, but this is exactly what I want it to do!
So. Everything works..... BUT, is this a good idea:
1) Does running an 3.3v Arduino on 4.5v matter? (as, from what I can tell, there is no difference between the ATMEGA chips for the 3.3v and 5v versions).
2) Might running an 30ma through a pin hurt it? - (the absolute max is 40ma....which the specs says may damage it if run continuously..... but this is 30ma).
3) I also power a 10ma LCD display on another data pin. Unfortunately this to also reading about 3.5v which is making the display contrast low as its a 5v display. connecting directly to 4.5v VCC makes it perfect, however I cant switch the entire display off through software then. It seems that the RFID scanner is pulling down the voltage on this pin also... any suggestions?