Arduino power and ground questions

Forum 2005-2010 (read only) Hardware Interfacing
1

Correct me if I'm wrong but I just want to make sure I got this correct.
The arduino connected to a USB port will give you 5V max output.

But if you connect a 9V powersource you can draw 9V from the Vin pin? All other pins will ofcourse have their original voltage.

What about the max current of 20 mA for each pin? Does this only cover the digital and analog IO pins? Can I draw more current from the 3.3, 5 and Vin pins?

Is it correct that I shouldn't connect anything else to the arduinos ground pins except those powersources I already draw from the arduino? In retrospect after writing this I realize that every power source should have a output and a ground so to make a working circuit.

2

The Vin pin IS the power input pin, therefore the only thing that limits the current is the PCB tracks.
Each logic pin will source up to 40mA individually but there is a limit on how much in total they can source in total (I think it's about 200mA).
How, much you can draw from the 5V depends on the PSU volatge as it is limited by the heat dissipation in the regulator. For a fuller discussion see:-
http://www.thebox.myzen.co.uk/Tutorial/Power_Examples.html

3

Thanks for that link.. it seems to answer all my questions.