# Max current on vin?

Hi everyone! A question about the maximum current Arduino can supply!
I have an Arduino Mega 2560, and I know that each digital pin can produce (at maximum), 40 mA.
I even know that the total current should not exceed 150 mA, otherwise the board burns.
The question is: if I use an external input voltage (for example a transformer 12V, 2A, connected through the pinjack),
what current can I draw from vin? The limit is always 150 mA or I can draw the 2A from here?

Vin is linked directly to the input power jack. If you supply the board with 12V the voltage at Vin will be 12V. If the power supply can supply up to 2A then you can draw (board trace and board requirements aside) 2A.

Obviously, the board will take some of that 2A up, so you may only be able to get 1.8A at Vin (depending on the board and what it's doing at the time).

Also, at that kind of current rating, there is a good change that the board may melt. Not from any components over heating, but from the copper on the board itself overheating. For larger currents wider traces are required - the ones existing on the board aren't that wide, so they may start smoking.

You would be far better off taking the power direct from the input connection - add a Y splitter of some form to the input jack so you can take your feed direct from there. Either that or feed the power direct into your external system, then feed from there (via a diode - Schottky for preference) into Vin to power the board.

If you supply the board with 12V the voltage at Vin will be 12V.

Not quite, there is a series diode between the jack and the Vin pin, so you drop 0.7V. Also that diode is only rated at 1A so that limits how much current you can draw from it.

there is a series diode between the jack and the Vin pin

True... I only have an UNO to hand - I know the diode is there on the UNO, but didn't know about that specific model of Arduino to say if there was or not. Note I mentioned adding your own to Vin if supplying externally