Duemilanove Power

I am a bit confused. I am trying to figure out how to power the arduino duemilanove. I thought that I could just feed a 9v supply to the VIN pin, but then this from the duemilanove overview page got me confused:

5V. The regulated power supply used to power the microcontroller and other components on the board. This can come either from VIN via an on-board regulator, or be supplied by USB or another regulated 5V supply.

Does this mean I need to connect the Vin pin to the 5v pin somehow? Or is it already built into the board?

You can use any one of the options mentioned:
9v through the Vin pin
Regulated 5V into the 5V pin

In your case you just need to connect the 9volts dc into the Vin pin

Actually the best way to provide 9vdc power is through the external power jack as that route provides a polarity protection diode, after which it is called Vin and also wires to the Vin pin. The Vin pin was actually designed to allow you to power things external to the board that requires more then +5vdc, however it will work as a voltage input also.

As far as the Arduino wording on power, it’s trying to say that the components on the board all require +5vdc. This can come from either the USB connector (as it is already regulated at +5vdc coming from your PC) or external power (or Vin pin) which is wired to the input of the on board +5vdc regulator chip.

That any better?


Ok, thank you for the clarification. So the Vin pin can be input or output? hmmm…

I am hoping to turn this arduino into an ipod controller/ rgb LED VU meter. Do you think I will be able to do this? (16 rgb LEDs, + ipod serial control) or is there not enough power with just one duemilanove? Will the power for the LEDs come from the board, or an external source?

Ooh, I found this RGB LED shield, maybe this will be perfect for what I want to do. Any thoughts?

I don’t think the arduino onboard regulator can cope with the current required to drive all those LEDs, you will probably need an external 5 volt power supply. See if you can find out what the maximum current is for that board.

So the Vin pin can be input or output? hmmm…

No it’s only an input.

If you want to connect an extra power supply see:- Power & Heat

No it’s only an input.

Why do you say that? If power is being provided through the external power jack then the Vin pin can certainly be used to provide that voltage externally to say power an LED array of other load needing higher then +5vdc. I continue to say it can be used to input voltage or source voltage depending on how the board is being powered.


Why do you say that?

Because if it is operated in this way it is not an output it is simply a distribution point. That is it is the same voltage as you are putting in.

“No it’s only an input.”

Ok, it’s a power distrubution pin that can either input voltage to the board or output voltage from the board depending how the board is being powered. It cannot be said to be “only an input”.


It cannot be said to be “only an input”.

I think we are splitting hairs here and probably I am being the more pedantic. But then I am Grumpy. :wink: