Old Duemilanove vs. New Duemilanove: Power Output

I know that the older version of Duemilanove had power output 5V and 9V, the newer version has 3.3V and 5V. Why did they change it like that? Is it good for battery saving? In my opinion, if 9V is too much, then I can always use resistors...

To me the left one looks more like a Dicemillia (or whatever it is typed ;0)) yet not exactly.. strange thing. Anyone knowing older Arduinos or Prototypes might answer you that... It looks interestering though... yet i would guess that 3v3 and 5v are used as they are quite common on electronics whereas i never saw 9v...

edit on second thought this doesnt look like a real Arduino as it wouldnt be Shield compatible if you look at the power sockets.. maybe it IS some prototype or specialised one?

thanks! I am quite new in electronics, so i don't know how many Volts do the components need (leds, micro-motors, etc..)

I think I remember reading somewhere that the 9V is really just VIN, and they renamed it in a later version.

I agree that I have no idea which Arduino that left one is though..

A severe typo?

The version on the left looks like an "Arduino Extreme V2", one of the early versions having USB support. See http://arduino.cc/en/Main/Boards for a history lesson about all the boards.

The later boards did not get rid of "9V", but renamed it to Vin. 3.3V (and RESET) were ADDED to the power connector, but the old voltages stayed in the old positions.

um... wouldnt that mean that there is somehow a 9V source on the VIN :o :o :o ?

I think I remember reading somewhere that the 9V is really just VIN, and they renamed it in a later version.

That is correct. To be really accurate the 'old' 9v was not really 9vdc, but rather whatever the voltage at the external power connector is minus the voltage drop across the polarity protection diode. So if you were plugging a 12vdc power module into the external power connector then the 'old 9v' pin and the 'new Vin pin would both see about 11.4vdc. The current available on this pin is limited to the current capacity of the external power module and/or the current rating of the protection diode, whichever is less.

You can also provide power to the board by inputting a voltage (8-15vdc, the lower the better) to the Vin pin (or the old 9v pin) rather then through the external power connector. Both paths go to the input of the on-board +5vdc voltage regulator.

That older board photo is of the Arduino NG or Arduino Extreme v2 from the photos and schematics shown here: ( http://arduino.cc/en/Main/Boards ) Note the 4 pin power connector (+5,gnd,gnd, 9v) Vs the 6 pin power connector on newer boards (reset, 3.3v, 5v, gnd, gnd, Vin)