Is this AC adaptor ok for Duemilanove?

The adaptor fits the Duemilanove jack, so that's good.

On the adaptor it says:

INPUT: 120V~60Hz 12W 0.1A
OUTPUT: 12V---500mA

I will be using the Duemilanove with an ethernet shield and an LCD to do essentially this:

except 1. the LCD has no buttons, 2. it will not be an email checker but will instead display content from my own online database, and 3. it will be powered not by usb but by an adaptor.

Will I be ok with that adaptor?

Thanks for reading!

Does it have the right polarity for the Duemilanove?

Usually there is a diagram showing the outer shell and the inner socket and which is + and which is -.

...and of course that's the one piece of information I left out.

It says "class 2" and right under that there is a diagram like the one on the top right here:

(with the minus sign, then a lollipop on its side stuck in a backwards c, then a plus sign).

I can't seem to find the correct polarity for the Duemilanove... do you know offhand?

Many thanks for you help.

I can't seem to find the correct polarity for the Duemilanove... do you know offhand?

Center pin is positive. The external power connector has an internal series polarity protection diode, so if you apply the wrong polarity there will be no damage, it just won't power up.

Lefty

I can't seem to find the correct polarity for the Duemilanove... do you know offhand?

The left hand picture, that's the one that has the '+' sign going to the center pin.

Don

So my adaptor which displays the diagram on the top right of that page will not work?

So my adaptor which displays the diagram on the top right of that page will not work?

If that diagram is on the adapter itself then it will not work.

Don

Crap. This is going slower than I hoped. Got any vibranium?

going by the picture you sent the link to, set the tip to +.. the coaxial connector of the various onboard Arduinos, (Uno, DUemilinove, Decimele, Megas, etc.. Excluding nano & stamp) is wired this way.

Despite a reverse polarity diode, it's still possible to over-power the diode, and cause it to either fail, or short. (if it fails, then 100% of the voltage is going right past it!)

going by the picture you sent the link to, set the tip to +.. the coaxial connector of the various onboard Arduinos, (Uno, DUemilinove, Decimele, Megas, etc.. Excluding nano & stamp) is wired this way.

That's what I was going to say until I realized that he doesn't actually have that type of reversible connector on his power supply. Read this part again: "So my adaptor which displays the diagram on the top right of that page will not work?"

Don

I think I may have found a suitable adaptor:

So now my question is: how do I change the jumper from usb to external?
At http://arduino.cc/en/Guide/MacOSX it says the jumper is "a small piece of plastic that fits onto two of the three pins between the USB and power jacks." Pins?
Is this the jumper, with the red arrow:

Am I tarded because I can't find instructions for doing this?
Isn't this kind of important? Shouldn't there be instructions, or if not, then how do I become someone who just knows what a jumper looks like and how to move it?

The duemilanove does the blinking led test with usb power btw.

The Duemilanove has no jumper, it auto switches from Vin to USB if Vin/2 is higher than 3.3V.
That adapter in reply #10 will work fine - at the worst you can cut the connector off and bring the +12V into the Vin header pin.

I believe your arrow points to the FET that gets turned on to let USB power in if Vin is too low.

That adapter should be fine.

You overlooked this part of the description of how to connect the board: "If you're using an Arduino Diecimila, ..."

Don

D'oh! So stupid. Mistook Diecimila for Duemilanove. Thanks for your reply.
I am starting to get the feeling that when my robots are complete, they too will be stupid. The only thing they will do is sit and cry to themselves. "Why did you program us to feel shame?" they'll ask.
This will be an excellent question.