Diode D1 on the Duemilanove

Hi everyone,

I'm trying to integrate my project on a single board, which means that I want to have my circuits and the arduino on the same board. For this, I started from the Arduino Duemilanove schematics. Now, for recreating the Arduini, I need to order the parts, and I don't know which diode to use for D1 (it has no value in the schematic). I would use a schottky diode (DO214AA, 20V, 1A), is that correct?

And, additionally: can somebody explain me in some quick words how the automatic power-source switching works on the Duemilanove?

Thanks Arnuschky

Having made a few integrated boards myself, personally I'd start with something simpler than the Duemilanove. I use the RBBB as a starting point. Public domain, fully documented, simple :

http://www.moderndevice.com/products/rbbb-kit

Take a look at the Instructions at the bottom.

Why can't I find a D3 on the schematic for the Duemilanove ?

...because I meant diode D1. blush. Sorry, I guess I confused the numbers somehow.

PS: the duemilanove does not look overly complicated to me. There are a couple of SMD parts, but as I prefer that over through-hole anyway...

D1 is just a standard silicon rectifier diode. Any rated at 1 amp or more and 50vdc max voltage or greater will work fine. It's purpose is to prevent damage in case the external voltage is wired with the wrong polarity. It is not required if you can be certain you will never wire the voltage source backwards to the board, but it is cheap brain fart insurance. ;)

I'm not a real fan of the Arduino auto=voltage switching circuit. I think a simple SPDT switch or a 3 pin SIP pin jumper is much more efficient, simple and reliable as used in the Arduino Diecimila design. It gives the user complete control over what source should power the board rather then always allowing the external power to override the USB power.

Lefty

Thanks for your reply, Lefty.

Actually, I planned to remove the auto-voltage switching circuit. I mainly based my design on the duemilanove because of the auto-reset (and because I assumed there are other improvements on the updated schematic).

I removed the entire circuit around the LM358D (upper part in the schematic, including R10,R11,C11,C12 and T1), and its connection to the USBVCC (next to the USB connector). Did I miss something, our should this work as expected?

Thanks again Arnuschky