I know I am stupid but I shortcircuited the +5V and GND line on my Nano. My eyes are not that great anymore so I made a wrong connection on my breadboard.
Anyway, ever since, my computer does not recognize it anymore.
In an old thread (http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1256229321
) I came across some people who had this problem as well and usually it is the Scottky diode that connects the Vusb with the 5V line: replace that and yr problems are solved.
Before I do that however, I had a few doubts and I was wondering if some people can maybe think along and give me some pointers.
- I measured (with a MM) the diode and it still seems to have a low impedance in conduction direction and a high impedance the other way, like one wld expect with an intact diode
- Nevertheless if I connect the USB, I measure 3 volts on the 5 V line (That line is directly connected to the kathode of the diode) and indeed 5V on the anode of that diode (which is connected to the USB supply line). 2Volts over a Scottky diode ofcourse is not OK.[\li]
- Power led is still working, the Tx and Rx diodes only briefly blink at power up
Just to be sure I tried it on a different computer, the same problem.
So I actually had 3 questions:
Is it indeed possible that a diode 'blows' in a way that it still lets through current but obviously with a much bigger loss in Voltage? I thought that if a diode blew it wld either let all current through or nothing at all anymore.
If it is the diode, how critical is it to replace it with exactly the same one. Wouldn't basically any Scottky diode be OK?
Could it be anything else?
If this was all normal size, I wld have tried already, but with 50 yr old eyes and SMD, that is not something I look forward to.
Just to be complete (in case someone else is looking for a solution), I add a link to a picture of the underside of the board:http://www.flickr.com/photos/allartburns/4225076075/
(hoover over the picture to see a note on the diode)
and here is the schematic of the Arduino nano:http://arduino.cc/en/uploads/Main/ArduinoNano30Schematic.pdf
My arduino does not look like that at all (a clone): In my case the diode is closer to the USB port, but as there only is one diode on the board, it should not be hard to find.
Your input is appreciated