Hi, I am a totally new user for Arduino Duemilanove and I am doing my master thesis at present. My mentor gave me the board and I guess I broke the board yesterday. The COM3 disappeared from the device manager and the computer can not detect the board any more. (The USB port on the board became hot before that happened.) However the last uploaded sketch can still run properly and the board can still be powered by USB board or external AC adapter. The PWR, TX and RX lights are all on when the board is powered. I reported my mistake to my mentor this morning and he is curious about the reason. I also want to know because I do not want to destroy another board.
I think there are two operations I did may harm the board:
(1) I connected the board to the computer and AC adapter at the same time. So the board has both power supply source. (I searched the forum for this situation and there are different sayings about this.)
(2) I modify the circuit on the breadboard when the board is powered. (I understand I am so careless.)
At present I am eager to know which part of the board is broken and which operation of the two causes the damage. (I guess it's the USB port but I am not sure enough to tell my mentor.) And I also want some advice about the harmful operation. I really do not want to lose a good board again. :-[
Which pins was your sketch using?
Have you checked that XP hasn't done something annoying like bumping it up to another port? (I've plugged bluetooth stuff into my laptop in the past and ended up with 27 serial ports! My arduino is 27...)
Also have you checked that the port is enabled in device manager?
Thanks a lot for the suggestion.
I tried all the things except 3). (I guess the lead is fine because it still can power the board?) The result is no computer can detect the board. (I tried on 3 computers.) And the suspect port works well with other device. Is that mean the serial bridge has blown? Is that because I connect USB and external power supply at the same time?
Then what is the reason for the breakdown and high temperature?
That's what we are trying to help you determine. It's hard because there are many ways to cause damage. A wiring drawing of what you had and changed for external connections might be helpful. It sounds like your FTDI chip is toast, but the cause it not yet determined.
s that because I connect USB and external power supply at the same time?
It could be if the power supply that you connected to the board was too high. What voltage did you connect and how did you connect it?
In normal operation the Arduino Duemilanove as an automatic power change over circuit. However if you connected say a 12V supply to the 5V on the arduino then you could damage the serial / USB chip.
I guess the lead is fine because it still can power the board?)
No there have been several cases on this forum where the power connections are OK but the signal leads are not.
A wiring drawing of what you had and changed for external connections might be helpful.
I did the experiment according to Figure 4-6 in the book "Getting Started with Arduino". It's almost the same as the website http://arduino.cc/en/Tutorial/Button showed except the board type and input pin. (Mine is pin 7). During the experiment the button seems not work because the LED was always off even when I press the button. So I changed the circuit several times including removing the button, connecting pin 7 directly next to source wire [ch65288]which turn on the LED). And all of sudden the problem comes out. And I realize the board was very hot then. :-/
You may have over loaded/shorted the 3.3V supply mistaking it for the 5V supply. The 3.3V supply is very low current and is provided by the Serial-USB bridge chip (FTDI).
See if you can get 3.3V from the board (using a meter maybe?). If not, you may have blown the FTDI chip on the board. They are not expensive and I have personally removed and replaced them (though its certainly one the HARDEST things you might want do if you manually repaired a duemillenove.)
