Hi, this is my first post to the forum, a great source for solutions !
I am finishing a robot powered by a 9.6v Nimh battery. a LM317 brings this source down to 5v (1.5A max), that I use to power both the duemilanove (directly through the 5v Pin), and the sensors and servos.
My problem is that when I plug the USB cable in, mainly for serial debugging, the Arduino draws power from the USB, not from the external 5v (which is normal, as I understand it after reading this post, since there is no Vin - thanks BTW).
This is not a problem per se, everything works (maybe I was lucky), but the 5v from my USB port is in fact 5.06V, and fluctuates much more than my external 5v. This prevents me from having reliable sensor values on the computer.
In other words, I want the USB cable to transfer data, but not power. What is the best way to do this ? cut the red wire in the usb cable ? or cut a trace on the duemilanove ?
Thanks in advance :)
Manu (from France, sorry for my so-so english)