I have a circuit setup that is similar to this:
(“button” tutorial from the Arduino website) http://arduino.cc/en/Tutorial/Button
but I don't use a pull-up resistor? Also, rather than lighting a LED as output, I send a message through the USB serial port.
When I close the switch, the Arduino board will power down. I attempted to fix this by connecting a 9v external power supply. The board does not power down, but now I lose my USB connection to my computer. Is this expected behavior? Does it have something to do with the fact that I don't have a pull-up resistor connected? I thought the resister was only there to ensure that voltage on the input was either 5v or 0v? (Forgive me if this is a stupid question, I don't have an electronics background).