Power Arduino2009 with external DC while using USB

I all, I'm developing a small energy data logger project based on Arduino2009. I'm now evaluating if using USB for data comunication or use serial (by an external MAX232).

USB could suit my need and I could even power Arduino through USB but during the night the computer connected to Arduino will be shutdown leaving the USB interface without power. So my question is: - can I provide external power supply to Arduino2009 while having it connected to a computer using USB (this connection will also provide power to Arduino)? - will Arduino remain powered when the USB interface will powered off? regards Luca

  • will Arduino remain powered when the USB interface will powered off?

Yes it will. Actually if both the USB and external power are active the board will draw power from the external power.

Lefty