Hey, if i don't have a 5V power supply and need it to run one of my circuits on the breadboard, can I use the Vcc and ground on my arduino? Would it be a problem?
When i connected it, the value of Vcc dropped to 3.5V, why?
If your breadboard circuit consumes less than about 450mA (when run off USB) or 750mA (when run off the power jack), then that should be fine.
If the voltage drops, then you are either drawing too much current, or you have a serious flaw in either your circuit or your measurements.
Are you sure you don't use the 3.3V pin?
I think it is always best to have a separate 5v power source for external component that needs them. with 7805 IC it is very easy to add one and are its cheap.
Sometimes I just get 5v from one of my usb ports (in emergency or when I'm lazy). I sacrifice one of my standard usb cable disect it and just used the 5v and GND pins. I use the diagram here for the usb pin out USB - Wikipedia
jaydie:
I think it is always best to have a separate 5v power source for external component that needs them. with 7805 IC it is very easy to add one and are its cheap.Sometimes I just get 5v from one of my usb ports (in emergency or when I'm lazy). I sacrifice one of my standard usb cable disect it and just used the 5v and GND pins. I use the diagram here for the usb pin out USB - Wikipedia
You're better off using the Arduino's +5V than a USB cable like that.
The Arduino can supply about 450mA when powered from the USB, or about 750mA from an external power supply. If you draw power direct from the USB you are limited to just 100mA. Yes, some badly and lazily designed ports will let you draw more than that, but you risk breaking the port if you do.
and if you don't break the port... what effect will the extra current drain have on the rest of the circuit?
Doc
Topic (annoyingly) restarted here...
http://arduino.cc/forum/index.php/topic,110674.msg831330.html#msg831330