Problem on arduino

Hi all. I have a question for you, can I measure the V in output from 5v pin? Tnks All and sorry for my bad english

On Arduino Duemilanove (i guess on other models too): - from :

The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.

The power pins are as follows:

  • VIN. The input voltage to the Arduino board when it's using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin.

  • 5V. The regulated power supply used to power the microcontroller and other components on the board. This can come either from VIN via an on-board regulator, or be supplied by USB or another regulated 5V supply.

  • 3V3. A 3.3 volt supply generated by the on-board FTDI chip. Maximum current draw is 50 mA.

  • GND. Ground pins.

So, if you supply the board through the power jack, you can measure the voltage you're supplying through Vin pin, NOT the 5V pin. Hope that helps.

Vasilescu Thanks for your help. I have another question. If i don't have external supply (but only usb cable connected)the pin 5v run?

tnks :)

If you power it by USB, it will be around 5V since that is what USB supplies (mine is 4.8v on USB which is pretty typical).

ok tnks for you help me :)