Arduino voltage supply

voltage supply to arduino uno can anyone tell me what will happen if i apply 3.8 voltage to 3 volt pin and 5 volt pin of arduino will work or will it burn the circuit cause i m giving external supply for my project do i have regulate my volatge

tenzin: voltage supply to arduino uno can anyone tell me what will happen if i apply 3.8 voltage to 3 volt pin and 5 volt pin of arduino will work or will it burn the circuit cause i m giving external supply for my project do i have regulate my volatge

Yes you will most likely destroy the regulators or the board with an unregulated input. The on-board regulators will regulate the external voltage for you but it needs to be applied to the Vin pin, not the 5V or 3.3V pins. It also should be within the range of 7-12V. 3.8V at Vin won't do anything.

Do not connect any external voltage to the 3.3volt pin.

You can connect an external voltage to the 5volt pin as long as it is lower than 5volt.
3.8volt (LiPo battery?) would be ok, but if you go lower than that, the Arduino might stop working.

Safer to use the V-in pin, but it needs >=6volt, e.g. 4 or 6 AA batteries.

An easy way, for mains powering, is a 5volt cellphone charger with USB socket.
Just plug your Arduino USB lead into the charger.
Leo…

thank you all

Have a look at this and you will learn how to power your Arduino and where the limits are: http://www.open-electronics.org/the-power-of-arduino-this-unknown/