Each pin can provide or receive a maximum of 40 mA and has an internal pull-up resistor (disconnected by default) of 20-50 kOhms. The Atmega328 has 32 KB of flash memory for storing code (of which 0,5 KB is used for the bootloader) It has also 2 KB of SRAM and 1 KB of EEPROM (which can be read and written with the EEPROM library).Įach of the 14 digital pins on the Uno can be used as an input or output, using pinMode(), digitalWrite(), and digitalRead() functions. A 3.3 volt supply generated by the on-board regulator. This can come either from VIN via an on-board regulator, or be supplied by USB or another regulated 5V supply.

The regulated power supply used to power the microcontroller and other components on the board. You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin. 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). If using more than 12V, the voltage regulator may overheat and damage the board. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. The board can operate on an external supply of 6 to 20 volts.

Leads from a battery can be inserted in the Gnd and Vin pin headers of the POWER connector. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack. The power source is selected automatically.Įxternal (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery. The Arduino Uno can be powered via the USB connection or with an external power supply.

Atmel arduino uno datasheet