
It is likely generally true for any Arduino based off the ATmega328 microcontroller.Arduino UNO is based on the Atmega328P microcontroller which is developed by which is an open-source microcontroller board. Note: This does not apply to the Arduino Due, and there are likely some differences for the Arduino Mega.

Therefore, if you have a 100 mA device on the 3.3V output, you need to also count it against the 5V total current.


However, this it also thermally limited, meaning that as you draw power, the regulator will heat up. When you are using an external power supply, through the barrel power connector, you are limited by the local 5V regulator, which is rated for a maximum of 1 Amp. This is shared with the devices on the arduino board, so the available power will be somewhat less. When you are powering your arduino from USB, the USB interface limits your total power consumption to 500 mA. As such, it can source significantly more power. The 5V pin of the arduino is not connected through the microcontroller.

However, depending on how you define the Arduino "Pins", this is not the entire story. total) current limit, and an per-pin limit: the analog and digital pins) have both an aggregate (e.g. The IO lines from the microcontroller (i.e. Basically, there are a number of limiting factors:
