can arduino digital pin current limit
This is a bit complex. Basically, there are a number of limiting factors: The IO lines from the microcontroller (i.e. the analog and digital pins) have both an aggregate (e.g. total) current limit, and an per-pin limit: However, depending on how you define the Arduino Pins, this is not the entire story. The 5V pin of the arduino is not connected through the microcontroller. As such, it can source significantly more power. When you are powering your arduino from USB, the USB interface limits your total power consumption to 500 mA.