How powerful is the output from Arduino Nano?

As a preliminary evaluation for planning Arduino control projects, I thought of looking at the output voltages and currents available from Arduino Nano. Digital output pins of Arduino Nano provides 5V output in high state and 0V in the low state. You may remember my old post in which I used an example sketch to make the built-in blinking LED on the Arduino Nano to blink at varying speeds. The LED will light up in the high state and go off in the low state. Maximum output current mentioned is 40mA. But it will be safer to use only 20mA to avoid damage to the ATmega328 chip inside the Arduino Nano. Hence if you are connecting an external LED to the Arduino output pin, use a current limiting resistor. Otherwise excess current draw can damage the chip and/or the LED. LEDs do not need 5V to glow, though there is some difference between different colours of LEDs.

5V pin on the Arduino Nano board can provide up to 500mA. But this is the combined power supply for the board itself and other low power components. Total current draw of all Arduino I/O pins combined is 200mA.

Here is a demonstration of the actual voltages in the Arduino Nano board being checked. Current drain from D13 pin when the external LED is connected is also being checked. It shows the variation in on and off states of the LED as expected during the functioning of the blinking LED sketch in Arduino Nano. Change in current between 330 ohms and 220 ohms voltage drop resistors are also shown.