Set Arduino Free!
You will notice that throughout the day, we had the Arduino connected to the computer via the USB cable. However, since we are using an external power supply, it is unnecessary to keep the USB cable plugged in for power purposes. To prove it, unplug the USB cable from Arduino and see what happens.
The last program that you upload should still be working. Even if you unplug the external power supply, the Arduino will remember the last program uploaded to it. Then, when it is plugged into power again, it will begin working! This is helpful, so that we can use Arduino in applications where we don’t want to be at a computer - such as in your final Pinball table!