Simulating a traffic light
This packet just shows how to use the Arduino to control several I/O pins in the same loop.
The project employs three monochrome LEDs, each with a different color: red, green,
and yellow. The code turns on one light after another in a traffic-light sequence.
Arduino’s Power Limit
If you built up this circuit so that it had 10 or more LEDs, you’d run in to the
problem that the Arduino can only produce a maximum of 200 mA on all the I/O pins (if they
are all powered on at the same time). For more info, see this article on
Arduino power limits.