After having understood about a traffic light controller and learned how to use a channel relay and how to expand Raspberry Pi GPIO, you are ready to build a traffic light controller.
For testing, we will build a traffic light controller for four road intersections with the following scenario:
First, we set all intersections showing the red lamp
To execute traffic light 1, we turn on the yellow lamp and then turn on the green lamp
After this, we turn on the red lamp on traffic light 1
Repeat these steps for traffic lights 2, 3, and 4
The following hardware is needed:
A Raspberry Pi board
Twelve lamps with four red lamps, four yellow lamps, and four green lamps
A 4 x 3-channel relay module
An IC MCP23017
Cables
In this case, you can ignore channel relay modules if you use a +3 V/+5 V LED, so LEDs can be connected to the IC MCP23017 pins directly. To simplify this demo, we use DC LEDs and don't need many-channel relay modules.
To implement our wiring, you connect all...