This was the final project for my Digital 2 class. The project was to create a 4-way stop traffic light system composed entirely of discrete electronic components. Each set of lights represent the N/S and E/W directional lights. There are also two switches used to mimic sensors at each stop which detect if a vehicle is stopped at or going through the intersection. If a vehicle is stopped at a red light and no vehicle is detected from the opposing direction, the light will change from red to green. However, if there is a vehicle present at the green light, then the light will stay red. This is represented by pushing switches.
The system is driven by a 555 timer in astable-mode. The output is tied to a 74LM163 4-bit counter (16-count). The system is actually designed around a 10-count, but I didn’t have a BCD counter, so I had to NAND outputs Q0 and Q3 to the reset. The counter then drives a 7442 BCD decoder which controls the R/Y/G stoplights and is used to implement functionality of the switches.
The lights follow a sequence of 4-count green, 1-count yellow and 5-count red. As the light changes from yellow to red in one direction, the lights in the other direction change from red to green. Sorry for the fast count and quick comments, but running the counter slower would take much longer to demo.
The schematic can be found here:
https://imgur.com/Pawxj8U
I also created an ideal schematic designed with a BCD counter here:
https://imgur.com/3ubiw6D
Post time: Jun-16-2017