Traffic Lights

Hello again,

In this post I want to show you a project that I made while I was in 10th grade. It’s a set of four traffic lights, two for cars and the other two for pedestrians, located in the crossing of two streets. All of them are synchronized to work perfectly, even flashing when they are about to change.

The mechanism is a little bit difficult. It is a integrated circuit which uses a 555 timer circuit, a  HEF4020B 14-stage binary counter and an EEPROM memory. There are 10 outputs (10 LEDs, 3 in the car lights, and two for the pedestrian ones), all of which receive the state from the EEPROM, in which all the 64 configurations of each LED has been set.

To sum up, the 555 timer circuit generates a pulse which is slowed down by the binary counter and then, used in the EEPROM memory to change between the 64 different states. From the EEPROM the pulses are sent to the LEDs, all of which light accordingly.

In the integrated circuit can also be seen 6 LEDs which help to visualize the current state.

Here I leave you some images and videos to see it more clearly. You can find also the schematic of the circuit, the board and the Bill of Material. 

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