Schematic Rise

This is a schema of an educational interactive traffic, it uses a single Schmitt-trigger inverter IC (IC1a-IC1f) to directly drive three LEDs (red, green and yellow). When you call, the schema turns red for 30 seconds, then green for 6 seconds, then yellow for 3 seconds, then repeats the sequence.

Interaction of Light is provided by S1 which shortens the red to a period of just over 3s, if pressed while red is on.