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Build Your Own 4017 LED Traffic Light Circuit Diagram
Description
This LED traffic signal circuit regulates eight light-emitting diodes – specifically, red, yellow, and green – for traffic flow in both the northern/southern and eastern/western directions. The operational sequence is established utilizing a CMOS 4017 decade counter and a 555 timer. The outputs from pins 1 through 4 of the counter are combined using eight 1N914 diodes. Consequently, the (Red - North/South) and (Green - East/West) LEDs are activated during the initial four clock cycles. The fifth clock cycle (pin 10) triggers illumination of both the (Yellow - East/West) and (Red - North/South) LEDs. The remaining clock cycles, spanning counts 6 through 9, are also combined using diodes to manage the (Red - East/West) and (Green - North/South) LEDs. Finally, the tenth clock cycle (pin 11) controls the (Red - East/West) and (Yellow - North/South) LEDs. The duration of the red and green signals is four times longer than the duration of the yellow signal, and the overall cycle length can be fine-tuned using the 47K resistor. The eight 1N914 diodes could be replaced with a dual 4 input OR gate (CD4072).
Circuit diagram
