Description
The LED traffic Light circuit controls 6 LEDs (red, yellow and green)
for both north/south directions and east/west directions. The timing
sequence is generated using a CMOS 4017 decade counter and a 555 timer.
Counter outputs 1 through 4 are wire ORed using 4 diodes so that the
(Red - North/South) and (Green - East/West) LEDs will be on during the
first four counts. The fifth count (pin 10) illuminates (Yellow -
East/West) and (Red - North/South). Counts 6 through 9 are also wire
ORed using diodes to control (Red - East/West) and (Green -
North/South). Count 10 (pin 11) controls (Red - East/West) and (Yellow -
North/South). The time period for the red and green lamps will be 4
times longer than for the yellow and the complete cycle time can be
adjusted with the 47K resistor. The eight 1N914 diodes could be
subsituted with a dual 4 input OR gate (CD4072).
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