LED Traffic Lights
Lights & LED circuits

LED Traffic Lights

By Bill Bowden


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).

LED Traffic Lights

6294 05 August 2007

See also:

Photo Electric Street Light
Photo Electric Street Light which receives input from a cadmium sulfide photo cell and controls a relay that can be used to switch off and on a street lamp at dawn and dusk.
3-6V Xenon Strobe Light
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40W Magnetic Ballast With Electronic Ignition
Here is the schematic of another fluorescent ballast circuit from a lamp I acquired along with the 80W electronic ballast. It actually contains a pair of the circuit in the diagram, one for each bulb.

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