INTRODUCTION: This circuit is used to flash two LEDs alternately with equal intervals of time so that it can work as a model for rail road lights. Flashing led rail road lights focused attention of a driver during crossing railway tracks. This circuit is very much suitable for warning lights on a tall structure.
|Light emitting diode||Of two different colors.|
WORKING: This circuit comprises of 555 timer that lights up a set of traffic lights for a model layout. Both LEDs will have equal on and off timings. The 555 timer will have square wave at its output. This can be achieved by proper selection of resistors and capacitors. When output is equal to the supply voltage then first led will illuminate while in case of output at zero volts second led will illuminate. Hence, the switching of LEDs from one to another will depend upon square wave transitions from supply voltage to zero volts. The capacitor starts to discharge through resistor and eventually it changes state to start the cycle again. The switching speed of LEDs depends upon the values of resistors and capacitors which is determined by the period of square wave. With few enhancements more advanced railroad signal systems can be designed.
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