The following are Low Power – Grade Crossing Flasher circuits based on the LM555 and LM556 timer chips. They are designed to drive Light Emitting Diodes but could be used to drive low current incandesent lamps.
Basic Flasher Schematic : In the basic flasher the power to the oscillator and LED’s are turned on and off by the control circuit.
Synchronous Flasher Control Schematic : In the synchronous flasher control the oscillator is running at all times and the power to each set of flashers is turned on or off by the control circuit for that crossing. This allows any number of flasher sets at different crossings to controlled individually and yet flash in unison.
Push-Pull – Crossing Light Flasher
The next circuit uses a dual timer in a Push-Pull output arrangement. While this circuit would be sightly more expensive to build, it would make the wiring of the actual flasher mount simpler as only two connections would be needed.
The flashers can be turned on and off by using S1 to control the power to the circuit or by using S2 to RESET the timers. Resetting the timers will make both their outputs go to a LOW state.
This next circuit shows a simple grade crossing flasher with enough current capacity to drive 12 Volt lamps with 2 Amps current draw. The circuit could be used for open house displays, etc.
The flasher is driven by an LM556 dual time configured in a Push-Pull arrangement.
The flash rate can be adjusted by varying the value of the 500K ohm variable resistor. The flash rate is calculated as being from 0.54 to 3.1 Hertz.
Visit Here for more.