MODEL RAILWAY LEVEL CROSSING LIGHTS

CIRCUIT OPERATION

        The weight of the train operates push button switch positioned on the track. The trigger push button switch starts the sequence by switching on the amber light, a few seconds later the two red lights lit ON. When the train has passed the level crossing it operates the cancel push button switch which switches OFF the red lights and switches the green lights ON to allow cars to cross the railway until the next train arrives.

The circuit contain two 555 timer

1.  Monostable

2.  Bistable

        This project uses a 555 monostable circuit to switch on the amber LED for a few seconds. When this switches off it triggers a 555 bistable circuit.

1.  Monostable

        A monostable circuit produces a single output pulse when triggered. It is called a monostable because it is stable in just one state: 'output low'. The 'output high' state is temporary.              

                        

                    

Monostable operation

        Monostable mode: in this mode, the 555 functions as a "one-shot" pulse generator. Applications include timers, missing pulse detection, bounce free switches, and touch switches, frequency divider, capacitance measurement, pulse-width modulation (PWM) and so on.

2. Bistable (flip-flop) - a memory circuit

        Bistable mode or Schmitt trigger: the 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is used. Uses include bounce-free latched switches

        The circuit is called a bistable because it is stable in two states: output high and output low. It is also known as a 'flip-flop'.

Model railway level crossing lights is the circuit which designed to prevent cars from accident when the train crossing the road.

        This circuit allows car to cross the railway when green LED lights ON. When the train is coming it trigger the circuit through push button that placed a certain distance before the crossing level, amber LED lights ON for a few seconds and red LED lights ON that predicts the train is crossing.

        After crossing railway, the train cancel through push button, red LED lights OFF and green LED lights ON that allow cars to cross the railway until the next train arrives.