Crossing Light Indicator

Today many accidents occur because everyone is in hurry and we do not see the signal and crosses the railway line. So to solve this we can install this simple circuit which will give an red indicator when train is nearby and green indicator when train goes away from platform. For this we are using the reed switch as sensor.

An indication of red and green light is done with the help LED. You can also modify this circuit to use bulb in place of LED so that it can be seen from distance.

[[wysiwyg_imageupload:11093:]]

Fig. 1: Prototype of Crossong Light Indicator Circuit on Breadboard

This crossing light indicator circuit is based on two IC namely NE555 timer and CD7404 with few more discrete components. In this we are using reed switch as a sensor which come in two variety that is normally open and normally close. Reed switch is similar to relay. Like in relay, because of electromagnet field its coil energises similarly because of magnetic field nearby reed switch energises.

In normally open condition reed switch is open and when magnet is bring close to it, it become close. And in normally close condition it will remain closed in normal state and when magnet is bring near the reed switch it become open. In this circuit we are using normally open reed switch. For this circuit to work trains must have magnets attach to it.

In this circuit NE555 is configured in monostable mode. In this mode time delay of the pulses can be precisely controlled by an external resistor R1 and a capacitor C1. And CD7404 is a inverter IC which contain 6 individual NOT Gate on a single IC. Its outputs goes low when input is high. And its output becomes high when input is low that’s why it is known as inverter IC.

Now when train comes reed switch which is normally open state becomes close because of the magnet attach on the train which will trigger the pin 2 of IC1 and output pin 3 of IC1 goes high and RED LED becomes on to indicate that train is going to come. So that people may not crosses the railway line.

As soon as train passes away reed switch again come to its normally open condition as there is no more magnetic effect and pin 2 of IC1 goes low. Which will also make pin 3 of IC1 also low which in turn provided to IC2 which is a inverter IC and its output pin 2 become high and GREEN LED will glow to indicate that you can cross the railway line.