level cross automation

[tisa]

hai friends

i have to do project on level crossing automation. please provide me with a circuit for it. wat i want is the level cross gate to close itself by detecting that the train is some were near and opening it as the train passes by. but there shouldnt be any duplication like closing of gate due to fall of a tree or something. please provide me with a quick help

 

[Boncuk]

Hi tisa,

how about an inductive sensor? It will react only if a certain mass of iron changes the inductance of a coil. These sensors are also used to control "on demand" traffic lights.

That kind of control ensures normal traffic flow and will switch from steady green to red only if there is traffic joining from a direction which is scarcely used for road traffic.

Boncuk

 

[kchriste]

Is this for a real train? Real crossing controllers work on the principle of the axles of the train shorting the two rail ties together. There are two basic types. AC and DC. The DC type is just a giant ohm meter and the rails have electrical breaks in them to isolate sections of track so it only triggers when the train is on the isolated sections. The AC type has a shunt across the rails maybe 1Km away at each end of the crossing. The loop forms part of an inductor which changes in value when the train is between the shunts.

 

[bunghole]

there is a page on wikipedia about how that works, but the page refers to signals to tell if the section is occupied, find that one, when the signal shows 'do not proceed', replace that with the flashing lights and bells. i've done axle resistance measuring before, and it's usually around 3-6 ohms, if that helps. usually, the is a fair amount of track before the crossing on both the up and down sides, but if there is a station on one side of the crossing, thats different.