Railroad Crossing

GlennH

Member
So I'm sitting at a railroad crossing waiting for the train to pass and I got to wondering ...

What kind of signal from the train activates the gates and lights?

Some kind of pressure sensor or proximity switch or what?


Probably not the right forum but I didn't know where else to post.
 

kwired

Electron manager
Location
NE Nebraska
Great link:thumbsup::thumbsup:

Not as many railroads near where I live anymore, but I remember when I was a kid the crossing signals would often be operating when there was no train anywhere close. People complained and even made fun of how stupid it was, but after looking through that information it is obvious the thing was designed to be active with just about any possible failure. General public does not realize this, but is better to have a signal and no train than to have a train and no signal.
 

Rampage_Rick

Senior Member
I've seen that before. Just about every time I sit at a train crossing I think about how the lights are wired in series, with that relay in the middle. Most of the crossings here use the "constant warning" method detailed on that site, where a signal is injected into one rail and the distance and speed to a train is measured by the signal returning on the other rail. As I recall it's around 15 kHz.

Around here they've switched many of the crossing bells to electronic units that look like this: http://en.wikipedia.org/wiki/File:Electronic_RR_Crossing_Bell.jpg

There's a new GPS-based control system being deployed called Positive Train Control. Essentially each locomotive will be equipped with an onboard computer which knows the location of the train and it communicates with it's neighbors via 220 MHz radio. I'm looking into some work installing PTC hardware.
 

kwired

Electron manager
Location
NE Nebraska
Cool indeed,

I think my brain would explode if i had to troubleshoot that setup
If you get into much controls this really isn't too complicated. You have to focus on smaller elements at one time, if you try to look at too much at one time you get confused.
 

sdbob

Senior Member
I spent some time a few months ago working on trolley platforms and Coaster crossings. It's a different world. Dropping a stick of emt across the tracks inside the detection zone will signal the gates and bells.
 

Stevareno

Senior Member
Location
Dallas, TX
I spent some time a few months ago working on trolley platforms and Coaster crossings. It's a different world. Dropping a stick of emt across the tracks inside the detection zone will signal the gates and bells.
When I was a kid, my grandmother lived near some RR tracks. I would often go and put coins on the rail so they would get flattened. :angel:

One time I found a chain along the tracks. Messing around, I laid the chain across the rails near the crossing and the signals went off. Scared the bejeezus out of me at the time! :eek:hmy:
 
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