Triggering a Camera for Train Detection: Ideas and Resources

[footballxpaul]

What do you guys think would be the best way to trip a camera so that it goes off only for when a train is passing through it? Sorry I can't get anymore specific than that. I was thinking laser tripping device but was wondering if there is anything out there that maybe used that ya'll might know about. Any input is appreciated, include a website if you know of a product that I could look into. Thanks

 

[brewnog]

You can get light sensors which trigger the shutter on sudden changes in ambient light conditions. Get yourself to a photography shop and see what's what.

 

[Danger]

Is this a still camera, or a video recorder? If a still, then I assume that there is some particular part of the train that you want to photograph. That would complicate the matter considerably. For a simple trigger at the first appearance of the train, Brewski's idea is good, or you could adapt a sonar rangefinder to intercept an intruding vehicle. For that matter, you could just lay a small hose across the track and use the resultant air pressure to trigger your camera (similar to the way that old-fashioned gas station bell systems worked).

 

[berkeman]

LOL. He's out there laying something across the railroad tracks, and gets tackled and wrestled to the ground by the local authorities...

Come to think of it, footballxpaul -- what exactly are you intending to do?

 

[footballxpaul]

I don't think the authorities would tackle a person who is on a team helping develop one of their systems. I most likely am going to a laser tripping device I just wanted some other ideas of maybe something I haven't heard of or thought of before. And danger it is more of a scan.

 

[footballxpaul]

You can get light sensors which trigger the shutter on sudden changes in ambient light conditions. Get yourself to a photography shop and see what's what.

actually this is the system they have installed already on it. It works ok, but it is always cutting off the ends of the scans

 

[berkeman]

I don't think the authorities would tackle a person who is on a team helping develop one of their systems. I most likely am going to a laser tripping device I just wanted some other ideas of maybe something I haven't heard of or thought of before. And danger it is more of a scan.

LOL. Okay, if you have access to the train line infrastructure, then you should be able to just use the train location sensors already in place, no? Do they use magnetic sensors to detect trains passing locations, or some other means?

Kind of like those sensors that didn't work too well in the rail crash in Washington in June... But I think they're supposed to be fairly reliable in general.

 

[Danger]

Do they use magnetic sensors to detect trains passing locations, or some other means?

As I understand it, at least in the old days, there was a small current running through the rails, which the train shorted. That was somehow used to trigger the crossing arms, probably by measuring the resistance. I never really heard much about it, though, and gave up trying to figure out how it would work.
A few things are coming to mind. Most of them are probably totally useless, but I'm going to toss them out anyhow.
One is that rails always sink into the bed under the weight of a train. A strain gauge underneath might work. Maybe a vibration/acoustic sensor on the side of the rail? Equip the trains with low-intensity radio transmitters? Upward-aimed photodetectors in the centre of the rail bed, so the hitches would prevent loss of signal between cars? Tie a chicken to the track, with a feather detector on the camera? Magnetic anomaly detector? Tap into a crossing-arm circuit?
I'm going to have to have a couple more beers and think on this some more.

 

[negitron]

As I understand it, at least in the old days, there was a small current running through the rails, which the train shorted. That was somehow used to trigger the crossing arms, probably by measuring the resistance. I never really heard much about it, though, and gave up trying to figure out how it would work.

For those who like to Google these things, those are called track circuits and yes, they're still used extensively even today.

 

[Danger]

Thanks, Negitron! I did just Google that. Only got as far as the Wikipedia article so far, but it sure cleared things up for me.

 

[MATLABdude]

For still cameras you can usually buy a remote shutter trigger which usually plugs in and causes the camera to take a picture by shorting out two connections (so you can rig up a relay or some such that does the same). Video cameras may have a similar functionality, or at least something you may be able to reverse engineer to control it via USB / IR control. If you're looking for a starting point on the second aspect of your project, that is.