I'm looking for a totally passive way to detect the presence of cars and locomotives at specific locations on my railroad, hopefully without any restrictions, such as "it only works during daylight hours” or “it only works on metal cars, not plastic or wood”. I've been told to attach magnets to the bottom of my equipment and place magnetically sensitive reed switches between the rails, but that's not passive, it requires an action on my part, the attaching of a magnet to my locomotives and rolling stock. A fully passive detection system would allow me to detect a visitor’s locomotives and cars without having to alter their locomotives or cars in any way. Am I looking for the impossible?
There are many ways to sense equipment at various locations. Most require some form of "action" to which you are opposed. The only thing I can think of that will sense rail powered, battery powered and live steam would be an IR transmitter/receiver system.
Tom Trigg
The Home of Articulated Ugliness
If you want something that's completely passive, then I think you're looking at some kind of IR system. South Bend Signals uses an IR emitter/sensor that detects a passing train by bouncing it off the side of the passing train to change the color of their signals or trigger their crossing gates, etc. It works rather well outdoors, which came as a surprise to me since IR-based systems are sometimes very finicky in sunlight.
Depending on what you wanted the detection to do, you could probably talk to South Bend Signals to see if they have something that might work for you already. Or, you could dissect one of their signals so instead of changing the color of the light on the signal itself, you could run the wires to your control panel where lights on that would change color based on where the train is.
Ralph, how would you design a "track circuiting" system to work in the garden environment? Some issues that jump out at me; (a) the track is used to carry power to the motor, thus any direct connection between the rails would cause a short, (b) the wheels are insulated (and often made of plastic) so to avoid those direct shorts and cannot carry power from one rail to the other, and (c) the distances involved are significantly shorter than what the prototype uses, thus the differences in resistance would be considerably less (though arguably not immeasurable). Remember, the requirement is that it be completely passive, so no modification to any rolling stock.
Later,
K
Doesn't "transponding" do this under DCC? As I understand it, With the Digitrax system the loco signals its location. It's totally passive, once you have DCC hooked up and decoders installed
OK folks, remember one thing, he is asking for a system that will work with whatever type of motive power his visitors are using. About the only thing that will work with "Analog" (track powered transformet controled), "Digital" (in what ever form or brand) "Live steam" (and whate ever control system) is the afore mentioned IR system.
I don't think there is a passive way--IR sensors do require setting up the IR sensors and they need something to trigger --I have some on my railway.
I'm sure that somebody, somewhere, makes a piece of software that reads movement on video and tracks it--either somebody in film animation or some defense contractor. Set up a video camera with a view of the whole layout, connect the video feed to a computer, identify the trains, and instruct the software to track the moving objects. I'm sure that's doable.
Still have to set up a video camera though
In looking at South Bend Signal's web site (www.sbsignal.com), they do offer an IR-based block detection system. Definitely worth a call to them to discuss whether it would do what you're after.
I don't know that there is anything that's totally passive, but maybe one of dallee's products would work for you ( http://dallee.com/signaling_equipment.htm ).
Okay, Ralph, what's it do? I see the track power inputs to it, and an output of some kind. But beyond that, I'm lost. I'm not being flippant--I greatly appreciate that you're providing a circuit that would seem to do what is being discussed. But a bit of discussion as to how it works, and how the outputs can be used to tell where a train is would help all of us in understanding the circuit.
I agree with the proponents of using IR. I think that an IR sensor which is in a fixed location can be housed (protected) from stray light so that it's very reliable. It then can sense the presence of any kind of loco or rolling stock. But remember that it will also sense the presence of a dog, cat, human foot, blowing leaves, etc. So no system that is affordable by the average modeler is going to be fool proof.
Walt
I use one of these Harbor Freight IR sensors in my barn. It works great. There is no reason it won't work out on the RR to detect when a train goes by. Just keep the transmitter close to the ground and point it at the track. You can easily turn it off when it's not needed. Can't beat the price either at only $14.95.
http://www.harborfreight.com/general-merch/security/wireless-driveway-alert-system-93068.html
Mark
M. Gilger - President and Chief Engineer MM&G web
Web Site: http://mmg-garden-rr.webs.com/
I thought of motion detectors too, but, I'm not sure it would work. Most of these devises operate on a multi-segment array that compares the temperature differential between adjacent segments. I'm not sure an electric train generates enough of a heat signature to trigger such a detector.
I believe that an IR transmitter/receiver mounted on opposites sides of a track segment might be better.
Have you had any experiance with South Bends crossing gates or lights? I have worked with Jim from South Bend and we are having difficulty resolving this issue. The issue is false detections coming from the IR track mounted detectors. They seem to go on and off by themselves. I have adjusted the sensitivity pots till they just barely detect rolling stock. The IR signal only extends about 2 inches above the track. Jim has worked with me on this issue but it has come down to some sort of IR interference. Any help out there??? This is a good product but it can be better.
Never worked with South Bends products but I've had a lot of experience with industrial IR detectors. Does SB's unit have a transmitter and a receiver or a transmitter and a reflector? I assume it works by having the beam broken by the detected object.
I believe it is a trans and receive. According to SB, it works by bouncing the signal off the object and back to the receiver/collector. Right now the detectors are mounted in the tracks facing up. All of SB's other signals work by facing out across the rails. I am thinking about trying to mount the detectors so that they work the same way. I am not familiar with IR technology so I thought I would reach out on the web for any past experiance with these signals.
I hope to be out running trains tomorrow, so I'll take mine out and see if it works. Report to follow.
I tested the Harbor Freight motion detector yesterday. It does an excellent job of detecting passing trains from about 3 inches to 10 feet. I tried it in 3 different locations and it never failed to detect. The conditions here were sunny and about 85 degrees. I was surprised it was able to detect when I placed it so close to the track. If your going to experimient with them, their model comes with 2 different channels. Maybe more, but in our store it's channel 6 & 7. So you can have two sensors working independantly.
That's great news for everyone/anyone who needs low cost detectors, I'm certainly going to try one out. I'm still surprised that a motion detector is able to discern the temperature signature of a G scale scale train.
My original thought was to use the receiver part of this sensor and somehow tie it into a sound card with sound of a passing train. I have not had time to dig in and see if it's possible yet. I think that will be one of my winter projects. I did pick up a second unit with a different channel.
Don't know if you have arrived at a satisfactory or successful solution to your problem, but this website is run by a gentleman who is very much an expert at train electronics, especially for G scale. Check out his article on automatic block control / sensors.
Its been a while since this thread was active and the block circuit that was posted seems to be gone. Could you post that again? I think it was Ralph's diagram...
Let me also make another possibility available - Proximity switches. There are some small ones available (not up on pricing) that are single point devices. Could be located low enough to count wheels if you wanted to do so. I will see if I can find out any additional information, or do a Google search, there are a number of manufacturers out there.
Bob C.
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