Hi All and thank you ahead of time for any and all responses. I have a pretty good size mountain with a double track going through it and it is curved so that you can not see through it. My plan is to have some kind of detection/occupancy system (not completely sure of the terminology) so that I can pull a train inside and park (hide) it for awhile and allow another train to go through the same mountain. I may even want to be able to uncouple the loco from the cars and use it elsewhere on the layout so the system will have to let me know when I have the train in the right position to do that.
Now at least a year or so ago, I went to a train show in Monroe WA and saw a guy that had made some kind of detection system that worked in light or dark and appeared to be real simple. I don't remember if it was just an infra red system or something else entirely. Don't ya just love getting old? WHAT?? Oh, it's time for my pill
sounds like you'll want several infra-red led/transistor type detectors to indicate presence at multiple locations within the mountain. Once you've figured out one detector, it should be easier to add more.
a combination of the circuits below could be your answer. Since things will be hidden, the led and photo-detector can be mounted above truck level on opposite sides of the track at a slight angle to avoid the gap between cars.
while the first circuit shows how multiple LEDs could be driven thru a single resistor, it shows an output, P1, that provides a high output signal when the presence of a car blocks the light path shutting off the photo-transistor.
the circuit below shows how an LED on a panel can be driven by a transistor when the input to the transistor is high. The path between the 2.2k resistor to Vcc that can be connected to the output, P1, in the above circuit instead of Vcc.
greg - Philadelphia & Reading / Reading
streetspookThank you Mel. I didn't even think about the need for the third detector. However, i think this suggestion like Greg's may be beyond my abilities. We shall see. Bill
Hi Bill:
I agree. The electronic circuit diagrams can be a little daunting.
If you want ready-made then here is one supplier who offers a variety of sensors. I have never used their products so I can't speak to ease of installation etc., but I have made my own detectors and installation was easy.
https://www.azatrax.com/ir-model-train-detector.html
I would suggest considering the MRD6T. It will give you six sensors which could be useful if you want to monitor both tracks.
I recognize that they are not cheap, however the completeness of the circuit (i.e. you don't have to provide a bunch of other components to finish the job) actually makes the price fairly reasonable IMHO. You can build your own IR detectors for very little money but adding in things like the variable delay can get complex as I'm sure you are aware.
Good luck with your project. If you want a diagram for a very basic IR detector I can provide one but you still have to build it yourself. Let me know.
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
If you want to detect the position of several trains in different places, the costs of using IR detectors starts to add up. You may find the most cost effective thing to use is closed-circuit TV. Harbor Freight offers a 2-camera system, full color/low light LCD flat panel display for around $75. Sometimes a picture is worth a 1,000 words.
Mike Lehman
Urbana, IL
If the OP is intending to uncouple a locomotive from a train in a hidden siding, I'd recommend television. So he can see what he's doing. Might be able to skip the detectors, too.
Ed
LION goes for the simple brute force methond. Him install a reed switch between the gauge, and magnets under the locomotives.
ROAR
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
Him also uses helper paws when soldering wires, it appears.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I think both sensors and CCTV have their place. For instance, having a simple signal light tell you things are right is less distracting than a TV screen.
But the weakness of sensors if that don't tell you much when things go wrong. A car can be derailed or uncoupled and the sensor would just tell you "OK" so lang as it's sitting over the sensor. Or the sensor indicates no occupancy, yet you could see on TV it's sitting right next to the sensor, but not in the field of sensitivity.
The fact that you want to use whatever you decide in order couple, etc is to me an argument for TV. Mel may have everything 100% reliable on his RR, but I can't make that claim (nor could the prototype for that matter. On the prototype, they did rely on signals, but the presence of Mark I eyeballs was also important. CCTV gives you a way to put your eyes where they need to be, esepcially on occassions where there is some doubt about the signal indication.
I have used this very device and one need not be an engineer to install
all six pairs of optical detectors and you can add additional LEDs for each detector--I added two additional for each detector-one flashing and one straight-screws to do this are on the board- plus the board has six LED lights built-in as well. Mine are buried inside a train station.
Funny you had problems with current detection with DCC. It's infinitely easier, because there is always power to the rails, so no need for a bia power supply to keep a trickle fo current flowing to detect stopped trains, plus you only have to detect one direction of current flow. Diode detectors (not good in DC or DCC, they cause a voltage drop) only need a single diode for DCC vs teh back to back pair needed for DC. DCC allows a simple current transformer detector (no voltage drop), if you build them yourself they can be like $5 per block, you can buy commercial ones at about $10 per block or less.
Current detection is better for block occupancy, much simplere than the extra circuitry needed to trigger optical detectors and reset them only when the block is clear - you could need up to 3 sets of sensors per block and still have a short power move. 'disappear' from detection.
Optical detection is better for spot detection - grade crossings, hidden staging to make sure the train is clear of the fouling point, etc. Those things are more difficult and complicated to do with current detectors.
Our club layout uses current transformer detectors and considering the layout is a sectional and is taken down and rebuilt multiple times in multiple venues, and travels in some enclosed utility trailers, the system is quite robust - rearely if ever requires any adjustments, just plug all the wires together between sections to get power, accessory power, cab bus, and detection system all linked up (an Anderson PowerPole connector plus a pair of phone cords) and it's ready to go.