Need some advice on activating RR crossing lights. Not looking for any complicated computer type stuff just some good old school method of turning on the crossing light before the train reaches the crossing and then turning them off once the train clears the crossing. So far, I have come up with two methods to activate the crossing lights, Photo cells or infra red. What I need to know is how to turn them off once the train has passed. One way would be a timing device but that doesn't adapt itself to different train lengths. I would like to use the same system for both trains as well as trolley/traction as I plan on having both. Ideally it would function like the light in the stairway in my house that can be turned or off by either of two switches, one at the top of the stairs and one at the bottom. Any ideas?
You can get exactly what you want with the Logic Rail Tecnologies Grade Crossing Pro. I have 3 grade crossings operated by GCP's and they've never given me any problems (I even have custom operating gates). They have infrared or photocell versions and the logic will do all the things you described. You may need to have more than one GCP if more than one track goes thru a crossing (they can be daisy-chained together for this very purpose). They are also incredibly easy to install. No need to reinvent the wheel!
To demonstrate the GCP's capabilities, here's a video of one of my crossings in action... The gates have since been adjusted to go higher and run smoother. They are operated by a Tortois Machine that they GCP drives.
Thanks for the referral. It would appear to resolve my issue but, unfortunately, it is out of my budget range. I'm now looking at a low cost system involving some reed switches that may possibly work, I hope.
Inkaneer, Take a look at the Circuitron web site. Their DT2 may be what you need what you need for a bidirectional grade crossing with detectors and lights for any length train. They also have a detailed catalog on the website with application notes that may also give you ideas for homemade solutions! Tonkphilip
Simplest solution is adding an IR emitter and sensor to either end of the length of track that the crossing is on, so that when a train is blocking the line of sight the gate comes down. However, I don't know how far apart they can be (Azatrax limit is 18 inches but my garage door has them 20 feet apart).
Well, I think I made some progress in my endeavor to have a low cost, old school solution to my RR crossing idea. However, there remains a problem area. I plan to use magnetic reed switches to power very briefly an old Atlas snap relay. The relay will send electrical power to a flasher unit which will power the crossing lights. A magnet in the locomotive will activate the reed switch and start the process. So here is the problem. To turn the lights off after the train has passed the crossing will require another reed switch after the crossing and a magnet in the caboose (yeah, I still use them) to turn off the snap relay. So how do I keep the magnet in the locomotive from turning off the crossing lights before the entire train has passed the crossing? I'm thinking that maybe positioning the reed switches to opposite sides of the track (along with their corresponding magnets in the locomotive and caboose) may be an answer but I don't know how close a magnet must be to activate a reed switch. Any ideas????
Depending on the fidelity you want with real trains and crossing signals (e.g. different length trains; trains that may, during switching moves, only partially occupy the crossing signal zone, before backing out the way they came; modern ops without a caboose, etc.) you would need to know when anything is occupying the crossing zone on either side of the crossing. Thus, optical sensors would seem to be a major benefit, since they don't require any modification to the locomotives or railcars. You could probably cobble up something with an Arduino-type board if you are at all coding-capable for not too much $$. Or drop the coin on a solution from Logic Rail Technologies, et al. Note that unless you have optical sensors spaced no further apart than the shortest railcar, even they will not catch all possible conditions that a track-current-sensing solution can (assuming DCC, not DC, since the former always powers the track at a detectable level, and at least one resistor-equipped axle per railcar in your fleet.)
I have been using Azatrax IR products with good results. I use them to move turnout points on 2 reverse loops, to trigger automatic sequencing in a staging yard, and for a grade crossing. I also have some of the sensors out 12-15 feet from the control board with no issues. After trying to make my own grade crossing setup I just found it easier to use the Azatrax grade crossing controller to activate the lights and sound. There is an IR sensor set on each side of the crossing. First IR sensor set the train hits activates the circuit, then stays on as long as the train is over either sensor.
The best way is IR sensors. They work in all lighting conditions, where photo cells will activate when the room is dark. That being said, there are 2 methods to accomplish this task. 2 or 4 sensor methods. The 2 sensor method is by far the simplest and you space the sensors at a given distance and the lights activate as the train passes one, and turn off after it leaves the other. The problem with this method is long delays after the train passes. So that being said, there is the 4 sensor mode. This is a bit more complex but more realistic. You would have 2 sensors at the activation point which would be far from the crossing and 2 sensors close to the crossing for the deactivation point. The first sensor trips the lights and as the last car crosses the deactivation sensor it will cancel the lights much sooner. It becomes complex when you need to delay the deactivation of the far sensor on the opposite side so it doesn’t trip thinking a train is coming from the opposite direction. Arduinos can handle this job easily as well as some and gates if you wanted to do physical logic over software logic.
Thanks for the responses. I think I may have stumbled onto something using magnetic reed switches. The critical issue is how close does a magnet have to be to affect the reed switch. Obviously, this will depend on the strength of the magnet but somewhere in the cobwebs of my mind where all the good stuff I learned in high school physics class is stored I seem to remember that the magnet must be pretty close. I need to know that distance and therefore some investigation and experimentation will be necessary.
The biggest problem with using magnets is this. First there needs to be a magnet in each train and trailing car, and each will have to be calibrated to the right distance, which drives the second issue. It will in some cases negatively impact the overall performance of the train. I know this from first hand experience with magnets and using them to pick up iron dust off a layout I rescued that lived in a machine shop. The cars with the magnets were having issues due to the magnets, especially after they got a little fuzzy, if the fuzzy wasn’t exactly centered. Just keep this in mind, where an optical sensor of some type wouldn’t require anything special in any car. The IR sensors I use for my tram layout are self contained and I hid them under the rails with just the tops of the LEDs visible (and barely at that). They work in all conditions, and with any tram I put on the rails.
Several years ago Shannon Crabtree did a video on controlling signals with toggle switches. I adapted the method to run a grade crossing signal using a toggle switch and a Dallee electronics flasher module:
Unless I am missing something I don't see this as a problem of any magnitude. I run cabooses with all my trains so having them equipped with magnets is not a problem. So too, all my trains have a locomotive on the front. Calibrating the distance from the reed switch to the magnet should be a once and done deal and all magnets would be standardized as to distance above the rail. Then it is only a matter of setting the magnetic reed switch the correct distance. Like I said before more investigation and experimentation is needed. The only real drawback that I can see at this time is my system will not accommodate two-way traffic on a single track.
Im not saying your reed switches won’t work, they will, they will just add other problems. As for the direction issue, if you are using an Arduino for the logic and the flash timing then the direction won’t matter, it will just be a couple extra lines of code to change which switch handles the flash and which handles the off.
Likewise, I'm not saying your system is bad but my initial post on this topic stated thusly: "Not looking for any complicated computer type stuff just some good old school method of turning on the crossing light before the train reaches the crossing and then turning hem off once the train clears the crossing." So, Arduinos are thus eliminated from consideration as they are not "old school". Maybe in a couple of decades they will be.
