I am building a DCC HO layout with a lengthy double-ended hidden staging area that will not be visible from the normal operating area. I am looking for a simple technique that will easily and safely permit me to bring trains to a rest. I thought of a technique that involves the following:
At each end of each staging track, electrically insulate approximately 18 inches of one rail.
Separately power each of the insulated rails through SPST switches.
At a moderate-to-slow speed, pull the train into the desired hidden staging track while having the power of the far end insulated rail turned off.
Does this make sense? Can the idea be improved? Is 18 inches the right length for the insulated rails? Are there other techniques that I should consider?
I have a similar condition. I insulated one rail and used momentary contact buttons to power the rail. As the train comes in, i hold the button for power. Once in, i just release the button to kill the power.
As far as the 18" is concerned, as long as it is long enough to isolate the engine(s) then that is fine. Most of my consists are usually no more than two engines.
Most people use block detection circuits that light an LED. Not only would you know when to stop the train, you would know which tracks are occupied to prevevt accidents.
I use switched blocks. When I want to park a train in a particular area, I just flip a switch and turn that particular block off. I use DPDT switche wired to both rails. When the switch is turned off, both rails go dead.
SImple and effective. The length depends on how many locos you will attach to each train, and how many of them are powered. The problem with this method is that if your train NEEDS 2 powered units to move it, the first one will enter the dead section and the second will stall or spin its wheels continously, unable to move the train.
AN alternative is to combine some sort of detector, a simple photocell that gets blocks by the train when it reaches a clearance point is fine, and a spring loaded toggle or pushbutton. The operator has to hold down the toggle or button to apply power to the staging track. When the light comes on (or goes out - there are simple circuits that work either way), they can release the button and kill power to the entire track.
The problem I’m still seeing is that he has multiple staging tracks. How does he know which tracks are occupied after running for a hour or so? Although he can stop a train, it only takes one good cra***o wish he had block detection.
Depending on the type of locos you are running, you may experience jerky motion as each axle crosses the insulated gap. For a typical 4 or 6 axle engine, the wheelset will energize the block as long as it is straddling the gap. Similarly, an illuminated passenger car or caboose will pass current through one truck (if only 4-wheel pickup is used) or across both wheelsets (for 8-wheel pickup.) You can alleviate this effect somewhat by staggering the gaps.
The system I used on my just-dismantled layout (and will use again on my bigger and better redesign of the same operating scheme) relied on a normally-powered relay to power the electrical section under the entire train. Tripping the detector (a mechanical switch) broke the relay power circuit. When the relay dropped out, the entire block was de-powered and remained that way until the departure sequence was activated. The same relay, different contact set, activated appropriate indicators on the control panel.
Had to do it that way, because some of my DMU trains are six cars long and have power cars in the middle and at both ends.
This is why photocells are good for hidden staging detection. Maybe 2 per track, at both clearance points, I’ve seen as many as 4. The outer pair are hooked to one indicator - as long as it’s on, BOTH photocells are uncovered and the train is definitely in the clear. The inner two (or maybe just one more) light up to tell you when you’re near the end of the siding. Stopt he train so the clearance indicators are on and the ‘stop’ indicator is on,a nd you knwo the train is not blocking anything other than the track it’s on. Duplicate this for each track.
Photocells work great in hidden staging because you don;t have to worry about ambient light - you can put bulbs above each detector. Used up top, they work great until you decide to have a night operating session - suddenly every block on the railroad is occupied.
How about a video camera? They are really quite cheap now. You can get the small ones for 30 bucks on eBay, and all you would need after that is a cheap old black-and-white TV set. You might even go to a video repair place and find an old camcorder with a broken tape transport mechanism - still works fine as a camera.
I’m in the process of building an infrared detector to activate a bulb in my (yet to be built) engine shed. When the engine pulls in and parks, it breaks the infrared beam across the tracks and a light comes on so the workers inside can see what they’re doing. Down the road I’d like to have some hidden staging and would probably use these detectors to known when I’ve cleared the throat and to know when I’m near the end of the track. This might be an option for you to consider. The parts are pretty cheap at RadioShack (and probably cheaper still online). I think with infrared, ambient light levels are not a big concern, unlike with photocells which depend on it. The upside of photocells are they are much easier to hide, but in hidden staging that isn’t a concern. When I get around to soldering it all together (might be a while before I do), I plan to post pictures of the end result (btw, I’m not electrically savvy and didn’t design the circuit; I found the design online).
Thanks for the affirmation of the concept, ideas on how to improve or vary it, and thoughts on other techniques.
I am going to consider grumpybob’s idea of using momentary contact buttons instead of SPST switches.
Why did you do this rather than a SPST switch wired to just one rail?
What distance would you suggest staggering the gaps, a little more than the length of a three-axle diesel locomotive truck?
This sounds like a real limitation of photocells. I suppose that this has been folks’ experience generally?
For the ideas on block detection circuits, photo cells, relays, and infrared detector, where could I read more about these techniques? Are there any web sources? Kalmbach has several electrical books? Which one covers these techniques best? My track center spacing is 2 1/4 inches. Will photo cells and infrared detectors fit in at least between my tangent
Here is the site from which I got the IR detector circuit: http://www.mrollins.com/irled.html
The current version of the RadioShack IR emitter/detector set basically looks like two LEDs , so if you can fit two LEDs, each pointed at the other, accross from each other on either side of your tracks, you can use this. I’ve built the circuit on a breadboard using the RadioShack parts identified (except for the regular LED, I already had one of those) and it works well. If you want to see a picture of that, let me know and I can try to post it. Also, I’ve pretty much mapped out how to put it on one of RadioShack’s pre-printed circuit boards. If the components fit as I believe, four of these detector circuits could fit on one pre-printed board.
Usings a photocell and an LED makes the most sense, as everyone said. I would make it atleast 5 inches from the turnout so you have a little leway on when to stop the train when the LED comes on.
I have the exact same hidden staging located below the layout and basically out of sight. There is the mainline and two sidings on an ell shaped shelf with a total track distance of about eighteen feet.
I to had to figure out how I could tell when a train entered the staging are and when it was clear of the arrival switch (read turnout) but not yet at the departure switch.
I decided, as others have mentioned, IR detectors. I purchased two on e-bay for six bucks each and installed them on each end of the main line about nine inches from the switch on each end. I wired them to a control panel and I used red LEDs on a track plan as my occupancy indicators. The control panel also has DPDT’s and LED’s to control the siding switches. This worked well and I then bought four more for the sidings
I run a train into the staging area and run it to the the far IF detector on the track that I have selected. This allows me to run a second train into that same track (length permitting) until the IF detector goes out. So far ever thing is working as planned.
The only problem that I have had has not been with the lay out or any part of it. the problem at times has been my memory. I know there is something there. The IF detectors tell me there is some thing there. The question at times has been what? old age is a humbling experience.
Is the staging area not visible because of a backdrop or other view block? If so, any chance of mounting a couple of mirrors over the staging track? This is what I’m thinking of doing once the viewblock is installed in front of my staging area. My layout is DC so controlling power to the staging tracks with switches is simple and barbaric.
I found this article which talks about using IR detectors instead of light detectors. IR is not affected by low light conditions and would be suitable for night operations.
I would imagine Lenz’s assymetrical DCC would work great for something like this if you do not have many decoder equiped locos yet. Many newer decoders can use the technology.
Otherwise, any type of detection circuit set up to detect when the train enters the last part of the block and kills the power to the entire track will work fine.
I would not do what you suggested if you ever run lash ups or consists. With the last section of track dead, the lead loco will loose power and the trailing locos will then be pushing the lead loco. This is hard on the couplers and if the trailing locomotives stall, then those locomotive’s motors will still be drawing power. I don’t think it is too good for the motors (although this may not be a problem as Tortoise switch machines do exactly this).