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Optical Occupancy Detection for Eastern Route Staging

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  • Optical Occupancy Detection for Eastern Route Staging

    My two long (~30 cars) staging tracks are about 60% hidden behind the backdrop. I made a window behind a building flat so operators could see their train before it reached (and maybe shorted) the gaps at the east switch. And I rigged up a turnout position indicator in the upper floors of the same building, using a relay driven by a contact on the twin coil switch machine. But I didn't draw the whole circuit, so it took me a while to figure out what I'd done four years ago.

    I chose Rob Paisley's 8-phototransistor 'Inverting Photodetector' card. I ordered Orange and Purple LEDs from LED-Switch.com, so occupancy wouldn't be confused with signal aspects. And I chose a panel location where it could be seen from the south half of my attic. Here's the panel, masked and all but one hole drilled, ready for the final coat of paint:

    Saugus Staging occupancy display
    Last edited by jbvb; 01-16-2022, 10:48 PM.
    James


  • #2
    So what does the card do? How does it work?
    Home of the HOn3 North Coast Railroad, along the shores of Lake Ontario.

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    • #3
      The Inverting Photodetector has 8 places to connect phototransistors. which conduct electricity when infrared or visible light shines on them. And it has 8 connections for LEDs, each of which turns on when its phototransistor is dark ("inverting"). It runs on 12 VDC. Rob Paisley's long description is here: http://www.circuitous.ca/8PhotoInverting.html
      James

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      • #4
        Originally posted by David_J_Buchholz View Post
        So what does the card do? How does it work?
        Kind of works like the ones we both ordered off E-bay over a year ago. Remember?

        Bernd
        New York, Vermont & Northern Rwy. - Route of the Black Diamonds

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        • #5
          Nice choice, I had gone with the Circuitron BD-1 system years back. When you can't see where those trains are staged you need them.
          The biggest challenge, as you know is having super perfect track, because you can't get to the trains easy without crawl spaces and other obstacles.


          Louis L&R Western Railroad
          Pacific Northwest Logging in the East Coast

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          • #6
            I glanced at the BD-1, Louis; they have several features I don't need, and the lowest price I saw for a BD-1 is as much as Paisley's card with 8 independent sensors. The visible end of Saugus staging is easy to access. The rest is a hands-and-knees crawl with little headroom once behind the layout. The code 100 flextrack was laid more than 10 years ago and hasn't given trouble. Here's the schematic display panel in progress:

            Display panel ready for lettering

            The invisible railroad-east (towards Portsmouth) end is to the left. I need to show two things: First, where the train is relative to the left turnout:: Leftmost LED shows it's too close, the next LED's sensor is a foot from the first's. Second, at the center: where the ends of trains are so I can store two short trains on one long track. Again, the sensors are a foot apart.

            Occupancy LED wiring on display panel.
            I needed 9 wires from the Paisley card, so I used 24 GA solid for the cathode (positive) feed and Cat 5 network cable for each LED's operate lead. Telco color code puts Blue first, then Orange, Green and Brown. All the occupancy LEDs are orange - purple was a bad purchasing decision as they need 3 VDC where the orange lights on 2 VDC.The two unwired LEDs will repeat existing turnout position LEDs, once I figure out and document how I wired the existing ones. The block at the right end will anchor the cables.
            2 Paisley phototransitors ready to install

            Two of the phototransistors Paisley supplies, ready to be pushed into holes between the rails and wired to the control board. As with the LEDs, there's one common line but this goes to the 12 VDC ground. I have one more 4-phototransistor harness to wire and install, then I can start hooking the components up.
            James

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            • #7
              "First Light" was not the occupancy, but the switch position indicator repeater:

              Switch indicator lights working
              James

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              • #8
                I like the set up. Also wondering if the now ready availability of webcam type devices means there’s a video option to consider?

                I had a temporary 50’ LGB shuttle line set up with trains running from a staging area inside my garage through a tunnel opening crafted in a temporary plywood access door out to the street as a covid-distanced Halloween candy delivery system in 2020. Used a simple diode arrangement so that I could not overrun the end of the track out by the street and set up a web cam at that end which linked to a laptop inside the garage for me to monitor activity. Also had a buzzer set so that the kids could summon a train pulling a candy gondola. For what was very much a lash-up, it worked well. Just a thought.

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                • #9
                  Video would give an overview and answer a range of questions, but I'd need two cameras, one for each critical point. There aren't good camera angles; the ceiling is too close.. And the farther the viewer is from the display, the larger it has to be. A signal light conveys simple information quickly and effectively from a distance, and these LEDs are visible from anywhere in the south half of my layout. Of course, I'll find out what my operators think once the current wave of contagion passes.
                  James

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                  • #10
                    A couple of nights ago I got all the LEDs on the panel to light. The orange occupancy indications are enough brighter than the bi-polar red/green signal repeaters that the Red doesn't stand out. Both are fed from the same +/- 12VDC supply so first step is to see what dropping resistor Rob Paisley installed (his instructions show 1K ohm as typical). My red/green LEDs are using 470 ohm.

                    Panel with all LEDs lit

                    The next issue is making the occupancy lights go out. Eight resistors on the board set sensitivity, one per phototransistor. As shipped, the LEDs go out when I hold my CFL work light over the phototransistors. The rightmost sensors are indifferent to the 3-white-LED piece of light strip already mounted above them. Rob says 10K ohm is typical, I'll check what's actually there. Soldering is required because more sensitivity requires more resistance in this circuit...

                    The red 'ghosts' below the track are pilot lights on the power supplies for 12VDC LED light strips that are part of my layout room lighting.
                    James

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                    • #11
                      I planned to illuminate each pair of sensors with a 3-LED snippet of some old 12 VDC LED light strip I was given. I was hoping to illuminate the right (east) pair with an existing light, but that wasn't effective. I just installed a second snippet and that's bright/direct enough to work with Rob P's as-shipped resistor values. Next step is to install the 2 left (west) light fixtures and their sensors. Finally, I have to either relocate the rightmost LED light strip or add another, better situated. Photos when I have time, today was a lot of snow removal and registering my cars, tomorrow is sorting tons of scrap in a foot or two of snow.
                      James

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                      • #12
                        Any chance of showing the actual installation pics rather than the panel?
                        Also. Where did you end up locating the circuit board?
                        Home of the HOn3 North Coast Railroad, along the shores of Lake Ontario.

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                        • jbvb
                          jbvb commented
                          Editing a comment
                          The circuit board is screwed to an L-girder where it was relatively easy to reach and doesn't waste much wire. I could have saved a few more feet if I'd mounted it behind my spray booth, but not worth the complications working on it. I'll take some pictures behind the scenes when I return to working on it later this week.

                      • #13
                        The whole detector setup is for track hidden behind a backdrop, so I have to supply light for the phototransistors to detect. Here's a picture of the first"light fixture" I built:

                        LED light strip segment mount on wood block.

                        I cut the angle so it would clear the sloping ceiling of my attic. Weldwood contact cement attaches the LED strip to the wood block and the wood block to the Lauan plywood backdrop.

                        This one works fine. But when I tried re-mounting my older "see train through hole" LED light strip to better illuminate another pair of phototransistors, bad news. One phototransistor wouldn't detect its light at all, even if I held individual LEDs 1/4" above the phototransistor. The other one would admit the LEDs were 'light' but only when directly over the phototransistor. Both phototransistors accepted my CFL work light as actual light. So now I must make another 'fixture' and confirm its light works with its pair of phototransistors, then repeat twice more.

                        I expect the phototransistors with leads attached were assembled in Asia, and everybody involved only tested them under whatever "room lighting" was handy. They're said to work with infrared too, which I imagine a 5000K color temperature LED produces very little of. Hi, ho, if I wanted to sit and be entertained, the world brims with opportunity.
                        James

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                        • #14
                          That's interesting in a geeky sort of way, if I can say that without insult. I like your philosophical attitude.

                          Mike
                          _________________________________________________

                          Not everything that is faced can be changed, but nothing can be changed until it is faced. James Baldwin

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                          • jbvb
                            jbvb commented
                            Editing a comment
                            I know how to fix it, it's just more complicated than I'd hoped when I started.

                        • #15
                          That's interesting... Some LEDs are specifically designed to minimize light outside of their color spectrum (particularly UV, which can cause fading.) 3200/3500k lights are pretty easy and cheap, worth trying them...

                          dave
                          Modeling 1890s (because the voices in my head told me to)

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                          • jbvb
                            jbvb commented
                            Editing a comment
                            The non-blue light you see from most, if not all current White LEDs comes via the phosphor coating They modify the phosphor and lose lumens/watt efficiency to provide deep red or IR light, so it's quite reasonable that 5000K LEDs don't bother. Luckily I was given an old strip with cracked encapsulation and maybe 3500K color temperature. A chunk of that worked once, now to see if it will again.
                            Last edited by jbvb; 02-04-2022, 12:38 PM.
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