Bit of an update for those who might be following: Ran out of wire in the middle of wiring up all the circuits. (Of course 26 awg wire is impossible to get locally so I had to order it. I also found some spade connectors to allow me to design the system so that if I ever have to move the layout I can separate the wires without making a mess. If the weather behaves, more wiring on Monday.
richhotrain Late to the party on this thread, and I have nothing substantive to add. But, for the life of me, I cannot visualize how the OP needs 12 sensors for the track plan in question. A posted track plan, even at this late date would help. I use Circuitron Grade Crossing Detection Circuits on my layout. I use them to trigger flashing light crossing signals. Far simpler than the OP's application since I use one sensor to turn on the crossing signals and one sensor to turn off the crossing signals. Rather than photocell or IR applications, why not use simple block detectors like the NCE BD-20 which work in the dark? Rich
Late to the party on this thread, and I have nothing substantive to add. But, for the life of me, I cannot visualize how the OP needs 12 sensors for the track plan in question. A posted track plan, even at this late date would help.
I use Circuitron Grade Crossing Detection Circuits on my layout. I use them to trigger flashing light crossing signals. Far simpler than the OP's application since I use one sensor to turn on the crossing signals and one sensor to turn off the crossing signals.
Rather than photocell or IR applications, why not use simple block detectors like the NCE BD-20 which work in the dark?
Rich
To answer your questions:
1) Need for 12 sensors: Three tracks sharing one crossing. With the Circuitron system (which I have taken out. see #2) each track needs four sensors. Three tracks times four sensors per track equal 12 sensors.
2) As already mentioned, I decided to change to the Logic Rail system with I/R as with those I can run "at night." The Circuitron system still need visible light to work. Admittedly, that doubles the wiring but it does what I want to do.
3) I don't run DCC. I decided awhile ago that I couldn't afford to convert to DCC. (20+ engines would get expensive.)
The cross track sensing is an option that I could have gone with but I decided putting it in the track would be seem to be easier. I did get the sensors installed yesterday as the weather was quite nice for March. I did have a few problems however: I had to move the sensor locations on the west end as they were too close to the framework. I also had to replace a couple sections of curve as I damaged some ties when I was drilling the holes for the sensors. Also reinstalled the ballast on those sections as well. We shall see what the weather brings as to getting everything going.
As to the picture question: I haven't found a good photo hosting site as the method I was using is no longer available.
You actually don't need beam-break to be reliable. You can use differential sensing. Haven't seen an off the shelf MRR product that does this, so today it's still roll your own, but there are some examples out there. There are two sensors for each location. One is located whenre it gets blocke, ie, between the rails. The other is located off to the side nearby where it doesn;t get blocked by the train passing by. The trigger is not when one sensor is blocked, it's when there is a difference in the light levels between the two sensors. So you turn on the bright room lights - no train, both read bright, train blocks one (mostly), there is a difference. Turn down the lights for night ops, both read low light, train blocks one, now one reads low light and the other reads no light. Or anywhere in between.
It's fairly easy to implement with an Arduino. It's also been possible for years with a comparator IC. The circuit and Arduino sketch are out there, but one of my projects in queue is to make my own. The little 8 pin ATTiny seems perfect to make a sensor - two opto sensor inputs and a digital out to signal whatever will be controlled. And cheap.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
LastspikemikeWell, bear in mind that IR is light, technically. I don't know much about solid state sensors but IR and visible light are "the same stuff".
It is possible to recover electricity directly from EM -- radio receivers, Tesla's beamed power, mirror-machine fusion generators and powersats all do. But most of the solid-state detectors act differently; see the theory of photodiodes or phototransistors sensitive in the IR range of interest for more.
The advantage of IR in cheap crossing detection is that it is 'invisible' light that can be provided rather brightly even when a room is 'dark' for nighttime effects -- hence the 'zero lux' designation. There's still plenty of light, just at a wavelength human eyes are not sensitive to. (You could do the same thing with UV 'black light' at the other end of the visible spectrum but many paints and materials fluoresce weirdly due to the higher energy at the shorter wavelength...)
The 'better' option for track specificity, as noted in the Circuitron documentation, is to use a close IR emitting light source at the track. Instead of breaking a beam or 'shadowing' a detector from ambient IR, this uses the light reflected and scattered from 'something on the track' to trigger the detector. As great brightness (probably even an IR laser diode, now used probably in enormous quantity in fiber-optic communications devices, although serious precautions would need to be taken) can be used without interference, this represents a good approach to noncontact detection that does not involve track power or switching.
In my case when I ordered the Logic Rail GCP it came with beam break logic and Logic Rail sent me the replacement logic chip for reflective beam detection. I piddled around with reflective beam with horrible results and replaced the emitter and sensor and reinstalled the original chip and found that across the rails detection worked perfect.I began a new way of detection and have had a lot of fun hiding the sensors. When the tree trunks are painted and the foliage applied the trees even looking closely the sensors are very hard to see and I know where they are.The IR emitters and sensors that I use are not effected by external light sources. I just buy the regular 3mm 940nm off eBay, I’ve never had any kind of external interference to any of my IR detection. I now use both beam break and reflective detection, both work great. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
One thing about Mel's setup is that it is wired as an 'electric eye' where a focused beam is interrupted for activation, as opposed to the 'tube' detectors where it is reflection of a normally-undetected beam's light that triggers the circuit. (Or is he just wiring up photodetectors for ambient light, like that Gerry Anderson puppet-show episode where the land mine went off when someone shadowed it ...or the day got sufficiently cloudy... or night fell...)
That would involve additional care to shape the emitted light into an actual beam, with some combination of IR-transmissive refractive or reflective optics or a 'projector-beam' valance on emitter or receiver to cut stray light. The beam setup may also be sensitive to sunlight or room light with substantial 'red-end' or IR spectrum (such as incandescents).
The great advantage of the beam approach for the OP's situation is that only two receiver-detector pairs are needed instead of six to do a 'comparable' job. That may well be worth the extra effort to set the beams up.
I’m late to the party too but here’s the way I do single or multiple track crossings. I use IR detection and hide the emitters/sensors at coupler height across the track at an angle to prevent the IR beam from being intermittent between cars. Emitter or SensorMy crossing detector is a Logic Rail GCP but similar IR detection would work with any crossing controller.Use your imagination for hiding the emitters/sensors on your layout. I have hidden them in track side signal controllers, buildings, bushes, rocks and as in the pictures above, trees. I even tell visitors about the hidden beams and ask them to find them, most can not. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
Alton Junction
I finally came up with the funds to get the Logic Rail components as discussed previously. I also decided to order a bell module as well. Probably won't be until later in the spring until I get it installed. (A little cold in the railroad room to work at the moment. However that problem is planning to be investigated this spring as well.)
FRRYKid It seems, from everything I've read, that this would work in low or even no light conditions. I want to be able to run trains in low light or even the dark.
Note that there is a parallel to how the old "zero-lux" camcorders did their business. These had a CCD sensor that worked into the infrared, and a ring or array of "invisible" IR lights around the lens that would illuminate even a totally 'dark' scene. Note that this is NOT ambient-light amplification, or some sort of video technology that works in very low ambient light without noise. It is an analogue to the old kind of IR night-vision scope that used specially filtered automobile headlights as illumination sources.
Do not bother with broader-spectrum photocells in this application -- you've already specified the right technology. The only remaining difficulty is to adjust the different emitters on the several adjacent tracks so stray light from one doesn't find its way to actuate any detector there.
The methods you might use to provide an enhanced IR reflector under equipment might change a bit to help with a stray-light issue. Perhaps arranging small panels as a kind of corner or segmental-parabolic reflector? Or deforming a piece of material?
Pot adjustments would be for using multiple detectors in series, as I think you were planning (if that turns out to be workable), or for fine adjusting any situation that might arise from having multiple separate emitter-detector pairs in too close proximity.
It's fairly straightforward to auto adjust the ir detectors. One way (when using them with an Arduino) is to use the analog inputs, and make comparison measurements as part of the code.
Getting it to work REALLY well - that's the hard part.
Back to the Circuitron sensors - if they are indeed photocells and not IR as I suspected, then parallel wiring will not work - at least after a certain number. Parallel resistors result in a value less than one of the resistors (if they are all identical, the math simplifies down to Total Resistence = ohm rating of one/number of resistors. so 2 10K in parallel is 5K, 100 10K in parallel is 100 ohms. So if you put 4 photocells in parallel, the total resistance is 1/4 the rating of a single photocell - and probably outside the range of the adjustment of the potentiometer. It might work if it were just two in parallel, but not 3, or 4.
The App Notes in the Circuitron catalog show hooking up sensors for two tracks, wiring them in series. Series should work. But you will still have the issue of being able to operate them with the room lights off. For stable operation in all light levels, you need IR detectors.
Overmod ... relatively low adjustment-pot setting ...
... relatively low adjustment-pot setting ...
From what the instructions show, one doesn't even use the pot setting dials with the I/R sensors.
LogicRailTechIn our newest generation of products we use a more sophisticated method of infrared detection which reduces susceptibility to overhead light interference
Note that installing a small panel of a material reflective in the infrared under equipment that is to trigger using an emitter-detector pair would greatly improve the sensitivity, but have little effect on direction of ambient IR into the detector...
LogicRailTech Circuitron's products are all photocell-based. We offer photocell versions and infrared versions of our products. In our newest generation of products we use a more sophisticated method of infrared detection which reduces susceptibility to overhead light interference (i.e. false detections).
Circuitron's products are all photocell-based. We offer photocell versions and infrared versions of our products. In our newest generation of products we use a more sophisticated method of infrared detection which reduces susceptibility to overhead light interference (i.e. false detections).
I had been studying the I/R information on the site. It seems, from everything I've read, that this would work in low or even no light conditions. I want to be able to run trains in low light or even the dark. (Set up app controlled lights for that express purpose. Of course, a few of my kitbashed engines need to have lights reinstalled for me to do that.)
rrinker Circuitron doesn't make it very clear what their detectors are. Most detectors that just use 2 wires to the circuit are photocells, not IR. IR sensors typically have 4 wires - 2 for the sensor side and 2 for the IR emitter. --Randy
Circuitron doesn't make it very clear what their detectors are. Most detectors that just use 2 wires to the circuit are photocells, not IR. IR sensors typically have 4 wires - 2 for the sensor side and 2 for the IR emitter.
FRRYKidIf an IR sensor system is that hard to create, explain the top of page 6 of the instructions that can be accessed from this link:
When the train covers the hole, the scattered light from the IR source bounces off the undercarriage, and enough of it reflects back down into the IR-detector hole to make the device at the bottom conduct (or more precisely, lower its resistance or whatever enough that the connected circuit turns on).
Note that this isn't what I was talking about -- it is not directional. You could make a crude approximation of directional by putting two detectors in, either side of the IR light source, and then build a circuit that compares the order in which the two activate when 'something reflective is overhead'. That's not a very good circuit, but it could be made to do something reasonably directional much of the time especially if trains are slow.
Note how this is different from the crude photodetector on p.5, which is basically something that turns off when it gets dark above. There was an episode of one of those British marionette shows where some moron designed a land mine that activated this way -- with a variety of comically predictable consequences that were not at all funny to the potential victims.
If an I/R sensor system is that hard to create, explain the top of page 6 of the instructions that can be accessed from this link: https://www.logicrailtech.com/GCP2%20instructions.pdf
Those instructions seem simple enough to me.
FRRYKidThe opto-sensors need some sort of light to work. An I/R doesn't need light to operate as it uses a beam to detect motion.
The active doors use a beam, of a different kind of "light" (it is in the 'far infrared' technically, but more accurately in the radio spectrum) and it is reflection of this into a detector that is used to signal the door to open.
Infrared 'motion detectors' won't work without ambient light, either; the difference is that a principal 'light source' in the infrared is ... you, or parts of you. The detector compares how that light strikes an array of detectors, and continually re-considers that pattern; when it changes sufficiently, the alarm is triggered. Take away that emitted light ... or move more slowly than the detector discriminates ... and you might as well be invisible.
In a sense, any IR sensor that is used as a modal switch by a circuit can be considered an opto-sensor, just in a different frequency range or responding to a different power spectrum from one that uses white light, or sunlight, or some other range or combination of frequencies to prevent 'falsing'.
Sensors in most night-vision setups work just the same way, except there are a great many of them in a 'matrix' and the IR type sometimes has proportional response (the green kind uses avalanche light amplification, which is a very different thing but still counts as requiring photons of light input to work correctly) You can do something similar with crossing detection in determining which direction a shadowing 'thing' crosses a detector matrix, but this is far more complex (and expensive, and difficult to make) than simple little circuits for model railroad crossings... and not much more real-world effective.
(Now, technically you could build a crossing detector that senses "heat" from a model, and responds to it; you could use something like an IR laser diode down in a hole to 'illuminate' the underside of a model and use that for enhanced sensitivity. But even in these cases you need light to make the detector work.)
The active supermarket doors use a beam, of a different kind of "light" (it is in the 'far infrared' technically, but more accurately in the radio spectrum) and it is reflection of this into a detector that is used to signal the door to open.
In a sense, any IR sensor that is used as a modal switch by a circuit can be considered an opto-sensor, just in a different frequency range or responding to a different power spectrum.
rrinker I don't see how the Circuitron one is any different, they are the same type of photocell detectors. Without a light beam to be broken so there is a change in resistence, they won't detect.
I don't see how the Circuitron one is any different, they are the same type of photocell detectors. Without a light beam to be broken so there is a change in resistence, they won't detect.
I will disagree with you that Opto-sensors and the I/R sensors are the same. The opto-sensors need some sort of light to work. An I/R doesn't need light to operate as it uses a beam to detect motion. (Think the automatic doors at your local grocery store or the security lights in people's yards.) No, I'm by no means an expert. I looked it up just like everyone else. https://www.arrow.com/en/research-and-events/articles/understanding-active-and-passive-infrared-sensors and https://www.fierceelectronics.com/sensors/what-ir-sensor
rrinker Or are you using some other type of sensor than the ones Circuitron sells? That could be a problem as well, the circuit is designed for photocells.
Or are you using some other type of sensor than the ones Circuitron sells? That could be a problem as well, the circuit is designed for photocells.
As the system stands right now, I am using the brown ellipsoidal Opto-sensors that Circuitron sells.
I don't see how the Circuitron one is any different, they are the same type of photocell detectors. Without a light beam to be broken so there is a change in resistence, they won't detect. Or are you using some other type of sensor than the ones Circuitron sells? That could be a problem as well, the circuit is designed for photocells.
I made a boo-boo eariler. I have the DT-2 not the DT-1.
In looking at the Logic Rail system, I see something that I like as I want to put some night operations into my layout and the Opto-sensors don't work in complete darkness. Too bad I don't know a way to put some sort of I/R sensor on a Circuitron board.
rrinkerBut I wonder how many can be in series before it won't work at all.
As you add detectors in series, both the 'dark' and 'light' resistance go up. If the pot is not set in the range that can compare the two values reliably, the device will not function correctly. Now, the resistance difference between light resistance and dark resistance proportionally increases, which technically would make for higher discrimination as the total resistance increases. But if the aggregate 'light' resistance exceeds what the 'dark' pot range can adjust for, the board will never sense enough of a drop in resistance for it 'not to be dark': either the board will have its channel 'stay on' as if detecting a train, or the sensitivity even in strong light will be so fidgety that shadows or passing insects trigger the 'dark' response ... which as I recall was one of the early reported symptoms.
Be easy to test what the board can accommodate by connecting up a resistor decade box, and see what the resistance corresponding to points on the range of the adjustment pot(s) might be. That will give you a good idea of what combinations of 'dark' and 'light' tested sensor resistance would produce...
Well if you are using the DT1 - multiple sensors most definitely do not go in parallel. App note 104 and 105 show this, but for multiple mains, you absolutely need multiple DT1's for it to work realistically. But you could probably get by with having multiple sensors wired like App Note 104. But I wonder how many can be in series before it won't work at all. They show two in App Note 104. 4 in series may render it not operational.
Other option is to return it all and get the Logicv Rail Grade Crossing Pro, which handles one track AND has the flasher part, and then their add on detection boards for each extra track. The GCP is less expensive than the CIrcuitron DT1 plus the flasher board. ANd operates more realistically - more like the DT2 which is a lot more expensive than the DT1.
If you have to have multiple tracks trigger the crossing, that's the way it goes. Or put the crossing with flashers elsewhere where there is only a single track to cross. Or dump it all and just put a pushbutton on the fascia that you press and hold when you want the crossbucks to flash.
FRRYKidThe resistance was the same on a working sensor as the non-functional sensor.
Make a little table: number the sensors temporarily, and log what all their resistances are when covered. Then shine a light into each at a consistent angle and record their resistances again, for comparison. Any that don't show resistance going down when illuminated aren't working. Any that show infinite resistance no matter what the light aren't working.
My guess is that a couple of these may not show the same degree of resistance drop in light that the others do, but until we know that (and have the values for the specific components you're using) we're fiddling in the dark and need to see the sheet music.
As to the system question, I'm running DC.
As I really don't want to spend another $80 or so (Two DT-1s and a piece of track to hold the DT-1s.), I'm just about ready to take all the sensors and DT-1 out and figure out how to just use the flasher unit (FL-2) to light the crossing lights. (A pair of Model Power units.)
The C sensors have now decided that they want only to work intermittenly. I also checked the D sensor that didn't want to activate and I used every test I could think of with my electrical tester. The results showed me nothing. The resistance was the same on a working sensor as the non-functional sensor. The voltage came across the same as well.
I'm still not sure it's supposed to work as yuou are trying to do. Which unit do you have, and a sketch of the track would help.
The Circuitron catalog with application notes is here:
302CAT.pdf (circuitron.com)
App Notes 101-105 cover crossing flashers, single track and multi track. The multi track option shows using multiple DT-1 detectors feeding one FL-2 flasher. The only multi track option that uses only one detection unit is if it's a single track in one side, and a siding ont he other side, so there are 2 tracks one side of the grade crossing, and 1 track on the other side. That's App Note 105, and the sensors are NOT in parallel, they are in series. From SD which is the sensor common, the wire goes to the sensor on track 1, then to the sensor on track 2, then finally back to the detector S1 or S2.
Though if you are using DCC - I suppose you are using the DF-2 or DF-3? Of COURSE the instructions for those are not online, but unless it explicitely says the sensors get wired in parallel I'd almost assume not, because none of Circuitron's other optical sensors get wired in parallel for multiple sensors.
The DT-1 and DT-2 are really only for DC, because they use the track polarity to determine which sensor is the start and which is the stop. The DF-2 and DF-3 use additional sensors and a microcontroller to figure out which way the train is going based on the order the sensors are blocked and thus need no indication from the track as far as direction is concerned.
With the way the diagram showed how to wire, I'm not exactly sure how I would have used a telephone cable for this situation. With a lot of practice, I've gotten the hang of working with the 30 AWG wire. The wiring is not that much of a mess, especially given that I remembered to color code it. The control (A, B, C, D) are one color and the SD is another.