Circuitron DT-2 crossing detection unit question

[Over50]

The PDF instructions show the unit wiring for (1) bi-directional crossing detection with using (4) optosensors.

I am running DCC engines and I have two separate crossings with signals (identified as crossing A and B) about 3 feet apart that trains will cross in either direction.

Question:

Is it possible to configure a single DT-2 for use with the two crossings with (4) additional optosensors for crossing B by essentially replicating the A crossing sensor wiring configuration?  

[rrinker]

 I suppose you could parallel another set of sensors, but it's just going to trigger the outputs the same - might as well just put the sensors on the extreme ends of the two crossings. Unless there is another path between the two that a train can enter/exit either A or B without passing through both. If a train entering A has to pass through B (unless it backs up), there's no difference using two sets of sensors or just using the single set and treating A and B as a single crossing.

                                  --Randy

 

[Over50]

rrinker

 I suppose you could parallel another set of sensors, but it's just going to trigger the outputs the same - might as well just put the sensors on the extreme ends of the two crossings. Unless there is another path between the two that a train can enter/exit either A or B without passing through both. If a train entering A has to pass through B (unless it backs up), there's no difference using two sets of sensors or just using the single set and treating A and B as a single crossing.

                                  --Randy

 

Thanks, Randy.

For explanation purposes picture crossing A as on the left and has a main line, a passenger station siding and a separate freight siding that pass through it. 3 feet from to the right is crossing B with a continuation of the main line and one track that's the start of a route to an upper level.

Trains enter crossing A and B from either direction.

I envision the need for an optosensor for each of the 3 tracks that traverse crossing A and then an optosensor for each of the 2 tracks that traverse crossing B.

As such I'm thinking of - but not sure it will work with one DT-2 - placing an optosensor in each of the 3 tracks that traverse crossing A and wire them in parallel. And then place separate sensors in the tracks that traverse crossing B and wire them in parallel.

[rrinker]

 So the siding and main at A make effectively a double track crossing, plus there is the extra crossing at B?

In any case, if you use a single DT-2, the flashers will trigger for both crossings no matter which one the train is actually approaching first.

Also you mentioned using DCC - so you need to wire the toggle switch and NOT connect the L and R terminals to the track.

They don't give any details - it MAY work with multiple sensors parallel, or it may actually require them in series. 

                                --Randy

 

[josephbw]

I have a related question. I have several areas that have multiple tracks at a crossing. Will the Circuitron DT-2 allow you to install the 4 sensors in each of the tracks and allow any of the tracks to trigger a single pair of crossing signals?

 

Thanks, Joe

[Over50]

rrinker

 So the siding and main at A make effectively a double track crossing, plus there is the extra crossing at B?

In any case, if you use a single DT-2, the flashers will trigger for both crossings no matter which one the train is actually approaching first.

Also you mentioned using DCC - so you need to wire the toggle switch and NOT connect the L and R terminals to the track.

They don't give any details - it MAY work with multiple sensors parallel, or it may actually require them in series. 

                                --Randy

 

 

Thanks again for the reply. I didn't see mention of parallel sensors either in the written wiring/operation description.

I understand NOT to power the DT-2 with DCC track power. I currently have the A and B crossing lights powered with a compact plug in 12vdc unit and operated manually with toggle switches.

Since I run trains in both directions on multiple tracks through the two crossings I'll just have to experiment with additional optosensors to initialize and turn off the crossing lights. At this point logic points to wiring them in parallel.... but.

I did email circuitron support but it was after close of business this past Friday. Assuming I get a reply I'll post back.

All said and done I'll probably end up having to speak directly with support to find out if it's possible to parallel the approach and exit sensors with a single DT-2

[richhotrain]

Over50

I did email circuitron support but it was after close of business this past Friday. Assuming I get a reply I'll post back.

Call Circuitron tomorrow morning. They will answer the phone which is even better than waiting for an email response.

Rich

[Over50]

Sorry about the delay getting back with the results of my contact with Circuitron.

Per the Circuitron rep who replied to my emails the DT-2 bi-directional function is dependent upon track polarity in it's operation. Or, simply put, it's designed for DC layout operation. To adapt it to DCC operation requires the use of a toggle switch with the module... which totally defeats fully automatic crossing signal detection.

I explored motor current sensing modes of signal operation but for bi-directional operation with a double track configuration the cost is prohibitive... for me at least.

Once your needs evolve beyond a single direction of travel through a crossing all of the train detection methods - opto sensor, IR, current sensing - become cumbersome to effect and especially so for bi-directional detection with two or more tracks feeding or passing through a road crossing.

With multi-track detection you get into solid state latching circuits in essence which compounds the complexity along with requiring deep pockets.

So..... I'll continue to manually toggle my crossing signals on an off...                  

 

 

 

 

[hon30critter]

Hi Over50,

Have you had a look at these guys? I have no personal experience with them but they were the first thing that popped up when I did a search. I wonder if the MRD8 eight channel detector might work for you? It is suited to DCC and seems fairly simple to install.

http://www.azatrax.com/ir-model-train-detector.html#current-sense

EDIT: I just realized that the website is showing most items to be out of stock. That doesn't help much. I wonder if they are still operating?

Dave

[Over50]

hon30critter

Hi Over50,

Have you had a look at these guys? I have no personal experience with them but they were the first thing that popped up when I did a search. I wonder if the MRD8 eight channel detector might work for you? It is suited to DCC and seems fairly simple to install.

http://www.azatrax.com/ir-model-train-detector.html#current-sense

EDIT: I just realized that the website is showing most items to be out of stock. That doesn't help much. I wonder if they are still operating?

Dave

 

 

Yes, I looked at the Azatrax detection offerings - with choices of opto-sensor, current detection and IR. Same issue ... once you get beyond bi-directional single track crossing signal operation the application of sensors regardless of type becomes cumbersome and expensive.

Spending upwards of $200 to $300 to achieve two and three track convergence at a single crossing signal operation in both directions is for people with deep pockets and a lot of time on their hands.

Everyone of these sensor options requires filtered power supplies, too, in order to work with the corresponding logic circuit boards.

[rrinker]

 It all comes down to, do you want it to work like a realistic grade crossing, or are you happy with having lights blink kind of at the right time? The type with 2 sets of sensors on each side don't need that direction toggle to tell it which way the train is coming, and they also respond properly if you stop short of the crossing and back up. 

 I wouldn't say the application of additional sensors is cumbersome - if you have 3 tracks then you are just doing the same thing 3 times, it doesn't really make it any more difficult. 

 Filtered power supplies are dime a dozen, you might even have spares if you don't throw away the wall warts from otherwise dead equipment. You shouldn't be hooking non-train running stuff to DCC track power anyway. If you're concerned about costs, a filtered power supply is cheap compared to a DCC booster.

 There's always DIY, an Arduino and a boatload of sensors won't cost more than $10 and you could do any number of tracks. Of course, you have to write the program to make the lights flash based on the sensor readings. 

 Then thre's always the other option - move the road so only one track crosses it.

[Over50]

rrinker

 It all comes down to, do you want it to work like a realistic grade crossing, or are you happy with having lights blink kind of at the right time? The type with 2 sets of sensors on each side don't need that direction toggle to tell it which way the train is coming, and they also respond properly if you stop short of the crossing and back up. 

 I wouldn't say the application of additional sensors is cumbersome - if you have 3 tracks then you are just doing the same thing 3 times, it doesn't really make it any more difficult. 

 Filtered power supplies are dime a dozen, you might even have spares if you don't throw away the wall warts from otherwise dead equipment. You shouldn't be hooking non-train running stuff to DCC track power anyway. If you're concerned about costs, a filtered power supply is cheap compared to a DCC booster.

 There's always DIY, an Arduino and a boatload of sensors won't cost more than $10 and you could do any number of tracks. Of course, you have to write the program to make the lights flash based on the sensor readings. 

 Then thre's always the other option - move the road so only one track crosses it.

 

Randy... I understand configuring separate opto-sensors to trigger the signals for the passenger depot track and freight siding track that converge to one track in the middle of crossing plus the main track that passes through the first crossing I dubbed "A".

The problem becomes the short distance between crossing A where these 3 tracks converge into (2) tracks and then through crossing B only 30" from crossing A.

I've haven't found any way on paper to trigger crossing B as the first crossing signal to trigger with trains running in the opposite direction, then shut off after the last car passes, then trigger crossing A signals, then turn off without the placement of the sensors for A and B crossing signals affecting them both.

What you propose as I understand it would work if I accept the signals at crossing B continuing to run until the last car passes through crossing A. And the same situation where crossing A signals continue to run until the last car passes through crossing B. 

[rrinker]

 WIth just one controller, they'll all have to operate at once, a train approaching from the B side will trigger A and B, and keep A and B going until the train clears the A side. Likewise a train from A will trigger A and B, and kee both going until the train clears B.

 Anythign else requires two controllers, one for A and one for B, with the sensors interleaved, such that the sensors that start B would have to be on the A side, but before the sensors that stop A. SO a train from the A side would tigger A, pass through the crossing, trigger B, and then as the last par passed some point between A and B, A would stop but B would keep going until the last car passed B.

The Logic Rail controller uses 2 sets of sensors on each side of the crossing, that way it can tell which way the train is going. The Circuitron controller is a much simpler device, with just 2 sets of sensors, and you have to somehow tell it which way the train is going, so the sensors on the approach side become the activate sensors and the one on the opposite side are the deactivate ones. The Azatrax one looks like it can be used either way, one sensor on each side, or two sensors on each side. 

 It seems liek what you need is somethign with multple sensors on one side (where there are more tracks) with just one sensor on the other side (where all the tracks have converged to just one). You really need to call one of the controller vendors to see what they suggest. They may or may not have the logic in them to do this. This would be a perfect DIY thing, because you can so that if th sensor on track 1, 2, or 3 is tripped, start the flasher until the sensor on track 4 on the far side is tripped, and if the sensor on track 4 is tripped first, activate the flashers until any one of the other 3 sensors is tripped, so it won't matter which route the train takes.

                                                  --Randy

 

[Over50]

rrinker

 WIth just one controller, they'll all have to operate at once, a train approaching from the B side will trigger A and B, and keep A and B going until the train clears the A side. Likewise a train from A will trigger A and B, and kee both going until the train clears B.

 Anythign else requires two controllers, one for A and one for B, with the sensors interleaved, such that the sensors that start B would have to be on the A side, but before the sensors that stop A. SO a train from the A side would tigger A, pass through the crossing, trigger B, and then as the last par passed some point between A and B, A would stop but B would keep going until the last car passed B.

The Logic Rail controller uses 2 sets of sensors on each side of the crossing, that way it can tell which way the train is going. The Circuitron controller is a much simpler device, with just 2 sets of sensors, and you have to somehow tell it which way the train is going, so the sensors on the approach side become the activate sensors and the one on the opposite side are the deactivate ones. The Azatrax one looks like it can be used either way, one sensor on each side, or two sensors on each side. 

 It seems liek what you need is somethign with multple sensors on one side (where there are more tracks) with just one sensor on the other side (where all the tracks have converged to just one). You really need to call one of the controller vendors to see what they suggest. They may or may not have the logic in them to do this. This would be a perfect DIY thing, because you can so that if th sensor on track 1, 2, or 3 is tripped, start the flasher until the sensor on track 4 on the far side is tripped, and if the sensor on track 4 is tripped first, activate the flashers until any one of the other 3 sensors is tripped, so it won't matter which route the train takes.

                                                  --Randy

 

 

 

The only way I can think of to configure the sensors for both crossing signals for  bi-directional on-off operation for each signal as a train passes is to configure selectable operation of crossing A and B sensors for traveling right to left and correspondingly left to right operation.

This would require an initial "west bound right to left directional sensor" to enable all of the corresponding sensors for crossing A and B and disable all of the left to right crossing signal sensors. Then install another initial "east bound left to right directional sensor" travel sensor that would power the required crossing sensors and disable all of the right to left sensors.

In essence, one set of sensors for west bound travel through both crossings and another set of sensors for east bound travel through both crossings.

On paper this would work as I had it drawn. The problem is creating low level logic circuits to power the sensors which would turn on and off the 12 vdc required for each signal flasher unit.

I understand attempting to describe my track crossing configurations in words is eqivalent to trying to describe the color green.

As you suggested and the more I think about it I'd be better served to talk to different sensor company reps and ask to upload a pictorial of my track and crossing configuration and see what they come up with. Would also serve as a shopping list for what I'd need and more important exactly where to place the sensors.

[hon30critter]

Over50

Yes, I looked at the Azatrax detection offerings - with choices of opto-sensor, current detection and IR. Same issue ... once you get beyond bi-directional single track crossing signal operation the application of sensors regardless of type becomes cumbersome and expensive.

Sorry, I guess I didn't understand how the eight channel sensor worked. I was imagining that it could handle four tracks but obviously that is not the case.

Dave

[rrinker]

  The Azatrax crossign controller isn;t set up for "anything goes" -  an 8 channel unit theoretically COULD handle 4 tracks, but the way they coded their controller is that it can have either 2 or 4 sensors per track - 2 per track is the minimum, trip when the first one is covered, as long as it stays covered, and if the second one on the other side gets covered before the first one is uncovered, stay tripped untilt he second one becomes uncovered. A single loco would have a problem - the crossing flasher would stop while the loco was in the middle of the crossing.

 If you put 2 sensors on each side, then you can do things like detect if the train stops short of the crossing and turn off the flashers, or if there is a siding on one side of the crossing, if the train gets close but then reverses direction and moved back away from the crossing. 

 The Circuitron controller seems to be extremely simple - just a basic flip clop circuit, so it has no idea which way the train is going with DCC. It has an input for track power for use with DC, where it's simple to tell the direction based on polarity. But it has no logic to say if A trips first, wait for B to clear, or if B trips first, wait for A to clear. Hence the need for a toggle to input the direction of travel when using with DCC. 

 IF the controller supports multiple sets of sensors in parallel, then there is no problem using one controller for multiple tracks, just parallel enough sensors for each track. That's why I suggest calling the vendor. IF parallel sensors work the same as if there was just one, it won;t matter which of the multiple tracks the train comes in on, and then if it goes out on a single track, no biggy. Or the other way, coming in on the one track, and it may exit via any of the 3 diverging tracks, any one of those sensors being tripped triggers the end of the flashing. But that requires the circuit to be designed to handle that, and only the vendor can answer that question.

 In a DIY situation using something like an Arduino, it's not too hard to figure out the logic needed. Just chart each possible path for the train to take through this area and figure out which sensors would be triggered for each path.

 The elephant int he room is that it's unlikely roads would ever be laid out such that one road would cross say 3 tracks and then just a few feet away another road would cross a single track. ANd in situations where this happens (it's close to nearby - on one block there's a double track main with a road across it, a block away there are 3 tracks because now there is a siding for a feed mill - there's a turnout for the siding between the blocks), the crossing protection for each street is individually triggered. A train approaching from the east triggers the east crossing lights, and about the time it gets to the crossing it triggers the west crossing flashers. Yes, that means using two controllers, with the 'start' sensor for one being placed before the 'end' sensor for the first one.

                                               --Randy

[LogicRailTech]

Over50

[SNIP!]

As you suggested and the more I think about it I'd be better served to talk to different sensor company reps and ask to upload a pictorial of my track and crossing configuration and see what they come up with. Would also serve as a shopping list for what I'd need and more important exactly where to place the sensors.

 

Hi "Over50",

 

We'd be happy to look at your track diagram and let you know how our Grade Crossing Pro might handle your situation. You can also get a sense of what's possible beyond a simple crossing by looking this document on our website: https://www.logicrailtech.com/gcp_appnote_complex_crossings.pdf