Interlocking signalling for newbies

[jfrey40535]

Hello everyone, this is my first post to the forum.

I am looking for some guidance on how to approach the installation of signals at an interlocking that is comprised of 4 switches.
I am only looking to install controls for the signals and not run it through my DCC system (Digitrax).

The interlocking is 2 tracks, bi-directional operation. The signals being installed are LED. The signals themselves are a custom built G-type, 2 target on a mast, which will cover the 2 tracks. So 4 targets total, 2 for each track.

If I understand correctly, I will need sensors on each of the 4 switches to detect switch position, then sensors on both sides of the interlocking to detect occupancy. I plan on using IR sensors if I go with Azatrax MRD1-NV for detectors. Then I would need a series of sensors on both sides of the interlocking to detect occupancy status for 2 blocks on either side of the interlocking. From there the detectors would connect to a controller which would interface with a computer to run the logic.

I would like the signals to have the ability to display a number of aspects depending on block and switch status, outside of the basic stop, clear and approach.

A friend recommended I consider C/MRI, which seems extremely complicated though probably the best out there in terms of flexible programming. There are several other options and I'm looking for some feedback from those who've been down this path on what works best. I have a little experience with JMRI for programming decoders, but that's it.

If anyone can make a recommendation, please let me know what you've used for detectors, controllers and software. Any guidance would be appreciated!

 

[D&J RailRoad]

I'm using the Train Controller Silver software along with the Digitrax BDL168 block detector and SE8C signal and turnout control boards.
In the video you can see the signals change as trains go from block to block or the turnout is thrown.

 

[dave1905]

There are two types of signals, route and speed, so whichever one you choose will determine the actual indications you use. In reality the lights will pretty much be the same.

Whether the top or bottom head displays a favorable indication is determined by the position of the switches and the color of the favorable indication is determined by block occupancy.

In real general terms, if both switches are lined normal, the top signal will be favorable. If a crossover route is lined for the move, the bottom signal will be favorable. If a crossover is lined against the move, it will be all red.

If there is one clear block beyond the interlocking on the route, the favorable signal will be yellow. If there are two clear blocks beyond the interlocking, the signal will be green. If the block next to the interlocking is occupied the signals will be all red.

 

[jfrey40535]

Thanks Ken and Dave.
I am modeling the Reading Railroad, so my signals will indicate speed. I have a fair understanding of how blocks and interlockings work, I'm more or less trying to wrap my head around the hardware and programming required.

I am using JMRI to program my locomotive decoders, so I've decided I will stay with that for the programming. For the moment, I don't plan on tying the signals in to the DCC system itself, I already have the Digitrax PR4 for programming engines, so I'm considering using the Digitrax SE8C for the decoder.

Based on the research I did, my system would consist of:
Azatrax MRD8 with IR sensors for occupancy detection (For one signal mast I will have 3 sensors) -which should cover 1 signal with 3 sensors each plus 2 switches on a single track - That's 6 terminals used, leaving 2 for the Tortoise switch machines.

I would then use the Azatrax GS-CA to tell the SE8C what position the switch is in by connecting it to the MRD8

Digitrax SE8C for decoding the sensors and switches

And wiring would be as follows:

Once all that is connected, I connect the SE8C to the Digitrax PR4, and connect the PR4 to a computer terminal and use JMRI to detect the signals and sensors and begin programming.

Does that sound correct?

 

[D&J RailRoad]

I'm not to sure about your switch machine connections. Typically the two outboard contacts on the Tortoise machine are for the power input to drive the Tortoise machine motor. To make the Tortoise go the other way, the power is reversed. Now, if your switch controller does that and the two wires going to the M1 and M2 contacts are to sense turnout position, you are good to go. If the M1 and M2 are actually the SE8C board, you are duplicating the SE8C board capability. The SE8C board provides the power for the Tortoise and senses the turnout position. This is integrated into the loconet connection that you would apply to the PR4. The SE8C turnout control can be toggled by a momentary push button or by your switch control on your Digitrax throttle.

 

[dave1905]

Small world, I model the W&N Branch, but in 1900-1905.

 

[trailrider]

You might want to discuss this with (IIRC...been awhile since I spoke with him) at Azatrax. He has been most helpful with my crossing detection system. As far as interlocking is concerned, I am not true to prototype, but simply use signals to tell me the alignment of turnouts and polarity across return loop and crossovers. I use 12-16v incandescent bulbs, but with the proper resistors, LED's would work as well. If the polarity is correct, the green aspect or green over yellow will light. The bulb leads are soldered directly to the rails. For correct polarity across an insulated block, I connect one lead to the N rail and the other to the S rail on the other side of the insulators. If the polarity is wrong, one lead from the red bulb is soldered to the N rail on one side of the insulated rail joiner, and the other lead to the N rail on the other side of the insulator. If the red light shows, I flip the DPDT toggle on my control panel. For turnout alignment, things get a little more complicated, but common goes to the frog, and the other leads to the stock rails. Where I have Atlas switch machines, I add a Snap Relay. Probably NOT what you want, but it might help someone else.