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Model Railroading > Driving Atlas Signal with Digitrax system

Date: 03/25/23 21:50
Driving Atlas Signal with Digitrax system
Author: atsf121

I'm getting serious about signals on my layout, finally, and have been looking at the Atlas Type G signals for my SP portion of the layout, along with the old BLMA, now Atlas Cantilever Bridge.  I'm having trouble finding any information online about connecting the Atlas signals to the Digitrax system.  I plan on using the Digitrax BDL168 and/or BD4Ns for detection, along with the Digitrax SE74 to drive the signals.  What I'm struggling with is the connection between the Digitrax platform and the Atlas signals.  Any suggestions on videos or web pages that explain how to pull that off.  The things I've found so far show that Atlas has an unusual plug setup but it looks like that's to hook in to their propritary signal driver.  Do I have to connect the Digitrax Loconet to the Atlas Signal Control Board or Interlock Control Module?

Thanks, trying to budget time and materials and do this right the first time.


Date: 03/26/23 00:04
Re: Driving Atlas Signal with Digitrax system
Author: santafesteve

Ditch the Digitrax and the Atlas system. To compliated of system. Check out SIGNALOGIC SYSTEMS. Check out Kevin Rudco first.

Date: 03/26/23 06:53
Re: Driving Atlas Signal with Digitrax system
Author: andrewcastle

The world of model railroad signalling can definitely make you scratch your head. I will see if I can help a bit. For context my layout uses the Digitrax system with BDL168s for detection, SE8C for signal driving, signals made from Showcase Miniature kits, and CATS/JMRI for logic. If any of my information below is wrong I welcome corrections.

First you need to break a signal system down into detection, signal driving, and logic. The Digitrax system provides BDL168s for detection and SE74 (SE8C replacement) for signal driving but relies on a computer running third party software for the signal logic. The Atlas system has the signal control board which contains the logic and drives the signals but relies on third party hardware for detection. The Atlas system can do ABS (automatic) signalling, the Digitrax system can do ABS or CTC (dispatcher controlled) signalling depending how the software is set up.

The Atlas system seems to be designed for a detector with a single output such as the NCE BD20 or Iowa Scaled Engineering ATOM. These have a current output on a single wire when a block is occupied. The Digitrax DBL168 can do 16 blocks but is designed to broadcast occupancy information over Loconet. The Atlas system does not connect to Loconet so that is a problem. The BDL168 does have connectors to hook up an LED for each block to indicate occupancy. You may be able to use these outputs to connect the Atlas signal control circuit board but I have not been able to find any info on that.

If you want to use the Digitrax BDL168 and SE74 then you can drive the Atlas signals with none of the Atlas circuitry. You would cut the plug off the wires on the Atlas signals and connect them to a Digitrax TSMK terminal strip. These strips have built in resistors to drive LED signals. You then connect the TSMKs to the SE74 using the SDCK signal cable kit. The BDL168 and SE74 both connect to Loconet, your computer would connect to Loconet via a Locobuffer USB or the USB port on a DCS240.

For software to run the Digitrax system the most common would be JMRI or a combination of JMRI and CATS. These are free. There is another company that sells similar software but I can't remember the name right now. To set up JMRI you build a table for the detection sensors, a table for turnouts, and a table for signals. You can then build a panel and set up the signal logic and if you want build an older style CTC panel. CATS makes a modern computer-based display CTC system, it uses the detection, turnout, and signal tables from JMRI but builds its own CTC panel and signal logic.

Digitrax has alot of information on their website but it's not easy reading. The Atlas website has very little information but I was able to find 

YouTube has some good tutorials on JMRI and CATS, your ability to find quality information on the Atlas and Digitrax systems may vary.

Andrew C

Date: 03/26/23 11:26
Re: Driving Atlas Signal with Digitrax system
Author: sfn2633

This is all very good information.  However, signaling is a hobby within a hobby.  Is atsf121 wanting CTC and computer interface control?  Or could it be CTC with switch/relay relay CTC panel.  If he wants an ABS system, the current Atlas product includes what you need right out of the box I believe.  Also the signals are very nice and can work with any system.

This website http://www.lundsten.dk/us_signaling/  gives a good overview of various track authorities and the signaling that goes with it.  Bottom line is how is the layout planned to operate and go from there.

Jeff N


Date: 03/27/23 06:29
Re: Driving Atlas Signal with Digitrax system
Author: atsf121

Thanks Steve, Andrew, and Jeff for the quick replies, this is what I love about Trainorders.  I've looked at Signalogic Systems, and was seriously considering Layout Command Control after sitting through a presentation at the Salt Lake NMRA convention a few years ago.  But since I already have an investment in Digitrax, and LocoNet is kinda LCC anyway, I'm going to stick with them for this layout.  I do hope LCC takes off because my computer programming side really likes the concept.  I was able to snag some of the Atlas signals I want on sale from TrainLife last night, will pick those up this week.  Clipping the plugs in order to wire things up makes to the Digitrax system makes sense, figured that was the option, but was hoping there was an 'easier' way.  Guess I'll have to break out my old tackle box full of eletronic breadboards and resistors from when I was an elecitrcal engineering major in college - before I switched to computer science.  Kept those for my model trains, used them to build operating crossing lights on my college layout.  And now I'll get to use them again, if I remember how!

As to some of the question that were brought up, a couple of answers for folks who are interested.  I'm building a multiple layer (not level) layout to represent the SP & ATSF lines along San Pablo Bay east of San Francisco, CA.  The SP line on the first layer models the Cal-P and will be 2 Main Track CTC and I will control that via JMRI/CATS with the computer to LocoNet connection.  This is where the Atlas Type G signals are going to be used.  The ATSF layer models the Stockton Sub and will have ABS signals and will be distapached via Traffic Warrent Control (TWC), that one will be a little easier to implement.


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