Reading DCC data using a propeller on track. (digital model railway control)

Clock LoopClock Loop Posts: 1,577
edited 2018-01-11 - 06:43:17 in Propeller 1

My old setup before setting up the 8 zone test track.

This thread is dedicated to my investigations on dcc railroad transponding, with a goal to use the propeller to diagnose dcc track problems and data, and cast that data to a parallax WX for viewing on any telnet ansi terminal running capable device. (all mobiles have term apps)

This will get its power from the track but NOT send data to it, just get data from it, at least not at first, that would be nice, but will take time to figure out.
I know a few others have done this, but they haven't really included all the juicy photos, video, schematics, programs, and discussion that is really needed for a topic like DCC.
So I am tackling that with propscope screen shots and video, plus desktop capture of jmri plus more.

I am using a setup that will enable you to follow along pretty well as its developed.

Currently I am using a propscope to get the data I need, and it has served me well, with emphasis, that I haven't even touched a current sensor yet, but will be. (to display the transponder data, better)

I don't know alot about dcc. But thats changing fast.

I can see the transponding on the propscope when triggering from the transponder led in the locomotive.
If I change this led to a weaker resistor, and one that is allowing much more current, I can then see that on the rails, as a slight dip.
That also affects the transponder receiver, it increases the "volume" of the transponder by pulling more current.

I am having problems with a specific transponder model causing havok on the transponder receiver. (i think its the transponder model, because another model doesn't do this)
The transponder that is causing the problem, causes the same problem for the working transponders, so i suspect its in the transponder receiver that the problem can be found.
IF I look at the transponder receiver current sense, with my own sensitive current sense device, this will tell me what data is REALLY going down the pipe.

But all this is so hard to get going and do and figure out the tools and parts (current sensor) etc i need.. so.. i figure why not make something that can go on the rail and assist in my investigation.

To get started on CONTENT, I have a few videos showing jmri running trains and it also shows the transponder messages coming from the transponder receiver that are constantly swapping.

This video shows a jmri screen shot of a train going around doing transponding.

The next two show the transponder reporting two trains going around the track, but their transponders are randomly getting confused.

And this video is a miracle, it actually transponded two trains at the same time properly, until 1 point where it reported it wrong once, and then corrected.
I reconnected some layout wires and that happened. It turns out it was a fluke. Because as soon as I restarted the layout, it was back.

So I disconnected the layout and wired up a test station.

Back to the transponder resistor, I found that different decoders have different transponder output levels on the same track, so this presents the pull on the transponder receiver differently, and that, might be where my problem will show.

I have tried different resistors, and they do make a difference. My transponder receiver is new, so its very possible that its simply a firmware bug.
I am using it as an excuse to understand the dcc system, and then, the equipment that I have already purchased.
I would like to repair it and not leave it in others hands, or trash, since stuff dies all the time with 'lectrics....

To do that, I need to start understanding it, so follow along if you wish.
I suggest you get a dcc system and a prop scope and follow along!

The next video/images here will show a capture of the transponder on the rails and on the transponder wire(thats the trigger)
I still haven't figured out what the data is and all that, to determine what is in fact going over the rails.

For now how about a video of a 3D railroad game I own. Rendered on a overkill system. (system specs are in the youtube comments)

1. Silicon gel filled square. <---2.Sonics(ultra even). 3.Lazers. 4. ?
54 propeller chips were connected to One, to rule them all....


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