2 rail TMCC & DCC Just Curious

Could a Lionel Railsounds sound card , the one of the 3 boards used in the tmcc system be somehow wired in to be used with a DCC non sound decoder like a Digitrax DG583S ? Just Curious, thanks

Please clear this up for me?  2 rail is not really a problem versus 3 rail as long as the wheels are isolated.  Soooo...any 2 Rail engine would not have any problem running with anyone's internals as long as AC power was used. 

IS there an assumption that all 2R is DC power?  Because that would not work with TMCC. 

TMCC would not function on a DC 2 Rail DCC layout.   MTH PS-3 would and infact has a built in DCC decoder.  G

"Please clear this up for me?"

Prior to the 1980's, 2-rail O-scale (and HO and N) locomotives were powered by straight DC.  They had no electronics.  Track power was thus DC.  With the advent of command control systems (which eventually became DCC), track power changed to AC with a square waveform to carry the DCC signal.  Our 3-rail TMCC locomotives do not like the AC waveform on DCC layouts.  DCC locomotives won't run on a layout with sine wave AC like Lionel transformers put out.

Scratchbuilder1-48 posted:

Could a Lionel Railsounds sound card , the one of the 3 boards used in the tmcc system be somehow wired in to be used with a DCC non sound decoder like a Digitrax DG583S ? Just Curious, thanks

To answer your question: Yes. I had this conversation with Jon Z, former owner of The Electric Railroad Company and who now works for Lionel, where I asked him if it was possible to make a DCC decoder that will interface with a Lionel Railsounds board. Basically it would be just like you are describing: a non-sound decoder that will have sound once you mount the Lionel Railsounds board to it. Jon told me, Yes it is possible. He even sent me a schematic of the circuit  which I have somewhere but this was so long ago (probably about 10 years now) that I don't even know where it could be. I'm not an electronic engineer so I never did try to build the circuit. I was hoping someone would have come out with such a decoder. I have several Lionel Railsounds locomotives that I would like to run under DCC and still have the Lionel Railsounds play but the decoder never got produced. I guess there just wasn't enough interest. Lionel recently has come out with a board/decoder that will run under DCC and has Railsounds but these are only used in S scale and as far as I know are not available for separate sale. I'm sure they would work in any O scale locomotive that has only one motor like an Atlas SW. A little beefing up and I have no doubt they would work in any O scale locomotive.

marker posted:

In the early 2000's maybe back in the late 90's, Atlas sold 2 rail diesels with TMCC.  Back then there were some people dabbling with TMCC in 2 rail but that faded as the preferred control system was DCC.

 

I'm curious if it was possible to run both systems concurrently.  I don't think it was but I'd like to know.  I'm moving to DCC on my 2 rail layout but have TMCC equipment and some early Atlas diesels.  It would be handy if I didn't have to replace the electronics in the Atlas diesels right away.  The move to 2 rail is tying up the funds for DCC boards.

You can run both systems on the same layout, but not at the same time. A DPDT switch connected to the main track buss would let you switch between the DCC source and the AC/TMCC/DCS source. I've been planning to implement this when I build a layout as I've been scoping out some possible 2-rail DCC acquisitions, plus I plan to put DCC in the 2-rail switcher I currently have.

Scratchbuilder1-48 posted:

Could a Lionel Railsounds sound card , the one of the 3 boards used in the tmcc system be somehow wired in to be used with a DCC non sound decoder like a Digitrax DG583S ? Just Curious, thanks

Yes it can. The decoder has to have F1 and F2 outputs for whistle and bell. Heres the hard part; now you need a chip like from the TAS UCUB that takes logic levels and converts it to serial data. Then you apply the serial data to the railsounds boards. So you really end up making a little interface board to support the PIC chip.  Somehow that seems like a lot of work.  I'd probably just spend my money on a Phoenix sound board. 

Regards,

Lou N

2 rail tmcc is AC power only. DO NOT put any tmcc on DC power track, unless you want to toast some marsh mellows while all of your tmcc electronic boards are burning up. If you want smoke and all of the bells & whistles in steam engines for 2 rail go with DCS. Here is a video of my brass weaver pocono that was upgraded with DCS 2.0.

I can run this engine from AC or DC power, I had the 2.0 board replaced with a 3.0 board. So I can control it from DCC, DCS or straight from a transformer.  

I can't see how applying DC power to a modern locomotive would roast any marshmallows.  the very first thing that happens inside any TMCC engine is that the AC power is converted to DC with a bridge rectifier.  Thus if correctly polarized DC was applied, it would flow through the rectifier and output proper DC, on the other hand if reversed polarity DC was applied, it would be stopped by the rectifier and the command boards would see 0 volts.  

I do not know the effect of applying the positive side of a DC source to the U post on a TMCC base.  This MAY smoke the base, but I simply do not know.  

Second thing to clear up is the myth that the track is used as an antenna to broadcast the TMCC signal.  While TMCC engines will pick up the U post half of the TMCC signal through the air using their frame as an antenna, as the system is designed, the radio receiver receives this half of the signal through direct contact with the rails.  The broadcast side of the signal that the engine's antenna actually picks up is sent through your houses electrical wiring, through the third prong, earth ground part of the outlet.  The house's wiring then acts as an antenna to broadcast the radio signal, and the engine's antenna picks this up.  

When it comes to DCC, the power to the track is technically AC, but not in the way folks normally think of it.  Rather than a smooth sine wave DCC sends a square wave that varies in duration for each cycle based on the data being sent.  Similar to morse code, a short cycle represents a 1, and a long pulse a 0 in binary data.  This happens very, very fast.  From the information I can find, the DCC signal is somewhere in the range of 100KHz.  This high frequency power source is likely not very good for carrying the 455KHz TMCC signal which is intended to operate on a 60Hz, smooth sine wave carrier.  

It would be worth giving a try to running a TMCC engine on a track 'powered by' DCC, on a track only a few inches away from one 'powered by' TMCC.  I think the frame of the loco may be able to pick up enough of the TMCC signal from the parallel track to function correctly.  If this does work, one could run a solid wire beside the track on their layout  connected to the U post of the TMCC base, to broadcast this half of the signal, rather than supplying it from the track.  I would expect the signal to be weak, but it just might work.  

JGL.

Information sources:  

DCC Wiki entry: https://en.wikipedia.org/wiki/Digital_Command_Control

TMCC Signal Basics by Dale Manquen: http://www.trainfacts.com/trainfacts/?p=317

No.  TMCC runs on an AC carrier wave and DCC runs as a square wave on a DC carrier.  While TMCC is a version of DCC, the underlying electrical systems are not.

JohnGaltLine posted:

I can't see how applying DC power to a modern locomotive would roast any marshmallows.  the very first thing that happens inside any TMCC engine is that the AC power is converted to DC with a bridge rectifier.  Thus if correctly polarized DC was applied, it would flow through the rectifier and output proper DC, on the other hand if reversed polarity DC was applied, it would be stopped by the rectifier and the command boards would see 0 volts.  

I do not know the effect of applying the positive side of a DC source to the U post on a TMCC base.  This MAY smoke the base, but I simply do not know.  

Second thing to clear up is the myth that the track is used as an antenna to broadcast the TMCC signal.  While TMCC engines will pick up the U post half of the TMCC signal through the air using their frame as an antenna, as the system is designed, the radio receiver receives this half of the signal through direct contact with the rails.  The broadcast side of the signal that the engine's antenna actually picks up is sent through your houses electrical wiring, through the third prong, earth ground part of the outlet.  The house's wiring then acts as an antenna to broadcast the radio signal, and the engine's antenna picks this up.  

When it comes to DCC, the power to the track is technically AC, but not in the way folks normally think of it.  Rather than a smooth sine wave DCC sends a square wave that varies in duration for each cycle based on the data being sent.  Similar to morse code, a short cycle represents a 1, and a long pulse a 0 in binary data.  This happens very, very fast.  From the information I can find, the DCC signal is somewhere in the range of 100KHz.  This high frequency power source is likely not very good for carrying the 455KHz TMCC signal which is intended to operate on a 60Hz, smooth sine wave carrier.  

It would be worth giving a try to running a TMCC engine on a track 'powered by' DCC, on a track only a few inches away from one 'powered by' TMCC.  I think the frame of the loco may be able to pick up enough of the TMCC signal from the parallel track to function correctly.  If this does work, one could run a solid wire beside the track on their layout  connected to the U post of the TMCC base, to broadcast this half of the signal, rather than supplying it from the track.  I would expect the signal to be weak, but it just might work.  

JGL.

Information sources:  

DCC Wiki entry: https://en.wikipedia.org/wiki/Digital_Command_Control

TMCC Signal Basics by Dale Manquen: http://www.trainfacts.com/trainfacts/?p=317

Are you sure about this?  Please identify the full bridge rectifier on any of the following components: Mother board, R2LC, RS, Power Supply board.   G

TMCC uses the zero cross of the 60Hz track power for data synchronization.  End of story; no DC, no DCC.  DCC is ~8kHz.

Regards,

Lou N

GGG, I'd assume as a repair tech you have access to schematics that I do not.  I suppose it is possible such boards use a single diode to convert AC to DC.  in either case the net result is the same, there is no path for electrons to take in reversed polarity, thus nothing that could be damaged.  The only board schematics I could locate were on the TMCC manual thread and none of the boards mentioned were there.  The most recent post shows the ERR sound converter which uses a single diode before a voltage regulator.  

Anyway, I am very curious for technical information on any board in use, as well as technical information showing how DC current could damage any of these boards. 

JGL

JGL, I was being a little tongue in cheek.  If you don't know why make  the statement.  Early board (LCRU) were in fact single diode to  regulator.  See Lou's comments above.  Beyond that, some times input are also directly fed as a signal to other components.

Bottom Line is they don't work.  Which went back to the first post I made about 2 Rail versus 3.  How many rails really is not significant.

The type of power used and the electronics matter.  Plenty of 2 rail AC layouts and 3 Rail DC layouts.  You could  do either with an MTH PS-2 or 3 2R/3R engine.   G

GGG, the comments on rectification of the power were directed at this comment by DL&W Pete: "DO NOT put any tmcc on DC power track, unless you want to toast some marsh mellows while all of your tmcc electronic boards are burning up."

Use of a bridge made sense to me, as I've seen folks report that TMCC engines will run on as little as 8VAC track power.  Through only half wave rectification 8VAC will only produce about 5.65 VDC.  that is more than a full volt below the 6.7 volts required in the input side of a 5 volt linear regulator, thus I made the assumption that a full wave rectifier was needed.  It now seems that is not the case.  

I would still like a technical explanation on how DC current could damage devices that are rectified in any manner.  I can't rule it out as possible, but it does not make sense to me.  

As for the AC requirement for TMCC, I agree that it is needed for the signal carrier.  As my earlier post suggested, however, I am not certain that the AC component carrying the TMCC track signal must be connected to the track that is powering the locomotive. In other recent threads several folks mentioned that TMCC engines will receive a signal without trouble on tracks that are not connected to the TMCC base.  In one such case a poster stated that their bench top test track was some distance away from the layout and had no connection to the base's U post, but that it worked just fine.  Thus my thought of running a wire along side the track with connection to a standard transformer and the TMCC U post output.  In theory this would broadcast the track signal side of the TMCC signal to the engine's frame/shell.  

The larger problem here seems to me that a TMCC engine may effectively short the output on the DCC signal.  I'm unsure on this, as the capacitor used in rectifying current in the engine would be after the diode(s), so it would be isolated from the track.  Really just don't know.  

JGL

This is a very interesting thread!  

Does anyone think it would be possible to create a device that would reside in a locomotive and take TMCC commands and output DCC to a decoder to control the motors and provide sound?

I like the sound fidelity of my HO locomotives and would like to provide the same for my TMCC O gauge locomotives.

GNERR posted:

This is a very interesting thread!  

Does anyone think it would be possible to create a device that would reside in a locomotive and take TMCC commands and output DCC to a decoder to control the motors and provide sound?

I like the sound fidelity of my HO locomotives and would like to provide the same for my TMCC O gauge locomotives.

Is it possible?  Sure.  I don't even think it would be particularly difficult to accomplish.  

I think you would probably be better off leaving the motor control as it is, and only worry about the sound end, but then I'm not familiar with what features DCC offers for motor control that TMCC does not.  

I do not know how sound quality compares between them, but I suspect you may get satisfactory sound out of current generation RailSounds boards without having to use a board between to convert to DCC.  

If you already have a DCC equipped locomotive, I think it would be fairly straight forward to install a board that would receive TMCC signals and output the corresponding DCC signals, for whatever commands are the same.  Access to any command that doesn't exist in TMCC, however would be more difficult.  The same could also be done the other way around, to make a TMCC engine run on a DCC layout.  

In either case a small micro-controller could easily accomplish the task of "translating" commands from one system to another incompatible system.  The process would be fairly similar to what I did here for TMCC control of LionChief engines.  Note that while I'm using a fairly large board and using the base's serial port, the same thing can be accomplished with a board the size of 2 postage stamps, and receiving serial data from a R2LC radio board.  

JGL