Adventures in TMCC & Legacy... Trying to master the 455Khz track signal. I've built the test car, and it is finally working..

Sorry to say guys, but the bundle of wire you all seem to be focused on should pose no problems. They carry 12VDC to the Tortoises and ground only for the 24VDC relays. There are no track wires there.

There is a 120 V power cord, but I seriously doubt that is making a difference.

I'm kind of leaning toward the idea that the upper deck casting an earth ground "shadow" on the lower deck.

I still need to run the train around, but I haven't been downstairs the last two days, as I've been helping a local train club move. They have a huge 2 rail layout that has been in place for the last 30 years, and have to be out by the end of the month. You can read about it here.

Elliot, do you use a common ground reference for all your power?  If so, those wires have the track signal on them.

No Dale, those DC systems have no connection to the track, and never will. The only DC system that will come in contact with TMCC, will be the C/MRI detection system. None of those power supplies are active yet. The DC ground will be superimposed on the track ground to activate the C/MRI inputs.

If the DC system is truly floating, it would be interesting to see how the readings on the receiver car change if you connect the DC system to first earth ground and then track common.  It might have more effect than expected.

If you have the time, I'd like to see a measurement map of the area in question.  In other words, draw the track design roughly-to-scale and jot down maybe a couple dozen readings of the signal-measurement.  Seems to me the benefit of the meter is to gain more insight rather than no, no-go on TMCC command through-put.  For example, does the meter bottom out in the middle of the bad area?  As I imagined earlier, something like those cellphone coverage maps showing number of bars might better reveal a "geographical" or electrical cabling correlation to the signal strength.

Elliot

Make sure to keep the U terminal portion of the signal going to the outside rails at least 2" to 3" away from any earth ground wires carrying the other portion of the signal, such as 110 AC lines, or any other low voltage lines which have a earth ground wire in it.  This was on of the items which Lionel's CTO group brought up in our discussions.  For regular layouts running having both portions of the signal in close vicinity should not be a problem, but for very large layouts like yours and the layout we have at the club, the overall signal looses can be significant.

Good luck,

Bob D

NJ Hi Railers 

I finally got to run the signal test train around a good chunk of the layout, and the results were pretty much what I expected:

• Lower deck high 20's to mid 30's, some engines work, most don't
• Small helix high 40's low 50's, everything runs perfectly
• Upper deck low to mid 40's, most trains run well

I just thought of something that may account for the difference between the upper and lower decks. On the upper deck, there is a single continuous ground wire feeding all the tracks. On the lower deck there are multiple ground paths, and perhaps I'm not able to keep the signal "pressure" up as a result.

The small helix has its own ground plane from bottom to top, so it's almost like cheating by creating a perfect environment. It's never had a problem.

So I guess the target value should be 45 and greater. Now the plot thickens, how to achieve that.

Elliot

Try running a second earth ground wire under the lower level the same way you have on the upper level, as one signal wire (make sure the earth ground wire is not a continuous loop).  You can try this experiment on a section of the lower level and see what happens and make sure you connect the new lower loop earth ground wire to the same source as the upper level loop.  A good place to obtain a good earth ground signal, is from pin 5 on the 9 pin D connector on the command base unit.

Also, make sure you have a good "U" terminal connection to the lower level.  The overall TMCC signal the engine sees is dependent on having a good "earth ground" and "U" terminal signal from the command base.

Bob D

NJ-Hi Railers

Thanks Bob. Not sure if you saw what I said earlier in this conversation about my earth ground. I have very easy access to it because I have a series of 120V outlets down each of the four aisles of the layout, all in metal conduit. By code, that conduit is earth ground, and tests out as such. I can tap into it anywhere very easily, and have in many locations.

While my layout is not quite as large as your club layout, I do have over 3000 feet of track. I only have one "U" terminal connection, which radiates out over a network of ground wires. I don't suspect that connection, since parts of the layout do work well.

It may be a few more weeks before I can really play with this and do some experimenting.

Elliot.  Any thing new signal wise?   Yes/no is good enough. Got to keep this thread warm.

Gregg posted:

Elliot.  Any thing new signal wise?   Yes/no is good enough. Got to keep this thread warm.

Sorry Gregg, I know it feels like forever since anything has really happened on this front. I've been busy with other projects, but I hope to get back to it this month. It still needs doing.

Elliot,

   After all this I would set up a small loop of track and test your Legacy, it maybe faulty, mine had problems NIB.  You may have a faulty Legacy.  Test it all by itself and see what happens.  

PCRR/Dave

Elliot already has one of my track signal test meters, and he has verified that both the TMCC and Legacy Bases are OK.  There is a lot of loading of the output due to the large layout, however, and we are working on that problem.

Dave, as Dale points out, we've been through that part already. Actually, the Legacy base was defective. The U post was loose, but that has been fixed.

Now the question is, why do some areas have better signal strength than others, then how do I fix them? There have been a lot of solutions proposed, I just haven't had time to try them yet. This entire project is moving up the priority list . There are some loose ends on a couple other projects that I'd like to take care of first. Then I can devote my full attention to this.

Dale Manquen posted:

Here is my version of a "squealer" for an audio output from the R2LC.  It consists of an inverter/level shifter and a 555 timer chip.  The frequency range isn't really broad, but it is enough to hear changes of RF signal strength.  I am also using my meter in voltage mode for a digital readout via wireless video.  The loudness potentiometer is 500 ohms.  The battery's positive terminal (via a switch) is connected to Pins 4/8.

I needed an acoustical baffle for the rear of the speaker, so I just decided to stick the circuit board inside the a truncated pill bottle that had already donated its closed end to another project.  It is powered off the 9V battery I am using for the R2LC.

I wanted to swap out the Harbor Freight meter for one with display illumination so that my video camera's image would be clearer, but wouldn't you know it, HF didn't have a single one in stock yesterday!  When I go to Camarillo Wednesday, I will go to the main HF headquarters to pick one up.

So now my configuration is complete - test receiver, squealer, meter, wireless video, and a 'scope and one of my Track Signal Strength meters to monitor the output of the Base.

Now what was I going to do with all of this.....?

Dale, so was this a rhetorical question?    That is, have you tried using the squealer to some effect?

I did wire up a squealer to the R2LC but to Elliot's earlier point, it is not "calibrated" in any absolute sense so you can't hear a pitch and translate it to "good"... not that there is/was any claim that it is anything more than a relative (getting warmer, getting colder) tool.  What I noticed is if the pitch changes, even a few seconds later the brain (mine anyway) has no memory of what the pitch was 10 seconds ago.  Obviously with the digital readout, one can just see it was 35 or whatever and after some fluctuation see that it is 35 again and be confident the signal strength is what it was.

So ignoring "talking" digital meters that speak the measurement, what more can be done using audio or any other indication method to provide a better tool for troubleshooting?  In an off-thread message Elliot suggested perhaps a limited number of pitches might be easier to interpret ... similar to red-yellow-green.

.. what more can be done using audio or any other indication method to provide a better tool for troubleshooting?  In an off-thread message Elliot suggested perhaps a limited number of pitches might be easier to interpret ... similar to red-yellow-green.

 

 

I think I lost part of this thread, so excuse me if I miss the point, but how about something like this, maybe using king-size LEDS, visible from a distance. Or, is an audio reporting method a pre-requisite at this point?

http://www.ebay.com/itm/like/2...ps&ul_noapp=true

Basically an LM3915 module.

PLCProf posted:

.. what more can be done using audio or any other indication method to provide a better tool for troubleshooting?  In an off-thread message Elliot suggested perhaps a limited number of pitches might be easier to interpret ... similar to red-yellow-green.

 

 

I think I lost part of this thread, so excuse me if I miss the point, but how about something like this, maybe using king-size LEDS, visible from a distance. Or, is an audio reporting method a pre-requisite at this point?

http://www.ebay.com/itm/like/2...ps&ul_noapp=true

Basically an LM3915 module.

As I see it, this is a work-in-progress.  Audio feedback is/was raising the flag up the flagpole to see who salutes.   It appears some guys have hooked up a video camera so the measurements can be viewed/recorded/documented from a distance.

I recall GRJ also proposed the LED bar-graph method but I'm not aware of anyone who has actually done so to work out any kinks.  For example, in LM3915 applications I'm familiar with the chip is measuring audio levels and hence the LED steps are calibrated in dB-steps which of course is non-linear.  OTOH, the R2LC meter pin puts out a signal that is already "linear-in-dB" so the additional dB conversion might make for a difficult-to-interpret display!  Also, I notice on some of those attractively-priced eBay LM3915 modules the input connector is labeled "AUDIO" which makes me wonder if it is expecting an AC signal whereas the R2LC meter output is a DC signal.  In other words, i's to dot and t's to cross.

OTOH the simple resistor+capacitor with a freebie Harbor Freight meter may be sufficient...and can be added to horseshoes and hand-grenades where close counts. 

OK, I will throw another thought out. I agree that that concept of pitch generated from Dale's squealer may be difficult for non-musically trained ears to evaluate, but how about lowering the frequency to generate clicks in the fashion of  a geiger counter? A good signal might be scaled to be a more or less continuous buzz, 20 Hz or so, a weaker signal would decrease from there causing the individual clicks to become audible. 

It works in all the sci-fi movies.........

stan2004 posted:

, I notice on some of those attractively-priced eBay LM3915 modules the input connector is labeled "AUDIO" which makes me wonder if it is expecting an AC signal whereas the R2LC meter output is a DC signal.  In other words, i's to dot and t's to cross.

OTOH the simple resistor+capacitor with a freebie Harbor Freight meter may be sufficient...and can be added to horseshoes and hand-grenades where close counts. 

 

 

 

The data sheet for the LM3915 shows a DC coupled circuit. Looks like a good choice for a display maybe with some input range adjustment. Try one for $2 and answer most of these questions.

Measurement of the signal strength around the layout must be combined with information on the sensitivities of various locomotives.  Maybe we could find a "weak" spot and then place one of the less sensitive locomotives there to gauge just how much signal is needed for proper operation.  The measured numbers will vary depending upon the R2LC and the construction of the test car and antenna, but the bottom line is "what does it take to make the worst engine run properly?"

Dale, without going through all 30+ engines on the layout, I have arrived at what I think is a pretty fair generalization based on observed signal strength and engine behavior. Below 32 or so is flat out bad. Readings of 33 to 45 are marginal, and 46 and up is good. Of course, the stronger the better.

I'm leaning toward antenna design, placement and orientation as the key to solving this problem. I want to play with those variables on the test car to see if this theory holds water. As I mentioned earlier in this discussion, I have some early TMCC engines that don't suffer from these signal issues, and I noticed that their antennae are of a vertical, nose mounted design, very different from the horizontal top mounts commonly found in newer diesels.

Elliott,

I just read this entire thread over the past three days. I felt as though I were back at the Purdue Electronics Lab troubleshooting our experiments! It has been quite a refresher for me. I want to thank you, Dale, John, Stan, Bob, Chuck, et al for your contributions.

Among the items I discovered is the "TMCC Signals Basic", by Dale M., dated August 2, 2011. I had learned about this from a different source, but Dale explains it very clearly in his document so anyone should be able to easily understand it, I believe.

Based on some of the discussions posted, I consider myself rather lucky in that save for one instance, which I readily solved with an added earth ground wire, I have had zero problems with Legacy. I run both DCS and Legacy without issues. Though not as large a layout as yours (Elliott), mine is no too small - the train room is 33 x 38-ft and most of it is occupied by the layout, on three different levels; or four if you count the smaller subway loop. I have over 900 feet of track, 58 turnouts, and about 26,000 feet of wire, and I am not done yet with the wiring.

Why so much wire? Because a run from the control panel to the 'other side' takes 120 feet of wire going around the edge of the room. The average run of wire is 80 feet, and given the number of power feeds, sensors, turnout controls and signals, and relay control, the wire added up very fast. I have run the last few drops to the 'other side' over the ceiling, and this saved about 60 feet of wire per run. I also have about 20 wall warts of various voltages, connected to remote-control outlets, scattered throughout the layout for lighting and for accessories.

Given all the wire running under the layout I guess I am lucky in not having any signal problems with Legacy?

 Thank you all!

Alex (Alexander Müller)

Big_Boy_4005 posted:

Dale, without going through all 30+ engines on the layout, I have arrived at what I think is a pretty fair generalization based on observed signal strength and engine behavior. Below 32 or so is flat out bad. Readings of 33 to 45 are marginal, and 46 and up is good. Of course, the stronger the better.

I'm leaning toward antenna design, placement and orientation as the key to solving this problem. I want to play with those variables on the test car to see if this theory holds water. As I mentioned earlier in this discussion, I have some early TMCC engines that don't suffer from these signal issues, and I noticed that their antennae are of a vertical, nose mounted design, very different from the horizontal top mounts commonly found in newer diesels.

Elliot

Have you tried to run a new earth ground wire under a portion of lower level, the same way you have it run on the upper level, as one signal wire (make sure the earth ground wire is not a closed loop).  Also disconnect the existing earth ground wire you have on the lower level.  There could be a problem on the way the lower earth ground wire is run/connected causing your problems.  We ran across similar issues at the club and now every time we modify the earth ground wiring, the earth ground signal test car and scope is attached to the layout to check reading before and after we make changes.  Checking a portion of the lower earth ground wire system may be easier than opening engines to check/update antennas.

If you do get into the mode of updating engine antennas, I found using 3M 1/2" or 3/4" copper tape as an antenna replacement provided better signal strength readings than the same length of copper wire.  You can do your own experimenting with different antenna type with the earth ground signal car you built.  Just add different types of antennas to the existing antenna in the signal car and read the new signal strength on the meter.  If anyone uses copper tape in their engines, make sure that you don't rely on the adhesive on the tape to hold the it to the plastic body, use a thin  coating of silicone adhesive on top of the copper tape to insure it does not peal off the shell and short out engine boards.

Good luck,

Bob D

NJ hi Railers

We know we can only have one command base, however is there any advantage or disadvantage of running more than one wire from the "U" connection to different locations on the layout.   ??

Gregg posted:

We know we can only have one command base, however is there any advantage or disadvantage of running more than one wire from the "U" connection to different locations on the layout.   ??

Gregg, in my case the TMCC and Legacy bases are located in the center of the room. There are two power supply panels. The track ground wires radiate out from there. There is a connecting wire between them, and the Legacy output is connected to that. So, even though there is only one wire connected to the base itself, there are still multiple paths down stream.

Bob, thank you for sharing all of your knowledge and experience here. I have read all your posts as we've gone along. When I'm actually ready to do some real work on this project, I will go back and reread everything. If you think of anything else, by all means, say so.