Measuring the TMCC/Legacy track signal strength

Dale, an expansion of this product idea would be a traveling signal strength car that uses the R2LC to measure the signal strength around the layout.  I know this has been discussed before, but it would be a great tool, especially for folks with larger layouts that are experiencing issues.

Yes, I have a breadboard of such a car, and it isn't an easy task.

Yep, that's why it's a good product, not many folks will tackle it!

Dale,

If you decide to do a car put the NJ Hi-Railers down for the 1st one off the line!!  I'm hoping your meter rig will show up tomorrow.

Thanks for all your work and knowledge with this.

In re the traveling signal strength car, "Gary E" apparently had success tacking a wire to the meter output of the R2LC receiver chip, adding a resistor and capacitor, and a DC voltmeter.  Not saying it's easy but less than a $1 in parts if you already have a meter and an R2LC.

https://ogrforum.com/t...ly=21984675511801945

Well, the trick is getting the information back to the tester, it's difficult to follow the locomotive into tunnels and the like with a meter!

Even for the basic traveling voltmeter boxcar that just measures track voltage with an included meter, I've always thought it would be handy to have a little speaker that generates a tone proportional to the reading.  It might take some getting used to, but then you could "listen" to the voltage or, in this case, the 455 kHz signal strength.  A 555 timer chip configured as a voltage-controlled oscillator driving a small speaker shouldn't add more than $1-2 in parts.  I'm not saying it's easy to do...

Audio isn't a bad idea, but if you're trying to do this with other things running, it could get lost in the noise.

The VCO is an interesting idea, but I think that moving the measurement car by hand isn't too much of a burden if the car is primarily for troubleshooting troublesome areas.

For a tunnel you could extend the meter leads, but that might also change the signal pickup.

I'm thinking of folks like the NJ Hi-Railers, they have tunnels that are a trifle long to move the car by hand easily.   Of course, they're the kind of folks that would want to have such a car.

 A pulsed audio signal, a tone, with a rate proportional to signal strength wouldn't get lost in the noise.

John,

We spend so much time under the layout a little more with a signal strength car would be most welcome.  The idea of baselining a section, installing a ground wire  and then measuring the resultant signal would have unbelievable value.  

You know what would be a good idea, is a receiver to measure track signal as you go around the layout.  OH some one already mentioned that, and some one already experimented with one.

When I mentioned it, I thought of you.  I had seen Gary's experiments, so it seems clear such a car would be possible.  As long as you don't mind climbing under with it, the meters would probably be the ideal solution, you'd have real measurements that you could compare.

I know the R/C aircraft industry has relatively inexpensive and simple electronics for reporting back to the transmitter various information from the on-board aircraft receiver. I'm guessing someone knowledgeable (rules me out ) could jury rig one of these to report signal strength back from anywhere on the layout that has RF signal reception.  Any thoughts?

Interesting you say that, because in the research I did years ago, some of these smaller RC helos used the same radio as the Lionel R2LC.   G

My brother is big on the video flying, and he has a couple of quads and a standard plane with a camera and instrumentation that is broadcast back to the video goggles he wears to fly them.  They even have GPS and autopilots, it's pretty tricky.

I don't know about inexpensive, the typical outfit gets knocking on the door to $1000 for both ends!

What about the car having a way to measure distance and the readings taken are recorded as the is travelling the loop. Then it could be downloaded from memory to a USB Thumb Drive and transferred to the computer to analyze. You could then attack the different areas that need attention by manually going to those areas.

Just a thought! I know there are holes in the idea but we need to keep thinking.

Or a video camera also, to visually see the areas that are weak and by syncing the video to the track recordings you will know where to attack!

Someone good with Arduinos could make one that reports back to your computer the signal with a video feed and signal strength via WiFi or Bluetooth.

Good idea with the Arduino, there are many WiFi and BlueTooth options available, and they're cheap to boot.  You could use one of the A/D inputs to digitize the signal strength and broadcast it.

 Hmmm. MTH has this built in. Maybe a good upgrade for Lionel to add?

But the reality is that there is a significant number of bad Legacy Bases out there.  On my Iowa/Tennessee trip I visited 17 train layouts, looked at Base signals with an oscilloscope on about half of them and found 3 clipped/distorted unloaded signals.

Why beat yourself up with Band-Aids when the Base is defective/weak?

I believe there is a need for both types of signal monitors, not just one.

If a suitably positioned voltmeter module on the traveling car was back-lit LCD or LED, perhaps a traincam could focus on the readout and also capture the background scenery to correlate location.  That way you could record and preserve signal strength around a layout using existing devices.

Adding to the idea of emitting an audio tone proportional to signal-strength, perhaps obvious but this is a "wireless" link back to the tester!  You could in fact record a test session using a PC microphone using existing software in any PC.  By pulling the traveling car at a fixed speed and starting from the same point on a layout, you could compare test runs.  For example, using freeware audio software two recordings could be played in stereo - one on the left channel, one on the right channel - to compare test runs.  Sounds complicated and it probably would be - but I think for few $ in parts (assuming you have an operating R2LC), the audio feedback method could quickly reveal reception issues if Dale's tester does not first identify a bad transitting base unit.

But if someone steps-up and designs an Arduino or whatever with a wireless link to a PC to record a test session and manage, analyze, plot data, etc. that would be a neat contribution to the hobby.

I fully agree with you Dale, I was suggesting this as a new solution to address the layout specific signal issues.  You have the base signal strength covered.

Dale,  Was this from people that called you that were having problems, or random sample of 17 layouts.  I think that matters.  You are reporting 33% failure of Legacy bases.  Unless this is just people with problems, than it is 33% of known problems, but you clearly don't know how many folks have Legacy Bases that are fine.  Your sample of failures could quickly get in to the 1 or 2% range.

Either way the on air would have far more value in my opinion, since even folks with perfect bases can make a layout non functional in construction.  G

Only one of the layouts was a known-beforehand problem layout - Lyle Dumont's in Iowa.  He also had a second smaller layout that had an OK Base.

One layout had 3 Bases mounted, but the one in use was the bad one.  The other 2 were OK.

Given the simplicity of testing the base drive with and without the layout connected, I think that test is very worthwhile. 

The other test we're talking about is really a totally different thing in that you're testing the quality of the ground signal around the layout, which is a huge variable, depending on the exact layout design.

I vote for the base test. I know about 9 bases intimately, and 2 of the bases were so weak that a modest layout (say 12 by 16) would not function correctly. AND those two persons were chasing non issues all over their layouts for months. One sent the base back to Lionel and Lionel pronounced it good.

The trouble is that the base works...but not how it should on the whole layout. That causes the owners to go mess with the layout. In both cases, when the bases were restored to "full" output, the signal coverage was solid everywhere.

I went through the effort of providing a feed-through 9-pin connector so that my unit can be permanently attached to the Base without losing any functionality.  The user only needs to turn on the meter to verify that everything is still good.  It would be cheaper and easier to just provide a pin to stick into Pin 5, but keeping the layout in "normal" configuration seemed much better to me.

I vote for the field signal detector. I have a complicated layout which is getting more so every day. My TMCC base seems to be working just fine, as some of my engines navigate the layout without trouble.

I do have a Legacy base, which I have never gotten to work. But because my focus has been on construction, and not operation, dealing with it hasn't been a priority. With what Dale has said here, it makes me wonder if I got a dud. I have to say that Legacy has become more interesting since Lionel has made the codes public.

There is the known issue of the unshielded coil on the railsounds board which is causing some of the problems. That fix is pretty straight forward. The hand over the engine test is a good indicator for that problem.

In the end, all I ever wanted was smooth reliable operation. If I had that, the possibilities would be endless.

Very interesting.  Not a significant sample size, but doesn't bode well for the reliability or durability of the Command Base.

I guess knowing the normal signal strength as designed, than honing in on the minimum acceptable level for the base to be considered operable is key to declaring a base good.  I imagine that latter is where the science will come into play as the size and construction of the layout will effect that minimum threshold needed.

If I was as smart as you are with electronics Dale, I would build a LED sensor that plugged into the base, that still allowed the port to be used. (Like the Fuel Sensor gauge on a propane tank)   The indicator would constantly monitor the base output.  Green is good, yellow is degraded and red is bad.

Your initial data implies that maybe a necessary requirement.

The Field sensor is also required and would be used during the construction and also would be used to test potential changes to the layout.   G

So If you send a base back to Lionel, How do they test them ?

Maybe we can find out.

I'd probably consider the A/D channel of something like a PIC or Arduino to monitor the DC level and light the appropriate LED.  A pretty simple program would create the proper LED display. 

I think there's a chip that does that. Icom transceivers for example use a voltage level to  output band data...what band it's tuned to. And I remember using a chip to decode that into a number of descrete outputs...eight in that case. I'll look for it just for curiosities sake.

Seems like these chips are used to convert analog level into a string of leds which could either light the lower level leds and keep them on or just light the highest one.

I left a phone message for Mike Reagan to see if maybe they should have at least one of my devices.  If people start sending their Bases to him for repair, along with the readings they got with my meter, he could verify their results and also verify the correction after repair.  That beats seeing if it runs a train on their test layout.

I had some interesting results at the TTOS meeting today.  I used one of my meters to measure the Legacy Base outputs for the two demo layouts at the meet.  Both loops were moderate-size oval layouts with 3 or 4 sets of concentric ovals. 

Both Bases read a nominal 2.00 volts unloaded.  When the track wire was attached, the readings rose to 2.05 and 2.35 volts.

My first thought is that the output filter on the Track signal benefits from a small amount of capacitance, and that is the reason for the rise.  The Legacy Base has a filter, but the TMCC Base does not

I think I want to open my Legacy Base and examine the output filter on the Track signal.  I also want to test my Base with small amounts of added capacitance at the output. 

I just opened my file of Legacy Base photos to look at the filter, and I see that I had to replace the .1uF capacitor output capacitor when I repaired my Base (in addition to replacing the blown output transistor with a beefier type.)  The Legacy output has a cylindrical multi-window ferrite bead at the output, and maybe a smaller surface mount inductor.  This requires closer examination.

2 volts seems pretty low, right?

No, 2.0 volts is the nominal meter reading of a 5V p-p signal after accounting for the diode drop, half-wave rectification and the meter's characteristics.

OK, I guess I needed to look back at the start of the thread.