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@Jerryrails posted:

I don’t think I understand any of this but it seems that you are all suggesting I could now use the MTH WTIU and the Lionel Base 3 on my new layout and get them to work together. I just need this gizmo being discussed? Is it doable for someone like me? Is there a path to a hand holding list of directions? I would like to run both Legacy and DCS

Patience grasshopper, it's being fine tuned.  I think it'll be soup soon.

@Jerryrails posted:

I don’t think I understand any of this but it seems that you are all suggesting I could now use the MTH WTIU and the Lionel Base 3 on my new layout and get them to work together. I just need this gizmo being discussed? Is it doable for someone like me? Is there a path to a hand holding list of directions? I would like to run both Legacy and DCS

So we already run Lionel and MTH/DCS in our club and in most cases with some fine tuning (GRJ's booster, some signal level adjustment) it works pretty well. I would imagine for a home layout that's enough to get you going.

The problem is this stuff is both locomotive and weather dependent so in a big club with lots of trains and lots of members there are isolated cases where a particular locomotive doesn't work well in a particular part of the layout (and often only in particular humidity levels). The work we're doing on this new suppressor idea is to try to solve those edge cases. We're sharing the progress as we test it out so the other folks with large layouts can share in what we find and learn

@Adrian! posted:

So we already run Lionel and MTH/DCS in our club and in most cases with some fine tuning (GRJ's booster, some signal level adjustment) it works pretty well. I would imagine for a home layout that's enough to get you going.

The problem is this stuff is both locomotive and weather dependent so in a big club with lots of trains and lots of members there are isolated cases where a particular locomotive doesn't work well in a particular part of the layout (and often only in particular humidity levels). The work we're doing on this new suppressor idea is to try to solve those edge cases. We're sharing the progress as we test it out so the other folks with large layouts can share in what we find and learn

Where I think this is going to help me personally is with our modular club.  Since the wiring is hardly "DCS inspired", the signal levels are not optimal in any case.  If this can aid in some way improving the DCS signal quality, that would be a great help.

Cool, that works.  Any thoughts on trying shielded inductors vs unshielded?

I mean step one is to try this one out on the layout tomorrow and see how it goes. If it's helping the DCS performance then I can do a production run... if it totally sucks (as I expect) then I think my next step is hole thru scale components. I mean shorting out my 50 ohm sig gen is a lot easier than shorting out the ~10 ohms of source impedance I measured between the rails.

With a good ferrite core inductor you can get ~20uH or so with a series resistance like 0.01 ohms or so. Then use tantalum caps so the ESR is very low too. That drives the general look of it from the $1 to $15 regime, and the 0.3" scale to the 2" scale, but whatever, it needs to work, right?

@Adrian! posted:

With a good ferrite core inductor you can get ~20uH or so with a series resistance like 0.01 ohms or so. Then use tantalum caps so the ESR is very low too. That drives the general look of it from the $1 to $15 regime, and the 0.3" scale to the 2" scale, but whatever, it needs to work, right?

I'm not as worried about the final price as I am about the effectiveness of the filter.   We spend thousands on the layout and locomotives, etc., so spending a bit more to make them run right doesn't seem to be much of a sacrifice.

OTOH, regarding perfect being the enemy of good enough, it depends on how much more effective the additional cost makes the filter.  If we get 90% of the benefit from a $2 parts cost that we could get from a $15-20 parts cost, then it might make sense to do a volume run of the $2 board.   I am thinking that the boards would incorporate two sets of filters in parallel if the parts only cost a couple bucks, that would help with the performance it appears.

I'm not as worried about the final price as I am about the effectiveness of the filter.   We spend thousands on the layout and locomotives, etc., so spending a bit more to make them run right doesn't seem to be much of a sacrifice.

OTOH, regarding perfect being the enemy of good enough, it depends on how much more effective the additional cost makes the filter.  If we get 90% of the benefit from a $2 parts cost that we could get from a $15-20 parts cost, then it might make sense to do a volume run of the $2 board.   I am thinking that the boards would incorporate two sets of filters in parallel if the parts only cost a couple bucks, that would help with the performance it appears.

It seems to be uniquely the model train people in our club that pour $2900 into a locomotive, then immediately spend a month complaining about smoke fluid costing $19.

@Adrian! posted:

It seems to be uniquely the model train people in our club that pour $2900 into a locomotive, then immediately spend a month complaining about smoke fluid costing $19.

Actually, that's pretty universal.   I had a discussion with a guy about looking for smoke unit home brew recipes for his fleet of Legacy steam locomotives.  He couldn't understand my stance of simply buying a couple big bottles of JT's Megasteam and using them until I needed more!  He was sure he could save money by mixing up who know what to pour into his engines.

@Rod Stewart posted:

So Adrian, are you saying that something like 5.9 to 6.0 nF is about right and gives us the magic 455KHz notch?

So the ideal value is lying between two standard values (5.0nF and 6.8nF) , so I split the difference like this:

(22uH)--(5nF)--(22uH)--(6.8nF)--(22uH)--(5nF)--(22uH)--(6.8nF)

The effective cap is then the midpoint between those values and yeah its very close to 450 KHz. As I posted earlier... the concept is "working kind of" we still have some issues with the design in terms of series resistance so I'm going to work out a rev 2 with less lossy components.

I'll of course share that when I have it done

I did a quickie layout, I'm shooting for a compact footprint so it can be easily installed in a locomotive.  Since there's no chance I'd have an IR oven to build these, small quantities will be hand assembled, and a larger quantity would be sent to a PCB house.  That being the case, I did a 2-sided design for compactness.  Since it's assumed that these would likely be employed in parallel, I have a jumper between the front and back that can be installed to parallel two filters.  Since this is a prototype, I could leave that out if it turns out that's the default configuration and just connected them always in copper.

I found inductors with a .3 ohm resistance, considerably better than the first ones used.



DCS-TMCC Notch Filter R1.1 Schematic

DCS-TMCC Notch Filter R1.1 BOM

DCS-TMCC Notch Filter R1.1 3D Top

DCS-TMCC Notch Filter R1.1 3D Bottom

Attachments

Images (4)
  • DCS-TMCC Notch Filter R1.1 Schematic
  • DCS-TMCC Notch Filter R1.1 3D Top
  • DCS-TMCC Notch Filter R1.1 3D Bottom
  • DCS-TMCC Notch Filter R1.1 BOM
Last edited by gunrunnerjohn

I did a quickie layout, I'm shooting for a compact footprint so it can be easily installed in a locomotive.  Since there's no chance I'd have an IR oven to build these, small quantities will be hand assembled, and a larger quantity would be sent to a PCB house.  That being the case, I did a 2-sided design for compactness.  Since it's assumed that these would likely be employed in parallel, I have a jumper between the front and back that can be installed to parallel two filters.  Since this is a prototype, I could leave that out if it turns out that's the default configuration and just connected them always in copper.

DCS-TMCC Notch Filter R1.1 Schematic

DCS-TMCC Notch Filter R1.1 3D Top

DCS-TMCC Notch Filter R1.1 3D Bottom

Happy to report there was some initial testing at the AGHR club. This configuration of 2-parallel of the SMD ones like you have here works "pretty well" but not "perfect". I'm lazy and don't want to do it all again, so we might try just doubling up (4-parallel) what we have before we revisit.

I also tried discrete components, but the notch gets really pointy and hard to align. A tunable L or C may be the next step there, but like I said the SMD ones are getting us 95% of the way there already (plus the cost and difficulty of the installation is so much lower)

@Adrian! posted:

Happy to report there was some initial testing at the AGHR club. This configuration of 2-parallel of the SMD ones like you have here works "pretty well" but not "perfect". I'm lazy and don't want to do it all again, so we might try just doubling up (4-parallel) what we have before we revisit.

I also tried discrete components, but the notch gets really pointy and hard to align. A tunable L or C may be the next step there, but like I said the SMD ones are getting us 95% of the way there already (plus the cost and difficulty of the installation is so much lower)

I think in general that SMD components tend are a little more consistent than thru-hole components, at least that's been my experience.  I'm going to order some PCB's for this configuration and do a little bench testing.  I dusted off my sweep generator, it's been in hibernation for several years.  I wanted to make sure I had the ability to do the bandwidth testing.

As for the 90%-95% achievement, perhaps we don't want perfect to be the enemy of good enough.   It sounds like trying to go that last little distance may be exceeding the point of diminishing returns.

Last edited by gunrunnerjohn

I think in general that SMD components tend are a little more consistent than thru-hole components, at least that's been my experience.  I'm going to order some PCB's for this configuration and do a little bench testing.  I dusted off my sweep generator, it's been in hibernation for several years.  I wanted to make sure I had the ability to do the bandwidth testing.

As for the 90%-95% achievement, perhaps we don't want perfect to be the enemy of good enough.   It sounds like trying to go that last little distance may be exceeding the point of diminishing returns.

I'm an academic and a researcher

It needs to be perfect or it bugs me on the inside. Until DCS has the same responsiveness with the legacy base on as it does with the legacy base off, I'm always going to have a bad feeling on the inside when running trains

@Adrian! posted:

I'm an academic and a researcher

It needs to be perfect or it bugs me on the inside. Until DCS has the same responsiveness with the legacy base on as it does with the legacy base off, I'm always going to have a bad feeling on the inside when running trains

You're right, you're doomed to be bugged by most things in the outside world!   I'm happy if I can solve a problem.  If everything runs great, I'm not that concerned what the 'scope is telling me.

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       REMINDER

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Just to reiterate for everyone reading this (and those emailing). 99.9% of the people here will not need this device. It only solves one very specific problem:

If you find your DCS is unresponsive with the Legacy ON, but works fine with the Legacy OFF,  especially in certain spots of a layout or with specific engines then this might help you. It will not be helpful in any other weak control signal situations. It doesn't make DCS stronger or Legacy stronger, it just helps keep them separated in the same layout.

Actually, I've personally seen this on both Harry Henning's large layout at his house and on our modular club layout, so I suspect the percentage that will benefit is a bit more then 0.1%!   I do notice even on my fairly small 12 x 24 layout that I sometimes have trouble adding engines, but switching off the power to the Legacy base allow them to add.  I usually isn't a problem, so I never chased it down, but this might be the solution.

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