R2LC Serial Data Buffer

I was looking just today at the Cruise M for use in a project.

Just out of curiosity, did you originally connect the Railsounds Commander and the Cruise M in parallel, so they both feed from the R2LC, or did you use the Serial Data Out on the Cruise M (pin 2 on J4) to feed the Railsounds Commander? 

First I connected them in parallel, then I tried the serial-out on the CC-M, didn't work.  That's when I broke out the 'scope to see why.  I didn't check the serial-out with the 'scope, but wired directly to the RS Commander, it acted like it wasn't there.  The CC-M worked fine, so it was getting serial data.

I think the new CC-M that's the "universal" one has no problem with the parallel connection, this was the earlier version.  I had several that were still in the wrap from several years ago.  Obviously, there was a change as I've done this with the latest version without an issue.

John, This was the fix for the IR tethered version.  You sure you had the correct CC-M. The new ones have the attenuated signal.  This is not suppose to happen on a diesel.  I have not seen this issue occur on diesels.  Maybe a bad ERR RS Cdr?  G

George, you did see that I said these were the previous version of the CC-M, right?   This also happens on the TMCC back-EMF driver from Lionel parts, I tried that one as well, same problem.  Like I said, I have used the new "universal" ones without issue in the same configuration.

I am curious what is different about the serial data output, I'll have to look at that some day.  I figured that would solve the problem, but the RS Commander acted like the serial data wasn't there when I connected that.

Interesting, I have a repair in form Len B on this here forum that is showing an intermittent issue that is exactly these symptoms. I have yet to be able to replicate the issue after several running sessions

Does it use the new ERR RS Commander?  I don't know if I'd have the same issue with the older RS4 boards, didn't check.

John, did you hit the 5V from pins 19-20 on the R2LC and the other to serial pin 24?

Yep, I used pin 20 for the 5V power and pin 24 for the serial data.  The output of the buffer feeds the RS Commander.  With that installed, everything works fine, and the serial data has an additional volt + of amplitude, obviously the RS Commander imposes more of a load than I'd expect for a new product.  I'm guessing it's feeding an opto-isolator as the rest of the circuit's DC ground is NOT common with the frame ground like TMCC.

John,  are pins 3&4 on the R2LC using frame ground?  You say it is just using ground from board and not shared frame ground.

Of course they are Marty.  

What I said was the new RS Commander doesn't have DC common and frame ground connected.  The RS Commander has a full wave rectifier directly after the track power comes in, so any attempt to ground any pin but the incoming power pin will allow the magic smoke to escape.  That is different than the R2LC that uses a half-wave rectifier and has it's DC signal common the same as frame ground (wheels)

Got ya

gunrunnerjohn posted:

George, you did see that I said these were the previous version of the CC-M, right?   This also happens on the TMCC back-EMF driver from Lionel parts, I tried that one as well, same problem.  Like I said, I have used the new "universal" ones without issue in the same configuration.

I am curious what is different about the serial data output, I'll have to look at that some day.  I figured that would solve the problem, but the RS Commander acted like the serial data wasn't there when I connected that.

No I did not see a call out on version, but since this is diesel I would not have thought it would matter except the new RS from ERR seem to need a stronger signal.  I think this is an issue with the Sound CDR requiring a stronger signal, and I think that is what they must have modified on the new CC-M.  Even the older board for dummies no longer supports Rail Sounds with the newer sound board.  G

I suspect my little emitter follower may be more useful than I imagined.  Now that I see how easy it it to whack one together, that will no longer be an issue.  Of course, for the dummy locomotive board would have the issue of finding a source of 5V to power the circuit.

It's clearly the sound board that is stepping on the signal, it drops the amplitude of the serial data from a bit over 4V p-p to around 3v p-p.

Funny you say "my"  It was part of ERR solution originally G

I couldn't find the reference to the ERR solution, since it was an independent invention, it's my solution.   I thought that ERR only had issues with the wireless tether, I didn't realize they had issues with an all wired solution.

Sure you have it, you gave me a an old copy of the diagram.  Boxcar Bill had posted at one point.  They do have issues with some board sets not working with newer 5.0 sound sets.  Mini CDR EX is one.  Would drive 4.0, but not the new ones now.  CC-M also.  So the "solution" which amplifies Serial Data is certainly going to fix any of these issues I think.  G

Must be that old age setting in.