Skip to main content

An odd issue cropped up here today, and after chasing it down, I thought others might be interested in the solution.

I'm installing a Cruise Commander M and the new ERR RailSounds Commander in a diesel.  I'm specifically using the CC-M so I can use the ditch light feature, I used a simple motherboard for the R2LC and just custom cabled it.

All was going just great until it came time to do the first test!  I fired it up, programmed it, and flipped the switch to run.  Everything seemed fine, sounds worked, couplers worked, so I cracked the throttle.  AWAY WE WENT AT FULL SPEED!  OK, that's not good.  I tried programming it again, and yes I did set the locomotive type!  Same issue.  Swapped in another CC-M, no change, new R2LC, ditto.

Time to break out the 'scope and see what's going on.

When I plug in the new ERR RS Commander, it really attenuates the serial data signal, it's less than 3V peak.  Apparently, the CC-M has an issue with this and doesn't see the serial data.  Mystery solved, but what do I do to fix it?

Enter the R2LC Serial Data Buffer.  I added an emitter follower buffer to isolate the serial data from the RS Commander, problem solved.  I technically didn't need the 470 ohm resistor I suspect, but I have an aversion to putting a potential high current source on an input, and it's cheap enough to add.  I tapped the 5V and serial data from the R2LC, and I added the 2.54mm connector for the serial data to the RS Commander.  This allows me not to modify the cable itself for the RS Commander, and I can also easily disconnect it.

 

Attachments

Images (2)
  • blobid0
  • blobid1
Original Post

Replies sorted oldest to newest

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.

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.

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.

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)

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

Last edited by GGG

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.

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

Add Reply

Post

OGR Publishing, Inc., 1310 Eastside Centre Ct, Suite 6, Mountain Home, AR 72653
800-980-OGRR (6477)
www.ogaugerr.com

×
×
×
×
Link copied to your clipboard.
×
×