DCS Passive Mode, Club Modular Layout

First off, bus wired modules pose a special issue, we have the same issues with our modular club.  We're slowly trying to sort ours out, but we're not there.

One thing you can do to improve passive mode is to add a 22uh choke between the transformer and the track feed.

The question of how to fix it is a very complicated one, and it's most likely a unique solution for most different situations.

Next question - does passive mode work on all four channels?

Yes

Last question (for now) - can you add an engine in passive mode?  (unable to test due to RF out of Range issue above).

Yes  However, adding engines needs a pretty good signal or it will fail.

 Just how large is this layout ?  How many trains are running on each independent loop ? Have you ever tried hooking up DCS in the normal fashion ?   If yes. What was the result.
 My layout with some minor tweaking runs very well with DCS. It features pretty much common buss wiring.

 I thought the main reason for running in passive mode on large layouts. Was you were putting out a lot of amps to the track. More than the TIU was rated for. The DCS signal can only broadcast so far no matter how you hook it up before the signal goes south. If the layout is large. Passive mode will work. But you may need to block each loop and feed each block with separate channels. In which case. You may need multiple TIU ‘s in Super Mode. Don’t give up on the buss wiring. I’ve seen many layouts that work very well with it. 

Jim Harrington posted:

I tried this last night, and only had one PS3 engine to test with.  When trying to add the engine, I kept getting an RF out of Range message. When I connected the transformer power through the TIU, I did not get this error.  What could be the issue here?

gunrunnerjohn posted:

One thing you can do to improve passive mode is to add a 22uh choke between the transformer and the track feed.

I bet the signal was worse with passive mode and needs the choke.

I would have said to tether the remote to the TIU#1 and try to add. You said it worked in normal mode so you found the issue.

Do a signal strength test with a working engine. Make sure you don't have any signal killers on the rails. Check whole layout for power dip areas. That's also where there will be issues.

The National Capital Trackers found that in a modular environment DCS works much better with paired wiring. Each track has it’s own hot (Center) and return (outside),. The only place that they are tied together (common) is out the output side side of the TIU for Legacy TMCC.

Steve

Makes sense Steve, the DCS signal is an RF frequency, and having what amounts to a transmission line is probably the best idea.

In testing at the club a few years ago, I found that following a few DCC wiring standards seemed to improve the signal:

1. Make sure there is a break between feeds. This ensures that the signal doesn't loop back an cancel itself out.
2. Terminate the buss with a snubber (AKA Deats Filter). This prevents the signal from bouncing back along the buss.
3. Do not "close the loop" on the buss.
4. Center the TIU/Booster within the buss.

Adrian has the layout wired in passive mode, but I don't know the specifics on the current wiring, but a modular context is different as modular layouts operate off a full buss along the layout.

What rating should the 22uh choke have? (part number please).

I assume it gets wired on the hot output of the transformer?

Thanks,

Jim

Yes, to the hot side.  They have to handle the full current to the track.

I suggest the Bourns 2205-H-RC from Digikey.