splitting DCS signal

Hi Clem,

#2 is better.  You want to make any wire splits close to the TIU (within 8 ft of wire run from the TIU is ideal).  This avoids signal reflections due to changes of impedance wherever there is an electrical joint.

 I didn't follow this one. I have a terminal block that's on the opposite side of the basement. It only splits into two short feeds, going to a single mainline broken into blocks. I have no signal problems there so I may not touch it!

Clem,

#1…….Is it better to run one wire to that point, then split into two feeds at terminal block?

     Or

#2……..Run two wires from TIU output?

in practice, there's no real difference between #1 and #2, as long as there is no more than one split in the wire pair that is connected to the output of any TIU channel. Consider the following:

• Wiring from a TIU channel output to a terminal block that then splits the signal into multiple pairs, each pair then going to a track block, is OK
• Splitting the output of a TIU channel directly into multiple pairs, each pair then going to a track block, is OK
• Wiring from a TIU channel output to a terminal block that then splits the signal into multiple pairs, where one or more pairs is then split again before going to a track block, is not OK
• Splitting the output of a TIU channel directly into multiple pairs, where one or more pairs is then split again before going to a track block, is not OK.

This and a whole lot more is all in MTH’s “The DCS O Gauge Companion 2nd Edition", available for purchase as an eBook or a printed book at MTH's web store!

Thank you

OK I will run two wires from one TIU channel to two separate blocks, no splits anywhere.

Clem 

I'm surprised at Dave's answer.

Kind of hard to do star wiring without running one wire to a terminal block and then splitting, isn't it???   Dave, obviously I respect your knowledge of DCS W-A-Y more than my opinion, but your answer is confusing - to me anyways.

thanks - walt

Walt,

   I know you were not directing this response to me, however follow Barry's directions

in his book for best results most of the time.  There are many ways however that you can run wiring and get away with having all 10's on your layout, I have even use a double terminal block coming from one TIU channel, definitely not a recommeded wiring set up, but in my case it worked running on about 5 different levels, the truck was the magic lights.  I did this to eliminate the purchase of another TIU, if you test as you build you can cheat a might on different engineering principles when building a DCS layout.  I do suggest for a beginner or a mid level experienced runner, that you

use Barry's book to reference while building a DCS layout.

PCRR/Dave

Walt and Dave I would have thought #1 also

My layout was working really good, when measured with a single locomotive I get 9 and 10 all around. Then when I started running four trains on my one loop and three of those where lash ups of three locomotives then use push the all button!  signal not so good.  You can only cheat wiring so long, Now is time for me to improve. Once I get the 300 feet of single track mainline one loop done, I get to do the yards one one each side of display (20 feet apart) Also moving TIU to more central location close to ceiling.

clem

PCRR/Dave: Dave, I've been using DCS since it originally came out.  I'm very comfortable with my wiring scheme as I have followed Barry's advice about star wiring from when he first started pushing it.

I was more asking Dave why his answer seems to contradict the star wiring theory.  But possibly Dave was being very specific for this one question and one situation and felt for THIS ONE application his suggestion would be best.

thanks

- walt

Walt….. I think your right that is why I'm incorporating #2

clem

Walt,
I understood it as having the terminal block close to the TIU. If there is a 20 foot run, don't put the terminal block at 18' and run the pairs 2' to the tracks, rather have the terminal block at 2' and run the pairs the 18' to the tracks.

Guys,

I understood it as having the terminal block close to the TIU. If there is a 20 foot run, don't put the terminal block at 18' and run the pairs 2' to the tracks, rather have the terminal block at 2' and run the pairs the 18' to the track.

I would disagree.

IMO, when given a choice between short runs from the TIU to the terminal block vs. the terminal block to the tracks, make the shortest runs from the terminal block to the track blocks.

Notwithstanding any signal reflections, which will typically have little or no real (vs. theoretical) affect on the DCS signal (particularly when using a Rev. L TIU), there's simply less work and less wire when doing things this way. 

IMO, when given a choice between short runs from the TIU to the terminal block vs. the terminal block to the tracks, make the shortest runs from the terminal block to the track blocks.

This is not suitable if you also run a lot of conventional trains.  For such use, optimal operation necessitates having many insulated blocks, each controlled by a toggle switch on a central panel.  The result is more like Lima's description, with the "terminal block" being about 2' long as the feed goes from toggle switch to toggle switch.

I feel that it is essential to use adequate gauge wire.  For a 20' run, I would use 14 gauge.

Clem,

   Barry as usual is absolutley correct, when you violate the rules and use a split block set up, you want the wires run from the spilt terminal blocks, to the tracks, to be as short as possible, wiring the other way degrades your DCS signal almost twice as much.

Also it is my recommendation to put a magic light at the end of each split terminal block and track side also, if you want to run with all 10's, thru out a multi level layout.

I tried a few alterations to Barry's engineering down thru the years, all I can say is make darn sure you test as you build, multi splits with longer than 3' wiring can really degrade the DCS signal, especially without using any magic lights.

PCRR/Dave 

Think it is difficult to have switched blocks this way unless it is an island layout because the wire to the switch has to first run all the way from the terminal block near the tracks to the switch and then back out to the track again. Any large around the room style layout would most likely face the same issues due to the distance from either the TIU or the terminal block. Either a short feed to the block and then out to the track or a long feed out to the track and then doubling back to the other blocks. At 12-15' per block after 3 blocks you are at 45' real quick. It is interesting to see how many different "wiring systems" are in use yet they all work!

One thing we do know, it is impossible to get eight terminals on a TIU binding post and still tighten that little knob

Lima,

   Say man if all you wanted was 8 you were doing well, how about 24! Your point is well made and IMO for most runners its a lot better to design your wiring as Barry's book advises, lots less hastlement in the long run.

PCRR/Dave

Lima,

Use relays instead of toggle switches.

Relays are much more expensive than toggle switches and more susceptible to failure.  I have 70 blocks.  All are fed through a central control panel, each with a toggle switch, with a lead running from the switch to the block.  Everything works.

To further confound the naysayers, common is fed to all blocks and to all accessories from a 12-gauge bus loop the goes around the layout and is tied at each end into all transformer U posts.  I also have the layout wired semipassive:  ground is not fed through the TIUs, but all black TIU terminals are tied into the ground system.

DCS is much more forgiving than many think, but if you really want to cut down signal, feed a block with 18-gauge.

WOW!  And to think all that I THOUGHT that I was doing was asking Dave H. a simple opinion question!

But it was enlightening and fun reading!!!!

Ironic though that there were a lot of forum regulars that replied but NOT the one that the question was directed towards.

- walt

Walt, after all these years on the forum, you should know that a simple question will engender hundreds of posts.

Walt,

Ironic though that there were a lot of forum regulars that replied but NOT the one that the question was directed towards.

Clem's question wasn't addressed to anyone in particular.

Once again I realize that omission of a word or 2 changes my intent: I meant MY question of Dave H.

Someday I'll learn!

- walt

How about omitting the word "not" from a direction?