DCS and wiring

Art;

Since no one has jumped in yet, I'll offer a few comments.

First, not sure why you want to run DCS in passive mode?

DCS and Legacy will play well together, with the Legacy base cabled to the TIU using the MTH cable.

Each TIU channel will handle 10 amps or 180 watts of power. This is enough to run several trains on each, or at least two long passenger train with incandescent lighting.

You could easily run your lower level on one fixed TIU channel and the upper on the second fixed channel. Observe the 250 feet track limit per channel.

You should observe the star wiring guidelines using a distribution block for each channel. You should also observe the 10-12 track pieces per power feed, and no more than 10-12 feeds per channel/distribution block.

On my layout the common outside rail returns are all buss wired, and it seems to work just fine.

I power 400 feet of track total using all 4 TIU channels and magic bulbs with an older rev I3a TIU. The two variable channels are set to fixed. I get mostly 10's, with an occasional 8-9. I use lighted bumpers at the end of several sidings where the signal previously was poor.

 

Hope that helps,

Rod

Art,

 

While DCS is a lot more tolerant of most wiring schemes than is advertised by MTH, star or home run wiring is almost guaranteed to give you the best possible DCS experience.

 

Your proposed wiring scheme may work just fine, however, if you're building a new layout the absolute best way to go is star wiring. The additional increment in effoft is offset by the fact that you'll know that your DCS signal strength will be maximized if you follow the wiring guidelines in The DCS O Gauge Companion.

 

As regards passive TIU mode, what do you believe that you'll gain? On the negative side, it's more work, you lose the use of variable channels in variable mode and you lose the E-Stop function.

My question is this- can I get away with 4 blocks and bus wiring otherwise I would need 12 -14 blocks and a whole lot more complicted wiring?

 

I 'd bet you can. Use a tiu channel for each block, Only one way to find out though... hook up one block, then another etc.

thanks to all for your reply and to Barry your book is an excellent source - glad I have it. The reason for using DCS passive is as follows: I run conventional, Legacy and DCS. The starting voltage is to high for modern can motors but with Legacy or TMCC I can start from zero. In the passsive  mode I can overlay DCS signal on any channel. At least this is what I am trying to accomplish. I did not realize that I can set variable to fixed. Would appreciate more info. If not, I am sure it is in Barry's book.  Art

Art,

The starting voltage is to high for modern can motors but with Legacy or TMCC I can start from zero

To do that you'll need a TPC or Power Master for each channel. Regardless, why run modern stuff conventionally at all?

I use common bus with no problem, with frequent out rail drops and the ground for accessories.  I have much larger "loops" than you do, and use one TIU channel for each  It's not hard to break up into 3-4 blocks per loop, and gives considerable opertaing benefits.  Just run a length of 14-gauge (what I'd recommend on a layout of your size) to each blocks and sever the center rail between blocks.

 

Can motors are not current hogs.  I don't know why you say they need high starting voltage,  You should have had the old Lionel Pulmor motors.

Iwill not be running modern in conventional. I do like to run conventional locos from time to time and when I run a modern conventional engine such as williams ( with can motor) the 5 volt start speed is about 25 scale mph. i AM NOW SPOILED WITH DCS and want to start with 0 volts so these engine won't jack rabbit.  Therefore, using my second gen ZW with built in power master- 180 bricks and legacy or tmcc I can start at a more realistic speed.  I have TMCC,Proto 2, Proto 1 engines as well as conventional.  The Proto 2 are my favorite therefore DCS is a must.  Thus my decision to set TIU in passive. Have not tried it yet but will try to hook it up this weekend. M any of you have much more experience in this than I do so I am asking do you see any problems with this arrangement?  again thanks for the input.

I should have said I will not be running command engines in conventional.

Art

One way to solve that issue is to stick a diode string in series with a motor lead in the locomotive.  A couple of 6A bridge rectifiers will drop that 5V starting voltage to around 2V and give you the slow start you desire.

ARt, if you have a Williams that starts that fast at 5 volts, you are inputting too much voltage to the TIU variable, resulting in a highly deformed AC wave.  Cut the input voltage wat down and I think you'll be happy.

I have a medium sized layout that is already setup with Lionel Legacy and TMCC.  I used bus wiring as recommended by Lionel, with drops about every six feet.  Power is feed to the track by the use of Powermasters and Direct LockOns.  I would like to add MTH DCS to the layout, but with the current setup is that possible, as I really don’t want to give up the Powermasters and Direct LockOns.  I was thinking that with my current setup the DCS system could be added but hooked up in passive mode as no track power needs to feed thru it.  Am I right in my thinking?

 

Thanks,

 

Ed Kempf

You can hook up in passive and it will generally work, but with limits:

You have a Buss wired Layout and no blocks.

All those drops send the DCS signal to the track, and the signals go both ways from each power drop. Now they are all crossing one another, this results in the tower of babel for electronic communication.

So you need to break the center rail between each power drop. That will keep the signals from crossing and all will be well. Isolate your sidings as well.

Be aware that passive does not put quite as much signal on the layout, but with a Rev L TIU (Current Version) you should be fine.

So I am a little confused. Where is star or home run wiring any different, the signal will still go both ways with each drop that goes back to the terminal block. Unless you want or need separate power districts there is no need for blocks, isn't that the beauty of command control; be it DCS, TMCC or DCC.

Get rid of the TMCC Direct Lockons, they will kill the DCS signal!  I had the problem, and then at our modular club, we had the same issue.  Yes, both locations had a Rev. L TIU.

YThe difference is that a blocked plan ensures that a DCS engine never sees more than 2 occurrences of a DCS command, and it only sees 2 when straddling 2 blocks.

This question is mostly directed to Barry.  I am confused about the various wiring methods. I want to understand why a star or home run wiring scheme is really any different that a bus wire with drops to it. A terminal block (such as the MTH 12 or 24 port version) is nothing more than a very short bus. Potentially all the drops that feed back to the terminal block can be equal if not greater than the length of a single bus with short drops to it. Please take block wiring as you describe out of the equation.  I am not trying to start an argument, just trying to understand the basic difference. My experience with train wiring comes with HO DCC, and we use bus wiring in that scale as a common rule.

 

Thanks,

Ed Kempf

I agree with you, Ed, on your comparison of the terminal block to a bus.  My 70 blocks are fed from a control panel, with each having a toggle switch.  Power from the TIU outputs (I use 6) goes from toggle switch to toggle switch, and from the other terminal of each 14-gauge wire runs out to the block.  Common is fed by a #12 bare wire that loops around the layout.  It works.

I posted the above question on Jan 18th, and only one reply. I am wondering why no responses, did I ask a question that was a hard one to respond to.

Perhaps because you jumped in the middle of another thread.  Try a new topic and see if you can get better replies.  The short answer is it's not the length of the wires, but rather the difference in the propagation of TMCC or DCC signals vs. DCS signals.  The frequency of DCS is 3.27mhz, and the wavelength is much shorter than either TMCC or even DCC signals.  This means that loops created by the track and multiple bus drops can create standing waves and garble the DCS commands.