Trains.com

Subscriber & Member Login

Login, or register today to interact in our online community, comment on articles, receive our newsletter, manage your account online and more!

Bus termination

700 views
3 replies
1 rating 2 rating 3 rating 4 rating 5 rating
  • Member since
    July 2010
  • 126 posts
Bus termination
Posted by grinnell on Sunday, March 6, 2011 3:44 PM

I've read the wiring for DCC site where it discusses the need for RC termination of long bus wires, however I need advice in one situation. I have a power district where the bus goes 26 feet in one direction and 35 feet or more in the other dirtection. It's the 'or more' that is the problem.

At the 35 foot end there is a drop to a toggle switch that allows me to shut off the power to a staging track bus that extends another 15 feet. I'm stuck with the locations for the booster and the toggle switch, so as a result, sometimes that leg is 35 feet long and sometimes it is 50 feet long.

So where do I put the RC termination? At the 35 foot point, the 50 foot point or both?

Thanks

Grinnell Jones

  • Member since
    December 2001
  • 1,932 posts
Posted by Stevert on Sunday, March 6, 2011 4:16 PM

Grinnell,

Use a DPDT toggle. 

Wire the main bus to the center terminals, a terminator to one set of terminals (ie, the "up" toggle position), and the extension with termination to the other set (ie, the "down" toggle position).

With the toggle "up", the main bus is connected only to the terminator.

With the toggle "down", the main bus is connected to the extension, which is terminated on it's far end.

  • Member since
    February 2002
  • From: Reading, PA
  • 30,002 posts
Posted by rrinker on Sunday, March 6, 2011 5:35 PM

 Do you locos behave oddly near the end of the line? Miss commands, take off by themselves, etc? If not, you don't need any terminators. DCC is quite forgiving and what may look like a compeltely junky signal to an engineer used to making sure there was always the cleanest possible signal is probably well within the tolerance of what the DCC signal is and what decoders can respond to.

 Our club modular layout is 14x100 feet. It's divided into 3 sections, none of those bus runs have terminators yet each one is over 75 feet. There are no problems with control.

                      --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    July 2010
  • 126 posts
Posted by grinnell on Sunday, March 6, 2011 6:06 PM

Stevert

Use a DPDT toggle. 

Wire the main bus to the center terminals, a terminator to one set of terminals (ie, the "up" toggle position), and the extension with termination to the other set (ie, the "down" toggle position).

Great idea, thanks.

It'll be a little more complicated because this section is the far side of a serial staging reverse loop so I was already going to use a DPDT center off switch to reverse the polarity (Up is inbound, Down is outbound). I guess I can use 2 DPDT On-On switches: one labeled On-Off with the terminator wired to the "OFF" position and then the second DPDT switch labeled "IN-Out" to swap the polarity.

This section is going to be built soon and I'm trying to figure out a design so I can order the parts.

Subscriber & Member Login

Login, or register today to interact in our online community, comment on articles, receive our newsletter, manage your account online and more!

Users Online

There are no community member online

Search the Community

ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT
Model Railroader Newsletter See all
Sign up for our FREE e-newsletter and get model railroad news in your inbox!