# Other end of the bus?



## timdrum (Nov 24, 2012)

Hey guys, 

Quick question... For DCC, where does the "other" end of the bus wire connect to? I know it starts at the booster and follows the track, but where does the ramaining end go? I've tried finding out at several sites and maybe have just read into wrongly, but I'll be setting up soon, and have no clue where to connect it! It's a 4x8 layout, HO...  Thanks for anything!


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## waltr (Aug 15, 2011)

The last set of track feeders would go on the end of the bus.
If the bus wires are longer that doesn't hurt. Just tie them up out of the way and ensure the ends can not short together.


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## broox (Apr 13, 2012)

To add to Walt's reply, in some circumstances (long bus runs, nearing 10m /30ft) you may need to terminate the bus with a simple circuit, consisting of a capacitor and a resistor.



> There are problems with long bus wire runs. The problems are difficult to describe without a background in radio or an electrical engineering degree. It would take a lot of explaining and you would have a bad headache. You don't want a headache and I don't want to give it to you. Furthermore, to really see the problems requires an oscilloscope — a tool few model railroads have.






> Solution for unterminated bus ends:
> 
> The name of this problem suggests the solution - terminate your bus ends. This is simple and inexpensive to do. Just put this "RC network " at each end of your long buses. Yes, you will need two of these circuits for each bus — one at each end.
> *image and table on website*


http://www.wiringfordcc.com/track_2.htm#c2


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## NIMT (Jan 6, 2011)

There is some that think the end of the bus need to be terminated to a resistor and or capacitor. I personally have never done that and think that it would cause more problems than good!:sly:
My only suggestion in do not run it all the way around in a loop back to itself! When feeding a loop of DCC track start from the command station and run half around both ways, without connecting them together where they would meet. I'm still not sure that it would be a real problem because the track connects all the way around the loop doesn't it!


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## broox (Apr 13, 2012)

Wouldn't it be path of least resistance or something? making sure the power goes to the track instead of staying on the bus? (I haven't thought this through, just top of the head thoughts)


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## timlange3 (Jan 16, 2013)

Broox, no capacitor, why do you need to store energy? As for a resistor, a several inch air gap is a very good resistor! Usually the end of the bus will just go to the last set of feeders.


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## broox (Apr 13, 2012)

I was just referencing the quoted website. reckons you can get issues with the dcc signal at a bus length of around the 10m /30ft mark.

Is it nothing to worry about? he had pretty pictures and graphs and everything...

I don't know enough about the technicalities of it to dispute what he's written, I was just passing along some (relevant?) info.


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## Brakeman Jake (Mar 8, 2009)

Digitrax recommends that we shouldn't connect both ends of the buss wires where they meet.It's not necessary and would make troubleshhoting more difficult should a problem occur.
Then I read somewhere else that it's not a bad idea to twist the buss wires together between feeders to protect against possible radio interference.True?I don't know.I've installed multiple lengths of buss wires under the club's layout and didn't do it.No problems reported yet.Who's right?


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## waltr (Aug 15, 2011)

There is Theory and then there is what works in practice.
Since I do electronic design I know about the theory described in above posts.
However, in actual practice the DCC bus is not that critical on almost all layouts.
If the layout is huge and powering many loco's at once then the DCC bus may need to be put together with some of that Theory put into practice.


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## timdrum (Nov 24, 2012)

Thanks a lot for everything guys. I'm installing them in a few weeks so I'll put these answers into practice and hopefully, if I do them right, it'll run well!:thumbsup:


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