Topics

Bus Length

Ron Haviland
 

HI to All,

 New to the group here, hoping you all can help fill in the blanks.

I had a small layout and tore it down last year to build a larger one. I will be adding an SB5 to my Power CAB. 

My question is: if you add a sub bus for occupancy does hat affect the the total length of the control bus? AT 5A I will be pushing the total length of bus runs at 36-40ft. from what I am reading if i add an RC filter and use 12ga solid  wire I should be OK, unless of the course you need to add the length of the sub-bus to that total. It seems to me however that it is running parallel to the main bus. 

Thanks!


dvollrath@...
 

Ron,
I'm assuming you mistakenly used the words 'control bus' instead of DCC track power bus. If you are monitoring the sub-bus for occupancy detection add a snubber/filter on that bus on the SB5 booster of the wires just before they go from the main bus through the occupancy detector. Putting a snubber/filter on a sub-bus after it has already passed through a current measurement occupancy detector will result in that track branch to register as always occupied.

DonV


---In WiringForDCC@..., <ronh56@...> wrote :

HI to All,

 New to the group here, hoping you all can help fill in the blanks.

I had a small layout and tore it down last year to build a larger one. I will be adding an SB5 to my Power CAB. 

My question is: if you add a sub bus for occupancy does hat affect the the total length of the control bus? AT 5A I will be pushing the total length of bus runs at 36-40ft. from what I am reading if i add an RC filter and use 12ga solid  wire I should be OK, unless of the course you need to add the length of the sub-bus to that total. It seems to me however that it is running parallel to the main bus. 

Thanks!


Steve Haas
 

>>>> My question is: if you add a sub bus for occupancy does that affect the total length of the control bus? <<<<

      That would depend on where you connect the sub bus to the track bus.  If you connect a 10 foot sub bus to the end of a 40 foot bus you have an effective run of 50 feet.  If you connect a 10 foot sub bus to a 40 foot bus just 10 feet from the booster you’ll only have a 20 foot run to the end of that sub bus.

>>>> AT 5A I will be pushing the total length of bus runs at 36-40ft. <<<<

      I’m curious as to where you got those specific limits.  The primary concern with long runs is voltage drop, this can be remedied to a point by using heavier wire.  The other concern is that the longer a bus run is the more likely the layout will have to deal with inductances issues.  These inductance issues can be greatly reduced by twisting those bus wires three to five times a foot.  If needed, a RC snubber can be added.  The other thing to remember is that a bus can go in two directions.  Placing a booster at the beginning of a 60 foot run might cause you some problems – placing that booster in the middle of that run results in two 30 foot runs – half the distance, half the problem.

>>>> From what I am reading if i add an RC filter and use 12ga solid wire I should be OK, unless of the course you need to add the length of the sub-bus to that total. It seems to me however that it is running parallel to the main bus. <<<<

      Filter won’t hurt.  For our purposes dealing with DCC power and data packets, there’s no difference between using solid and stranded wire of the same size.  With regard to total bus length, refer to my comments above; effective bus length = distance from booster to connection with sub bus + plus length of sub bus.

      Any questions? Give us a holler!

      Best regards,

      Steve

      Steve Haas

      Snoqualmie, WA

Ron Haviland
 

Thank you, most things I've read said the snubbers wont work at all on a detection sub.

Ron Haviland
 

Thank you Steve,
Your response concerning the location of the sub connection to the main makes perfect sense.

<<<<I’m curious as to where you got those specific limits.>>>>

           even with placing my SB5 near the center that's what my bus lengths will be. I do know about about twisting the pairs. Interesting that you say no difference between solid or stranded, I have read that stranded is not recommended for a power bus. At any rate solid is readily available to me.

Steve Haas
 

>>>>> Interesting that you say no difference between solid or stranded, I have read that stranded is not recommended for a power bus. <<<<<

      If I recall correctly, (and that’s a _big_ if), the difference between solid and stranded wire performance is miniscule at the power and signal levels used in DCC.  The difference can be significant in other applications.

      I prefer stranded as it is much easier to work with when running the buses. I also prefer to keep wiring as close as possible the framework of the layout so it doesn’t get in the way when someone has to get under the layout to do some work; a track bus leaving the main bus for that area will travel along an L-girder, turn 90 degrees to run toward the track in question, then turn 90 degrees and rise vertically to the track bus serving that area.  Lot easier to do that with stranded.

      Others prefer solid, one reason that made sense to me was they felt it was easier to strip the solid wire in order to connect a feeder.

>>>> At any rate solid is readily available to me. <<<<

      A bird in hand is worth two in the bus!

      Best regards,

      Steve

      Steve Haas

      Snoqualmie, WA

      Snow Birding for a few more days in  Mesa, AZ

dvollrath@...
 

I agree with what the goatfisher says. There is no significant difference between solid and stranded at the DCC frequencies of interest. the less flexible solid will tend to stay in place better and can strip easier for soldering on taps and is more readily available as already paired 12-14 awg, or larger. However, you can easily find 14-16 awg also in stranded and do pairing and twisting yourself. 2 conductor stranded  'zip' cord is also available but overpriced as 'speaker wire'.


DonV  



---In WiringForDCC@..., <Goatfisher2@...> wrote :

>>>>> Interesting that you say no difference between solid or stranded, I have read that stranded is not recommended for a power bus. <<<<<

>>>> At any rate solid is readily available to me. <<<<

john
 

Just two cents but:
Any time you run a pair of wires in parallel with a voltage on  them, they are more likely to affect other conductors, be affected by other conductors, and increase in capacitance. Twisting a pair diminishes this for the first two but not the third. All this is not likely yo affect track voltage but the wimpy control signal is at risk.
It is difficult to get an even twist on solid wires and it is difficult to manipulate 16, 14, and 12 gage wires.
It is easy to twist twisted conductors and they are easier to pull.
Finally, wire stripping is easily done with a plyer type stripper and most are adjustable or have multiple slots. My choice is a mechanical stripper. Mine can be used at an arms length in limited lighting just like under a layout. 
Hmmm, I am not sure that is worth two cents,
Thank you,
jd


On Wednesday, February 28, 2018 12:31 PM, "dvollrath@... [WiringForDCC]" wrote:




I agree with what the goatfisher says. There is no significant difference between solid and stranded at the DCC frequencies of interest. the less flexible solid will tend to stay in place better and can strip easier for soldering on taps and is more readily available as already paired 12-14 awg, or larger. However, you can easily find 14-16 awg also in stranded and do pairing and twisting yourself. 2 conductor stranded  'zip' cord is also available but overpriced as 'speaker wire'.

DonV  


---In WiringForDCC@..., wrote :

>>>>> Interesting that you say no difference between solid or stranded, I have read that stranded is not recommended for a power bus. <<<<<
>>>> At any rate solid is readily available to me. <<<<




dalemuir2@...
 

Here is an easy way to twist wire, especially 16, 14, and 12 gage house wire that you can buy at any home store:

 

You need a variable speed electric drill and a long work area such as a driveway.

 

1.       Unroll both wires in parallel across your work space.

2.       Fasten one end of both wires to a fixed object.

3.       Trim the free ends so both wires are the same length.

4.       Chuck the free end of both wires in your drill.

5.       Run the drill slowly until the wires are twisted to your satisfaction.

6.       The wires will untwist a little when released from the drill. That's OK, they are still twisted.

 

I've used this technique many times. It works great.

 

Dale Muir

 

From: WiringForDCC@... [mailto:WiringForDCC@...]
Sent: Wednesday, February 28, 2018 11:50 AM
To: WiringForDCC@...
Subject: Re: [WiringForDCC] Re: Bus Length

 

 

Just two cents but:

Any time you run a pair of wires in parallel with a voltage on  them, they are more likely to affect other conductors, be affected by other conductors, and increase in capacitance. Twisting a pair diminishes this for the first two but not the third. All this is not likely yo affect track voltage but the wimpy control signal is at risk.

It is difficult to get an even twist on solid wires and it is difficult to manipulate 16, 14, and 12 gage wires.

It is easy to twist twisted conductors and they are easier to pull.

Finally, wire stripping is easily done with a plyer type stripper and most are adjustable or have multiple slots. My choice is a mechanical stripper. Mine can be used at an arms length in limited lighting just like under a layout. 

Hmmm, I am not sure that is worth two cents,

Thank you,

jd

 

On Wednesday, February 28, 2018 12:31 PM, "dvollrath@... [WiringForDCC]" <WiringForDCC@...> wrote:

 

 

I agree with what the goatfisher says. There is no significant difference between solid and stranded at the DCC frequencies of interest. the less flexible solid will tend to stay in place better and can strip easier for soldering on taps and is more readily available as already paired 12-14 awg, or larger. However, you can easily find 14-16 awg also in stranded and do pairing and twisting yourself. 2 conductor stranded  'zip' cord is also available but overpriced as 'speaker wire'.

 

DonV  

>>>>> Interesting that you say no difference between solid or stranded, I have read that stranded is not recommended for a power bus. <<<<<

>>>> At any rate solid is readily available to me. <<<<

 

 

Ron Haviland
 

Just curious...how do you fish for goats? 

Steve Haas
 

>>>> Just curious...how do you fish for goats?  <<<<

 

Usually with a 12-foot eight weight fly rod with a weight forward floating line.  Maneuver your boat close to shore and use a roll cast to get the fly up the hill to the goat.  Needs custom tied flies that look like tufts of grass or other vegetation depending on locale and season.  Best locations are along the old GN line on the south side of Glacier Park, but they can be found elsewhere in the area.

 

Best regards,

 

Steve

 

Steve Haas

Snoqualmie, WA