Terminating busses

Earl T. Hackett

Well, I managed to answer most of my questions pretty quickly once I
looked up the specification for the booster wiring.

The boosters can be placed at any distance from the command station so:

- The heavy distribution busses are gone as of about 15 minutes ago.
- The boosters will be moved to the various power distribution panels
and will be used to power all track in that general area - EB, WB, or
yard.
- A 4th booster will be purchased and used for the staging tracks
which are located in another room.
- Since I've only rewired only a couple of blocks, they'll be pulled
out, the bus wires twisted, and an RC filter placed at the end.

Twisting the pairs also helps find the wire pair supplying the block
if I ever need to track them down again.

Any problem with the above changes??

It seems that we should be describing the number of boosters required
based on the length of the power runs rather than on the amperage
required to drive the anticipated power requirements of the operating
locomotives.

wirefordcc

#420

Earl,

We have two people who have a lot of experience with twisting buses 
and terminations.  I suspect they are both on vacation this week.  If
they are not too swamped when they get back, maybe you will hear from
them next week.

You have done what I have done - located my boosters near the district
they power.

While you could figure booster need based on wiring length, I don't
think you need to do so in most cases.  Twisting and adding
terminations allow you to go greater distances.  Even if you hold to
30' maximum, if you put the booster in the middle of a district, that
means that district can be 60' long.  That suits most people.

Allan

Earl T. Hackett

#421

Show quoted text

----- Original Message ----- 
  From: wirefordcc 
  To: WiringForDCC@... 
  Sent: Friday, December 30, 2005 11:03 AM
  Subject: [WiringForDCC] Re: Terminating busses

  Earl,

  You have done what I have done - located my boosters near the district 
  they power.

Actually I hadn't, but it's going to happen as part of this rewiring project.  My only concern is with 50 or so lines going out to various blocks, all those termination caps could over compensate the signal.  I only have a 20 MHz analog scope and I don't know if it's up to looking at such detail.

wirefordcc

#426

Earl,

Your 20 MHz scope should be more than adequate do the job for you.

You say you have 50 blocks, but how many on each booster?  How many
are over 30' feet away?  If you had to put 50 terminations all hanging
off of one booster, they would represent a significant load on your
booster.  But I doubt your situation is as serious as this.

Since you have a scope, and I presume you have a basic operating
knowledge of it, you will be able to figure out exactly what you need.

Hopefully Mark and Don will be back next week and offer their advice.

Allan

Earl T. Hackett

#430

Right now there are 3 boosters and I'm planning on adding a fourth for the storage tracks in the other room.  One booster has 18 blocks, but several are very small yard ladders or just two point to point turnouts.  

When I was starting this layout I was considering whether I should switch to DCC.  The ability to have an independently controlled helper on the grade was the deciding factor.  Although I was concerned with signal distortion, I could find no one that understood what I was talking about - or if they did, they weren't talking.  Everyone said to just substitute a booster for a DC  powerpack, add decoders, and everything will work just fine.  The only concern tabled was the amperage capacity of the boosters and the potential for resistance heating in case of a derailment.  I suspect that there was a desire by many individuals to see the DCC system succeed and no one was going to say anything bad about it.  So with old DC wiring as a guide, I wired a booster to the EB and WB main with another for the yards.  The double track main is about 400' long.  From your website, it is obvious that my original concerns were well based and DCC is not suitable for use on long runs without special considerations.  

With the rewiring, boosters are all being moved to the power distribution panels so the longest transmission distance will be about 25'.  This rewiring project is expected to take at least 3 months.  I really like the twisted pair arrangement as it helps keep things organized.  Right now I'm just wiring the track to toggle switch cutoffs to aid in troubleshooting and leaving a small length of wire to which a compensating RC circuit can be added.  Once that is done there is a cross over and a couple of turnouts that have to be added to the mainline to allow the proper switching moves at White Sulfur Springs.  It will be at least 5 months before I'm ready to fire up the power and turn a wheel so there's plenty of time to figure out what is really required.

Mark Gurries

#443

Right now there are 3 boosters and I'm planning on adding a fourth forthe storage tracks in the other room.  One booster has 18 blocks, but
several are very small yard ladders or just two point to
point turnouts.

When I was starting this layout I was considering whether I shouldswitch to DCC.  The ability to have an independently controlled helper
on the grade was the deciding factor.  Although I was concerned with
signal distortion, I could find no one that understood what I was
talking about - or  if they did, they weren't talking.  Everyone said to
just substitute a booster for a DC  powerpack, add decoders, and
everything will work just fine.

Both, you and your responses from others are correct.  Two thoughts.

1) Given that by far most layouts are small bedroom or small two car
garages size, DCC is not that sensitive.  The DCC signal from the very
beginning was understood to be passing through wiring that was less than
optimal for low distortion clean tranmission of essentially a digital
pulse signal.

2) By far again most model railroaders are NOT Electrically inclined to
understand these technical issues related to digital transmission lines.
There concept of electricity is limited to two kinds.  120VAC for the
house and 12VDC for the layout.

Thus by definition, the protocol and electrical requirements such as
rise time and frequency rates were kept relatively low such that success
would be maximized for the typical the users.  In other words, no
specialized electrical wiring or knowledge will required to achieve
success.  Stated yet on other way again.  All technical aspects of DCC
should be simplified or eliminated such that people FEARS of the "DCC
System" are minimized.  Let DCC be seen as being just as simple as DC as
much as possible.

That is exactly what has been achieved and thus that is why you get
blank stares and confusing responses from individuals.  Frankly they
have no idea what you talking about and that is EXACTLY the what DCC
industry wants.

But the DCC system has limits and can be broken with large layouts.  So
you concern is also valid.

The only concern tabled was the amperage capacity
of the boostersThat absolute number depends on the total number of engines (motor)
running at one time and the total current they will draw.  Typically if
you use 0.6A for each HO engine, you can figure out how many amps you
need. Typically with modern motors, the current is less than 0.5A.  In
practice, 5A can run a lot of trains if they do not all have sound.
Sound locos have very high peak current demands but the power draw is
very low.  Since booster only look at current versus time as the
deciding factor in when to shutdown the booster, to many sound unit can
reduce the effective running locomotive count.

and the potential for resistance heating in case of a derailment.Your concern is correct. 14V (HO) @ 5A = 70 Watts....more than enough
power to solder and burn things with.

A popular minimum standard for DCC wiring acceptability is the "quarter
test".  The quarter refers to the ability of the US quarter shot short
both rails together.  The procedure is to short each section of layout
track between rail joiners to make sure the booster sees the short and
shuts down.  If a section fails, the track and/or wiring needs to be
adjusted or fixed to pass the test.

This level or performance at least addresses the layout wiring and track
resistance to be low enough to permit the booster to offer some
protection on a short circuit and shutdown.

Higher levels of wire performance address:

1) Voltage losses related to wire resistance .  This is a wire gauge
versus length goal.  Pick a maximum voltage drop at 5A you want and from
there you can calculate the required wire resistance.  IF you know the
distance the cable will run, then you can figure out the wire gauge
needed to get that desired resistance at the distance.  Remember that
the wire is out and back.  So 50FT of wire is a 25Ft run.  There is some
information on that on the website too.

2) Inductive induced voltage losses (wire length) issues.  This is new
loss factor because of the true nature of the DCC signal...it is a form
of AC and not DC.  Think impedance as opposed to pure DC Resistance. The
solution is twisting the supply and return wire together as in "twisted
pair" just like they do in high speed datacomm cables.  Only here you
twist (very slowly) the large gauge stranded wires into pair using a
drill to about 3 twist per foot or better.  oh...use a color code too...


I suspect that there was a desire by many individuals to see the DCCsystem succeed and no one was going to say anything bad about it.  So
with old DC wiring as a guide,

That would be the correct thing to do as a starting point.

I wired a booster to the EB and WB main with anothers for the yards.Excellent power partitioning plan.  A better more cost effective
solution would be to use Electronic Circuit breakers (CB) with a single
booster.  It would be cheaper to use a 10Amp booster with a quad CB set
to 5Amps each.  That would give you four 5 amp power districts.
Granted you only have 10A of booster power...but I be surprised you even
get close to 5A.  It no different than your house CB panel.  The main it
less than the combined total of all the smaller CB it feeds!

The double track main is about 400' long.  From your website, it is
obvious that my original concerns were well based and DCC is notsuitable for use on long runs without special considerations.

400 feet long, but how it laid out....multiple level over each other?

With the rewiring, boosters are all being moved to the powerdistribution panels so the longest
transmission distance will be about 25'.  This rewiring project isexpected to take at least 3 months.  I really like the twisted pair
arrangement as it helps keep things organized.

Excellent...you seem to be on top of everything...You appear to not need
our help after all!

Right now I'm just wiring the track to toggle switch cutoffs to aid introubleshooting and leaving a small length of wire to which a
compensating RC circuit can be added.  Once that is done there is a
cross over and a couple of turnouts that have to be added to the
mainline to allow the proper switching moves at White Sulfur Springs.
It will be at least 5 months before I'm ready to fire up the power and
turn a wheel so there's plenty of time to figure out what is really
required.

Oh...in terms of total number of terminators..only one needed for each
primary stub run in a given power district.  A stub being a feed that
starts at the booster or CB location and move out.  The RC terminator is
installed at the opposite end at the farthest wire run end of the entire
stub.  Branches the take off of the main stub often do not need RC
filters.  But if a branch is longer than the stub...then your definition
of the end of the main stub is incorrect.

Hope this helps.

Best Regards,

Mark Gurries
Linear Technology
Power Supply & Battery Charger Applications Engineer/Manager
---------------------------------------------------------
Model Railroad Club and NMRA DCC presentations are at:

--------------------------------------------------------
Audio Enthusiast (Love SAE equipment)

----------------------------------------------------------

Earl T. Hackett

#444

OK Mark.  This one is going into a folder so I can read it a couple of times.  The 400' main is really 400'.  It was broken into signaling sections, each with its own feed to one rail so I could utilize current sensing detectors.  So I really don't have to replace all the distribution wiring, just half of it.

Things are going reasonably well.  I can rewire a block in about a day's time.  With 50 blocks I should be done by summer......

Show quoted text

----- Original Message ----- 
  From: Mark Gurries 
  To: WiringForDCC@... 
  Sent: Tuesday, January 03, 2006 7:51 PM
  Subject: Re: [WiringForDCC] Re: Terminating busses

Vollrath, Don

#445

Some really good Q & A info here folks!
DCC can be and is simple for most small layouts and users.

It is the larger layouts and 'simplified' sales and application info that stretch the technical design issues beyond practical limits that cause all the fuss.  Specific improvements, like using twisted pair wiring, terminated busses and electronic CBs help to make DCC work well even on large layouts.  The enemies of good DCC operation are poor (unsoldered or lose) electrical connections, unexpected short circuits (particularly on older turnout designs & oversized wheel sets) and loss of adequate voltage or signaling due to AC transmission line effects in old fashioned type DC wiring ('cured' or at least extended working limits by use of twisted pairs & r/c terminations).

Helping others across the education barrier from RR hobby novice to understanding the electrical How-To issues without destroying interest or breaking your pocketbook is what this (and other) forums are all about.

DonV

Show quoted text

-----Original Message-----
From: WiringForDCC@...
[mailto:WiringForDCC@...]On Behalf Of Mark Gurries
Sent: Tuesday, January 03, 2006 6:51 PM
To: WiringForDCC@...
Subject: Re: [WiringForDCC] Re: Terminating busses

Right now there are 3 boosters and I'm planning on adding a fourth forthe storage tracks in the other room.  One booster has 18 blocks, but
several are very small yard ladders or just two point to
point turnouts.

When I was starting this layout I was considering whether I shouldswitch to DCC.  The ability to have an independently controlled helper
on the grade was the deciding factor.  Although I was concerned with
signal distortion, I could find no one that understood what I was
talking about - or  if they did, they weren't talking.  Everyone said to
just substitute a booster for a DC  powerpack, add decoders, and
everything will work just fine.

Both, you and your responses from others are correct.  Two thoughts.

1) Given that by far most layouts are small bedroom or small two car
garages size, DCC is not that sensitive.  The DCC signal from the very
beginning was understood to be passing through wiring that was less than
optimal for low distortion clean tranmission of essentially a digital
pulse signal.

2) By far again most model railroaders are NOT Electrically inclined to
understand these technical issues related to digital transmission lines.
There concept of electricity is limited to two kinds.  120VAC for the
house and 12VDC for the layout.

Thus by definition, the protocol and electrical requirements such as
rise time and frequency rates were kept relatively low such that success
would be maximized for the typical the users.  In other words, no
specialized electrical wiring or knowledge will required to achieve
success.  Stated yet on other way again.  All technical aspects of DCC
should be simplified or eliminated such that people FEARS of the "DCC
System" are minimized.  Let DCC be seen as being just as simple as DC as
much as possible.

That is exactly what has been achieved and thus that is why you get
blank stares and confusing responses from individuals.  Frankly they
have no idea what you talking about and that is EXACTLY the what DCC
industry wants.

But the DCC system has limits and can be broken with large layouts.  So
you concern is also valid.

The only concern tabled was the amperage capacity
of the boostersThat absolute number depends on the total number of engines (motor)
running at one time and the total current they will draw.  Typically if
you use 0.6A for each HO engine, you can figure out how many amps you
need. Typically with modern motors, the current is less than 0.5A.  In
practice, 5A can run a lot of trains if they do not all have sound.
Sound locos have very high peak current demands but the power draw is
very low.  Since booster only look at current versus time as the
deciding factor in when to shutdown the booster, to many sound unit can
reduce the effective running locomotive count.

and the potential for resistance heating in case of a derailment.Your concern is correct. 14V (HO) @ 5A = 70 Watts....more than enough
power to solder and burn things with.

A popular minimum standard for DCC wiring acceptability is the "quarter
test".  The quarter refers to the ability of the US quarter shot short
both rails together.  The procedure is to short each section of layout
track between rail joiners to make sure the booster sees the short and
shuts down.  If a section fails, the track and/or wiring needs to be
adjusted or fixed to pass the test.

This level or performance at least addresses the layout wiring and track
resistance to be low enough to permit the booster to offer some
protection on a short circuit and shutdown.

Higher levels of wire performance address:

1) Voltage losses related to wire resistance .  This is a wire gauge
versus length goal.  Pick a maximum voltage drop at 5A you want and from
there you can calculate the required wire resistance.  IF you know the
distance the cable will run, then you can figure out the wire gauge
needed to get that desired resistance at the distance.  Remember that
the wire is out and back.  So 50FT of wire is a 25Ft run.  There is some
information on that on the website too.

2) Inductive induced voltage losses (wire length) issues.  This is new
loss factor because of the true nature of the DCC signal...it is a form
of AC and not DC.  Think impedance as opposed to pure DC Resistance. The
solution is twisting the supply and return wire together as in "twisted
pair" just like they do in high speed datacomm cables.  Only here you
twist (very slowly) the large gauge stranded wires into pair using a
drill to about 3 twist per foot or better.  oh...use a color code too...

I suspect that there was a desire by many individuals to see the DCCsystem succeed and no one was going to say anything bad about it.  So
with old DC wiring as a guide,

That would be the correct thing to do as a starting point.

I wired a booster to the EB and WB main with anothers for the yards.Excellent power partitioning plan.  A better more cost effective
solution would be to use Electronic Circuit breakers (CB) with a single
booster.  It would be cheaper to use a 10Amp booster with a quad CB set
to 5Amps each.  That would give you four 5 amp power districts.
Granted you only have 10A of booster power...but I be surprised you even
get close to 5A.  It no different than your house CB panel.  The main it
less than the combined total of all the smaller CB it feeds!

The double track main is about 400' long.  From your website, it is
obvious that my original concerns were well based and DCC is notsuitable for use on long runs without special considerations.

400 feet long, but how it laid out....multiple level over each other?

With the rewiring, boosters are all being moved to the powerdistribution panels so the longest
transmission distance will be about 25'.  This rewiring project isexpected to take at least 3 months.  I really like the twisted pair
arrangement as it helps keep things organized.

Excellent...you seem to be on top of everything...You appear to not need
our help after all!

Right now I'm just wiring the track to toggle switch cutoffs to aid introubleshooting and leaving a small length of wire to which a
compensating RC circuit can be added.  Once that is done there is a
cross over and a couple of turnouts that have to be added to the
mainline to allow the proper switching moves at White Sulfur Springs.
It will be at least 5 months before I'm ready to fire up the power and
turn a wheel so there's plenty of time to figure out what is really
required.

Oh...in terms of total number of terminators..only one needed for each
primary stub run in a given power district.  A stub being a feed that
starts at the booster or CB location and move out.  The RC terminator is
installed at the opposite end at the farthest wire run end of the entire
stub.  Branches the take off of the main stub often do not need RC
filters.  But if a branch is longer than the stub...then your definition
of the end of the main stub is incorrect.

Hope this helps.

Best Regards,

Mark Gurries
Linear Technology
Power Supply & Battery Charger Applications Engineer/Manager
---------------------------------------------------------
Model Railroad Club and NMRA DCC presentations are at:

--------------------------------------------------------
Audio Enthusiast (Love SAE equipment)

----------------------------------------------------------

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Terminating busses