Phil Euper <peuper@...>

Funny....I have looked at the DCC signal on my track with a scope
and the the output of my Command Station and they look
pretty much the same to my eye. Agree it is a complex signal
but seems to me we are just comparing real world scope
presentations here.

Regards

Phil Euper in SC

Sent: Friday, March 14, 2014 6:00 PM

,

Phil,

Wrong approach!

You probably missed my response to Ed as to why?

Like any piece of electronics being built testing has to start at a basic level to verify functions of the stages and progress to the final test. The command station signals are too complex for initial testing to verify good switching of the power H-bridge.

Re: Hot Snubber

redking56@...

Doc, your estimate of the length of the bus wires is pretty close, although my estimate is just under 200 feet.
My best estimate is 180 linear feet of bus wires.
Rich

Re: Hot Snubber

Doc Colin <colinseggie@...>

﻿
Hi Rich,
Please dont be offended by my previous post-- I really want your problem sorted-- I have my answers to the hot RC filter but I will let the experts chirp for now!
I am just loving the intelectual coversation and whole discussion going on here.
Can I say then, that from your diagram that, the whole loop of bus wire is in excess of two hundred feet ---that is going one direction from the  command station/booster all the way round and back to the command station/booster? [45+45+20+25+30+20+5+5+10 approximate from your diagram]
Doc Colin

----- Original Message -----
Sent: Saturday, March 15, 2014 11:33 AM
Subject: [WiringForDCC] Re: Hot Snubber

Let me throw another consideration into the mix.
Am I doing myself a disservice by even having snubbers on my bus wires?
Rich

Re: Hot Snubber

redking56@...

Let me throw another consideration into the mix.
Am I doing myself a disservice by even having snubbers on my bus wires?
Rich

Re: Hot Snubber

redking56@...

Ahh, the new morning brought success.  I was able to post a crude diagram of my bus wiring in the Photos section.  It is not to scale.  As you view the diagram, the actual layout is 42' vertically and 25' horizontally.

The black line traces the bus wires which run below my double mainline.  This is what I refer to as a "continuous loop".  The circles represent the approximate location of the snubbers.  The ones colored blue are cool or warm to the touch.  The one colored red is hot to the touch.

For perspective, I show the location of my command station and booster.

Does this help?

Rich

Re: Hot Snubber

colinseggie@...

Guys this is still a gripping episode of " Wiring for DCC!"
A wealth of information beeing set out in laymans , dare I say layrailroaders engineers language. I have a very simple DCC track-- a six foot oval with a five foot  inside oval and branch line inside that. Three turn outs in total and its on a 4X6 board on the the top bunk of my Grandsons bed-- so easy to change things around and experiment with wiring:--- its my exerimental track whilst I design my "REAL" railroad, and my grandsons "Thomas Track" over the weekends.
Its set up in "Best Practices Mode using the Zephyr Xtra" everything is done according to Alan G or Mark G.
There's one insula and one electro  frog 'peco' turnout, and a "horby point"
During the week I'm busy & all works well, over the weekend Finlay "Penske" ( forgive my age) is here and Thomas Screems around (thro' closed tounouts) into the engine shed like "Robin Williams" drives, and the shed mooves a foot as all come to a stop. etc etc. The screen on the Zephyr Xtra looks like the old packman screen ( mulpiple 000's racing across.) We shut down, turn on, and race around again no problems as easy as that.
But before I joined any group 4 years ago I set up the same track My and my model shop owners way.
The only difference was a Zephyr and not the ZephyrXtra, and the kid next door who just happened to be nick named Dennis!     Main Bus-(You Have to take my work on this) Two continuous oval buses, one had a feeder.
No RC filters    .2 feeders to the entire track because the the shop owner said one pair every 6 feet. We  ( I ) had endlees problems, shut down after shut down --Dennis I actually think less than me. After a shutdown we had to wait 60 secs before we cold power up again.I went through a decoder a month etc etc. Hence joining the groups and listening to you guru's.
Forgive me I'm old and long winded, but have been to the silver haired University!! Bottom line- there's always two ways to do things-- evidence based rairoading which changes with time- or listen to quasi-experts with crystalised minds intime. Both work but one ALWAYS superceeds the other.
Rich---
Please DONT use best practices and gap the bus--keep getting and touching that hot snubber, and above all  continue to call it a snubber. Cause I have never learnt So Much, from So Many, in such a Short Time!!
Doc Colin

Re: Hot Snubber

Flash Gordon

More wood for the fire.

This from The Atlas forum  2011:

Quote:

"posted - 2011 February 07 :  8:15:05 PM

Hello;

My system is a Power Cab so who better to ask then those that made it?

This afternoon I called NCE Tech Support regarding the continuous loop.

I was told that some DCC systems use components that cause problems with continuous loops.

And, that NCE does not use those components and any NCE system will work with a continuous loop.

thanks,

nicholas"

Unquote:

Ed S

At 08:35 PM 3/14/2014, you wrote:

Now, I read from time to time that a continuous loop for the bus wires is allegedly a no-no.  Yet, when I express concern, the response is not to worry if I don't have problems.  So, I don't know if the continuous loop i is bad or not.  What is the problem with it.

Rich

Re: Hot Snubber

Vollrath, Don <dvollrath@...>

In a nutshell, Charlie, the answer is yes. DCC voltage power to the track alternates quickly between + and – polarity. During each cycle the voltage on the capacitor changes from zero to +14 V, then to zero, then to -14 V, then to zero, and then the cycle starts over again. Current must flow in-to and out-of, or essentially through, the capacitor and resistor to charge and discharge it to those voltages. The small amount of energy that flows on each transition is ½ x C x V^2. The charge and discharge current of the capacitor obviously flows through the resistor which limits the magnitude of peak amps, but not the total flow of energy. However with DCC, the voltage transitions occur 4 times total per DCC polarity cycle, which occurs roughly 8,000 times per second. The net result is that the resistor sees 4 x ½ x C x V^2 x 8000 = Resistor watts, when C is in Farads and V is in volts. With V=14 volts and C=0.1 microFarad the net result is that the resistor will see 0.31 watts. (regardless of the value of the resistor if it is about 100 ohms).

DonV

From: WiringForDCC@... [mailto:WiringForDCC@...] On Behalf Of Charlie Sleep
Sent: Friday, March 14, 2014 2:50 PM
To: WiringForDCC@...
Subject: RE: [WiringForDCC] Re: Hot Snubber

﻿

I am the last person to ask regarding anything electronic. Having said that, it seems to me that a resistor would have to be conducting current to get warm and a capacitor is supposed to block DC current. Is the snubber actually passing enough AC through the network to produce current fluctuations strong enough to heat the resistor?

Thanks for clarifying my ignorance.

Charlie Sleep

Re: Hot Snubber

Flash Gordon

Rich,

I saw your question about why not to use a continuous loop in DCC.  I am building a large layout and I am using Allan Gartner’s web site as my bible:

http://www.wiringfordcc.com/track.htm

His instructions recommend not to using a continuous loop but he does not give a reason. So I started a search and found this idea has been argued since the beginning of DCC.

One comment suggested that Allan leans toward problems in large layouts and I believe he tends to lean toward suggestions that will cause the least problems. I agree with that. DCC can get so complicated that if you have a problem later it may be very difficult to solve if you do not follow some sort of standard.

So what is the bottom line?  The following post I found On Bachmann’s train site and I think it sums it up.

http://www.bachmanntrains.com/home-usa/board/index.php?topic=18954.0;wap2

I am not an electrical engineer but stayed at a Holiday Inn Express once…..

I post the following so the engineers can pick it apart.

I quote:

“Jim Banner:
Both Doneldon and Mabloodhound are correct, depending on the size and shape of the layout.  You can run continuous loops on small layouts; say 1 to 2 sheets of plywood in size.  But large layouts, particularly around the wall types that enclose a large area, can resonate at harmonics of the DCC frequencies, causing large voltage spikes that can interfere with decoders or even damage them.

The DCC buses and the tracks form large coils while the capacitance between the rails and the wires form a distributed capacitance in parallel with the coils.

Capacitors and coils in parallel form tuned circuits.  If the capacitors and coils are small, as on a small layout, the resonant frequency is high, so high in fact that the harmonics of the DCC fundamental frequency are virtually nonexistent.  As the coils grow larger and the capacitance across them increases, the resonant frequency drops.  When the harmonics are powerful enough and the frequency resonates with the DCC wiring, the large spikes mentioned above occur.

The first sign of problems is usually loss of control at points far away from the command station or booster.  Some decoders are more sensitive than others to the voltage spikes and usually lose control first.

Jim “

Unquote….  I think the last paragraph fits my thinking about eliminating potential problems.

Your new layout sounds like it is getting complex. You may want to take some time and read Allan’s website for more insight.

Ed S

At 08:35 PM 3/14/2014, you wrote:

Now, I read from time to time that a continuous loop for the bus wires is allegedly a no-no.  Yet, when I express concern, the response is not to worry if I don't have problems.  So, I don't know if the continuous loop i is bad or not.  What is the problem with it.

Rich

Re: Hot Snubber

Flash Gordon

Rich,

And I will send something to your email.

Ed S

Re: Hot Snubber

Flash Gordon

Rich,

It is not working. I tried to add a photo to your album and then to my album. It did not work, it just hangs up.

Ed S

At 11:13 PM 3/14/2014, you wrote:

Hang on rich I will try to post a photo.

Ed S

At 11:09 PM 3/14/2014, you wrote:

Is there a problem tonight with the Photos section?
Rich

Re: Hot Snubber

Flash Gordon

Hang on rich I will try to post a photo.

Ed S

At 11:09 PM 3/14/2014, you wrote:

Is there a problem tonight with the Photos section?
Rich

Re: Hot Snubber

redking56@...

Is there a problem tonight with the Photos section?
Rich

Re: Hot Snubber

Bob <rehandjr@...>

Rich,

Guess we missed the continuous loop statement.  Changes everything (like mio), lol).  Split the bus halfway to the left of the booster and half way to the right.  Snubb at the two ends that were split.  The snubbers will be sitting right beside each other!!  What happens then?bob

From: WiringForDCC@... [mailto:WiringForDCC@...] On Behalf Of redking56@...
Sent: Friday, March 14, 2014 9:52 PM
To: WiringForDCC@...
Subject: Re: [WiringForDCC] Re: Hot Snubber

I just put together a crude diagram of my bus wiring, showing the location of the snubbers.

But, I have tried twice to post it, but it seems to be hanging up.
As soon as I can post it, I will let everyone know.
Rich

NOTE: This message was trained as non-spam. If this is wrong, please correct the training as soon as possible.
Spam
Not spam
Forget previous vote

Re: Hot Snubber

redking56@...

I just put together a crude diagram of my bus wiring, showing the location of the snubbers.
But, I have tried twice to post it, but it seems to be hanging up.
As soon as I can post it, I will let everyone know.
Rich

Re: Hot Snubber

Flash Gordon

Rich,

We are from different parts of the country even different parts of the world. For some English may not be their first language. So semantics can be a problem. You saw that at least two folks read your post differently.

Your post was fine; it just can be interpreted different ways. I agree with Len, drawings would be very helpful.

Ed S

At 08:20 PM 3/14/2014, you wrote:

I love this forum, but sometimes you guys can be a tough crowd.
I thought that my explanation was pretty clear, one booster, no separate power districts or circuit breakers, bus wires form a continuous loop. But, I will try harder in the future to be as clear as possible.
Rich

This is where actual wiring diagrams are a plus as opposed to verbal explanations. With the verbal, we can only visualize and the error in interpretation amplify. So yahoo doesn't allow attachments.

My suggestion is to respond to the sender/senders where an attachment is possible. This would lead to a possible solution.

Otherwise everyone is only speculating that only leads to bringing the problem further out of the ballpark and away from a solution.

Ranting again!

Re: Hot Snubber

Flash Gordon

The group owner can set the group so attachments can be posted. I moderate a group with that feature and it sure makes things easier.

Ed S

At 08:08 PM 3/14/2014, you wrote:

This is where actual wiring diagrams are a plus as opposed to verbal explanations. With the verbal, we can only visualize and the error in interpretation amplify. So yahoo doesn't allow attachments.

My suggestion is to respond to the sender/senders where an attachment is possible. This would lead to a possible solution.

Otherwise everyone is only speculating that only leads to bringing the problem further out of the ballpark and away from a solution.

Ranting again!

Re: Hot Snubber

jazzmanlj

Hey Rich,

Post,send a exact diagram of your layout wiring and what you refer to as continious loop. The verbal is misleading everyone so the answers are ???

Re: Hot Snubber

redking56@...

Oh boy, can I plead the 5th Amendment here?

OK, here is my story.  Back in 2004, when I was a rank newcomer to HO scale, I converted a 12'x 8' layout to DCC, having purchased an NCE PH-Pro 5 amp system.  Not knowing any better, I formed my bus wires in a continuous loop.  Later, I expanded my layout quite extensively.  At that time, I cut the bus wires and joined them to newly installed bus wires, using plastic wire nuts to join the wires.  But the bus wires still formed a continuous loop.  I further expanded my layout a few years ago, once again joining the new bus wires to the old wires, using plastic wire nuts to join the wires.  Again, the bus wires formed a continuous loop.

Then, I read on this forum about snubbers.  I inquired about their placement on my layout and was advised to place one near to where the bus wires were joined together.  Today, I have six snubbers as a result.

Now, I read from time to time that a continuous loop for the bus wires is allegedly a no-no.  Yet, when I express concern, the response is not to worry if I don't have problems.  So, I don't know if the continuous loop i is bad or not.  What is the problem with it.

Incidentally, I am about to create four power districts on my layout and protect each district with a circuit breaker.  In preparation for this move, I had considered dividing the layout in two and adding a second booster. But, it has been suggested to me that I stay with one booster but run a new set of bus wires from the midway point in my bus wire loop back to the command station, effectively dividing the bus into two sections.  I plan to do that.

So, there is my story.  Waddya think?

Rich

Re: Hot Snubber

jazzmanlj

Skip,

Measuring voltage drops will not tell anything.  Even though the base frequency is about 8kHz, ringing voltages are far beyond that and the response time of the meter is way too slow. My 20MHz Omron scope is not even good enough to capture a good waveform.

There are some interesting PC based scopes available for under \$200 with bandwidth to 200MHz. Reasonable investment for the serious guy!