Date   

Re: RC Snubber question

asychis@...
 

Thanks for all the feedback about snubbers.  We're kind of getting to the question I had. I was a bit unclear I suppose.  I was wanting to know what the manifestations are, i.e. what do you see on the layout if you need snubbers or if you have a missing or lose signal ground.  I understand the voltage and amps measurements  and have built the circuits Allen shows in his documents.  In fact, I have printed off and bound "Wiring for DCC" and use  as a bible. What I was looking for is something along the line of:
 
If you have a missing signal ground your locomotives will.....
 
You may need a snubber if your locomotives ....
More to explain to my fellow club members.
 
Jerry Michels


Re: RC Snubber question

Vollrath, Don <dvollrath@...>
 

Ed,

You need to read Mark’s website stuff again. There are just too many variables to support your all inclusive statement of ‘no matter how large’.

 

The real problem of voltage ‘spiking’ starts with the inductance of your wiring, which will never be zero. This is related to the length of wiring run no matter how it is constructed. [Yes, twisted pair wiring does help.] The second part is the ability of your booster to provide instantaneous amperes into an unwanted short circuit out on your layout. [This is not the same as the so called product ampere rating.] The third part is what happens when that track short becomes interrupted (because the loco wheels are still moving) and the sensitivity of any given decoder to absorb the short circuit energy stored in the inductance of the wiring. That energy will be ½ x L x i^2 where the current, i, is the instantaneous current that was flowing into the short circuit… before the booster (or electronic CB) trips. [this can easily be 3-5 times the rating of your booster, or more, depending on brand and how it is constructed.] As the short circuit becomes broken that energy must and will go somewhere… either into a voltage spike (the L x di/dt part) causing a spark, or be absorbed into an R/C filter, or into a nearby DCC decoder where it may be simply absorbed by filtering internal to the decoder, or somehow cause damage in the form of CV memory corruption or actual physical voltage breakdown destruction to the decoder. [Evidence tells us that some decoders are less robust and more susceptible to damage than others.]

 

Use the basic principles of the best practices guidelines. If you have long DCC bus runs, add R/C snubber/filters. How long is too long? Evidence indicates that problems seem to start at 30+ ft (>9 meters) from the booster. Your luck may vary.

 

DonV… the guy who took the scope pictures on his home layout and posted them on wiringfordcc.com.  

 

From: WiringForDCC@... [mailto:WiringForDCC@...]
Sent: Monday, August 11, 2014 7:17 AM
To: WiringForDCC@...
Subject: Re: [WiringForDCC] RC Snubber question

 



Mark,

Great response and web post.  It appears that you are saying that IF I construct my layout with proper wiring (twisted pairs and solid connections) I do not have to worry about RC filters at all no matter how large my layout is - is this correct?

Ed Robinson



Re: RC Snubber question

Ed
 

Mark,

Great response and web post.  It appears that you are saying that IF I construct my layout with proper wiring (twisted pairs and solid connections) I do not have to worry about RC filters at all no matter how large my layout is - is this correct?

Ed Robinson


LocoHub4 or LocoHub8

asychis@...
 

Hi, is anyone using these neat-looking Loconet multiple connectors?  On the website I only see Conrad numbers for the sockets.  Does anyone know a Mouser or Allied number?
 
Thanks,
 
Jerry Michels


Re: RC Snubber question

Mark Gurries
 

I have updated my website with more of the why’s and how of a RC Filter applications and installation.


I also included a link to WHY I call it a RC filter as opposed to a snubber or terminator.


Still have more work to do with this section when I get some more free time.

Best Regards,

Mark Gurries
Electrical Engineer
DCC Website & NMRA DCC Clinics: www.markgurries.com




Re: RC Snubber question

Douglas Krahn
 

Jerry:

 

About the best source of information on DCC signals is http://www.wiringfordcc.com/dcc_waveforms.htm.  First let me say without an oscilloscope its hard to understand the problem.  The site listed shows what happens to high speed switching signals.  There are a couple ways to help reduce the “sign spike,” one being snubbers another is twisting the signal cable (in this case the cable providing power to the track.  Another is to keep the signal cable as short as possible. Again the signal cable is the power cable going to the track.  If you look at the signal on Allan Gartner’s site you will see that adding a snubber reduces the peak to peak ringing; however, the leading edge of the signal is somewhat rounded off.  Add too many snubbers and you loose the leading edge completely.

 

What to look for if you think you are having problems is loosing control of loc’s and blowing decoders (again looking at the peak to peak voltage of the site).  The voltage can be higher than what the decoder is designed for.  I have seen at least 4 decoders blown when we had rather large layouts and long cable runs. At the time we couldn’t figure out the problem, but did not have an o’scope available

 

Another thing one should understand is that a DCC signal is NOT the same as a DC signal.  A DC signal is referenced to ground.  The voltage on the track is positive or negative voltage in reference to ground.  A DCC signal is NOT reference to ground in any way.  It is a Peak to Peak signal, Not connected to ground in anyway.  If you connect your DCC signal to ground YOU WILL DAMAGE something.  You do want to connect all chassis together so they are at the same potential to help ensure someone doesn’t get shocked (not all ground is the same).

 

This signal problem is not with just DCC units, but with any high speed switching, such as computer and computer cabling.

 

I hope this has belped and not added to the confusion.  I have been in computers all the live and still have problems.  And even a harder problem describing the problem

 

Doug


Re: RC Snubber question

wirefordcc
 

It seems that Yahoo has "improved" the Groups.  I tried pasting links to the RC terminator and information on long bus runs.  The new improvements provide an unrelated graphic.


Until I figure out how to get it to leave well enough alone, paste the following two links into your browser and you will get the information on the RC terminators.


Scopes are great, but I expect that most modelers won't buy one.  Even so, once you buy one, you need to know how to use it.  So it might be a good idea to find someone who already has one and knows how to use it.  If you think a scope might be for you, get one.  They really are a great tool.


The one caution I have is that RC terminators are not a cure all for all problems.  If you find yourself sprinkling them everywhere and using several of them in one spot, you probably are using the wrong solution for your problem.


Allan Gartner

Wiring For DCC


http://www.wiringfordcc.com/track_2.htm#a47

 

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



Re: RC Snubber question

jazzmanlj
 

Go to Alan's website first and search the subject. There you can find lots of information, diagrams and waveforms explaining the need for snubbers. An oscilloscope is a great tool for diagnosing problem areas but out of reach for most modelers. There is a decent USB unit from Virtin for about $150 on Ebay. I've got a 20MHz scope but not good enough so I'll spring for the Virtin.

Len Jaskiewicz


Re: RC Snubber question

asychis@...
 

"No need for a snubber near the command station as it's built in. Putting in more is a an open discussion. In some instances it causes problems instead of fixing them."
 
What sort of problems?  I have read this, but don't know what to look for. Could someone give a description of the problems you have with or without snubbers, and also what are the manifestations of not have the system properly chassis/case/signal grounded?  Thanks!
 
Jerry Michels


Re: RC Snubber question

jazzmanlj
 

Glad to see all are satisfied by the questions. Also glad to see the terminology proper! A 'snubber' is meant to suppress and subdue unruly voltage spikes to a safe level for the system involved. A 'filter' implies small signal noise! I won't get into any further discussions as to the proper terminology.

Regards to all,

Len Jaskiewicz


Re: RC Snubber question

esimard
 

Thanks Mark

Exact answer I was looking for.  BTW no block detection so that's not an issue.
_Ernie


Re: RC Snubber question

jazzmanlj
 

Mark,

Perhaps my wording wasn't correct. Placement is important and so many pitfalls/problems in  the wrong locations. I think good diagrams should be posted as to the good vs. problematic placement. This would be a benefit.

Regards,

Len Jaskiewicz


Re: RC Snubber question

Mark Gurries
 

On Aug 8, 2014, at 4:36 PM, len.jask@... [WiringForDCC] <WiringForDCC@...> wrote:

Putting  in more is a an open discussion. In some instances it causes problems instead of fixing them. 

Why did you say that?  I never said that and there is not a single example of this being true.  I have always stated the opposite.  Put in as many as you need where you need them IF you need them.

Start with ONE RC filter per bus if you have a track bus longer than 30Ft and place it at the far end of the track bus furthest point relative to the booster.   

One should only consider adding more RC Filters if there have been any problems observed and if that happens, place another RC filter AT THAT LOCATION.  There are no rules saying were you cannot put one.

Best Regards,

Mark Gurries
Electrical Engineer
DCC Website & NMRA DCC Clinics: www.markgurries.com




Re: RC Snubber question

Mark Gurries
 

On Aug 8, 2014, at 3:52 PM, esimard@yahoo.com [WiringForDCC] <WiringForDCC@yahoogroups.com> wrote:

Hi, all

I have a main buss, unbreakered, in the shape of a Tee. The command Station is in the middle with a three foot run to the middle of the Tee.
Good, this divides the main bus up into two smaller busses.

Each ide leg of the Tee is 25 feet long. At the end of these two legs are two PSX breakers with their output going to about 10 feet of breakered sub mains.
So we are talking a NET wire length of 35 feet which puts it past the 30Ft point.


If I place an RC Snubber at the cmd station
No need to place one at the command station (Booster) location (Most but not all command stations have a built in booster.) See comments at the bottom.

should I place others at the end of each 25 foot main,
Yes. The booster located in the middle electrically divides the bus up into two smaller independent main busses. Stated another way, all buses start at the booster location no matter how many their are.

before each PSX breaker
This is not the best location to place your first RC filter. The PSX breaker does not care about nor affected by the RC filter. They are not part of the picture of RC filter placement.

The only time RC filter placement can cause problem is if you have track "occupancy detectors" the monitor track current. If you do not know what a occupancy detector is, then you have nothing to worry about.

or at the end of the 10 foot breakered sub mains?
Yes. The best place to put your FIRST RC filter is always at the very end of the main bus. Placing it at the end of the 10Foot extension actually places it at the end of the 35 Foot bus run.

What is the recommended practice?
Always put your FIRST RC filter at the end of the bus. You can add more if needed anywhere along the line if problems are found.

NCE Cmd Station
Command Stations drive boosters and booster drive the track.

NCE "starter systems" always consist of a "command station" and a “booster" sold together in some form of packaging.

Examples of two forms of NCE DCC system packaging for starter systems:

1) The 5A PowerPro system consist of a command station called the CS02 and a 5A booster called the PB105A in a single box.

2) The 10Amp PowerPro system consist of a command station called the CS02 in it's own box and a 10A booster in its own box for a total of two boxes.

You can buy just a command station all buy itself and you can buy just boosters all by themselves too. But you must have one command station to make a DCC system work. You can have lots of boosters.

This is why I say the main buss AKA track bus always starts at the booster since the is the most accurate statement that works with ANY DCC system regardless of brand of packaging.

Best Regards,

Mark Gurries
Electrical Engineer
DCC Website & NMRA DCC Clinics: www.markgurries.com


Re: RC Snubber question

jazzmanlj
 

No need for a snubber near the command station as it's built in. Putting  in more is a an open discussion. In some instances it causes problems instead of fixing them.


RC Snubber question

esimard
 

Hi, all

I have a main buss, unbreakered, in the shape of a Tee.  The command Station is in the middle with a three foot run to the middle of the Tee.  Each ide leg of the Tee is 25 feet long.  At the end of these two legs are two PSX breakers with their output going to about 10 feet of breakered submains.


If I place an RC Snubber at the cmd station should I place others at the end of each 25 foot main, before each PSX breaker or at the end of the 10 foot breakered submains?


What is the recommended practice?


NCE Cmd Station


Thanks in advance

_Ernie


French translation, was Using a Bi-Polar LED Polarity To Test

CS_listes
 

For Allan Gartner

Hello Allan,
I am the creator and moderator of the forum "ZIMO in French."
I want to translate the next chapter of your site, to publish it on our forum:
"Signaling Circuits contributed by Don Vollrath."
http://www.wiringfordcc.com/signaling.htm

Can I have your permission to do it?

With thanks.
Good day digital.
Charles_Soubiran_Bordeaux_France.


Traduction en français, était Using a Bi-Polar LED To Test Polarity

A l'attention d'Allan Gartner

Bonjour Allan,
Je suis le créateur et le modérateur du forum "ZIMO en français"
Je souhaite traduire le chapitre suivant de votre site, pour le publier sur notre forum :
"Signaling Circuits contributed by Don Vollrath."
http://www.wiringfordcc.com/signaling.htm

Puis-je avoir votre permission de la faire ?

Avec mes remerciements
Bonne journée en numérique.
Charles_Soubiran_Bordeaux _France.


Re: Using a Bi-Polar LED To Test Polarity

redking56@...
 

Thanks, Don, I used the 3 leg bi-polar LED.   Very cool.

Rich


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

Yes, but it takes the 3-wire type to do it. See http://www.wiringfordcc.com/signaling.htm

DonV

 

From: WiringForDCC@... [mailto:WiringForDCC@...]
Sent: Wednesday, July 30, 2014 7:20 AM
To: WiringForDCC@...
Subject: [WiringForDCC] Using a Bi-Polar LED To Test Polarity

 




Is it possible to use a bi-polar LED to test the polarity of the two rails (e.g., the LED lights green one way and red if the two legs are flipped the other way)?

 

Thanks.

 

Rich





Re: Using a Bi-Polar LED To Test Polarity II

Glenn
 

Trying again J

 

All Electronics list several two lead bi-polar LED’s.

http://www.allelectronics.com/make-a-store/category/340080/leds/bi-color/rgb/1.html

 

Be sure to include the resistor.

 

Glenn

 


From: WiringForDCC@... [mailto:WiringForDCC@...]
Sent: Wednesday, July 30, 2014 08:20
To: WiringForDCC@...
Subject: [WiringForDCC] Using a Bi-Polar LED To Test Polarity

Is it possible to use a bi-polar LED to test the polarity of the two rails (e.g., the LED lights green one way and red if the two legs are flipped the other way)?

Thanks.

Rich


Re: Using a Bi-Polar LED To Test Polarity

Glenn
 

All Electronics list several two lead bi-polar LED’s.

 

Be sure to include the resistor.

 

Glenn

 


From: WiringForDCC@... [mailto:WiringForDCC@...]
Sent: Wednesday, July 30, 2014 08:20
To: WiringForDCC@...
Subject: [WiringForDCC] Using a Bi-Polar LED To Test Polarity

 




Is it possible to use a bi-polar LED to test the polarity of the two rails (e.g., the LED lights green one way and red if the two legs are flipped the other way)?

 

Thanks.

 

Rich


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