Date   
Re: Hot Snubber

redking56@...
 

Hi Len,

To answer your questions, 

No, the bus wires are not twisted, and the two bus wires are pretty much right next to each other.

Regarding the hot snubber, I would have never noticed it except for the fact that I was working on some wiring under the layout and happened to notice it.  I wonder how many modelers ever check the snubbers since they are under the layout, out of sight and out of mind.

I cannot help but wonder, why this particular snubber?  If "the snubber is doing its job as intended", what is it doing, and how would it be noticed except by chance.

I go back to my original question.  Why is this particular snubber hot, and is it anything to be concerned about?

I really appreciate all of the help and attention that this thread has brought on, but I remain mystified as to whether I have a problem and, if I do, how to fix it.

Rich

Re: Hot Snubber

Skip Barber
 

Rich,
I would open the loop, at the end between the red and blue dot and see if the snubber cools. Everything should still run fine. If you just cut it, it could be reconnected with butt splices if you indeed want to. I would leave it open, myself. 

Skip Barber


On Mar 15, 2014, at 8:25, <redking56@...> wrote:

Hi Len,

To answer your questions, 

No, the bus wires are not twisted, and the two bus wires are pretty much right next to each other.

Regarding the hot snubber, I would have never noticed it except for the fact that I was working on some wiring under the layout and happened to notice it.  I wonder how many modelers ever check the snubbers since they are under the layout, out of sight and out of mind.

I cannot help but wonder, why this particular snubber?  If "the snubber is doing its job as intended", what is it doing, and how would it be noticed except by chance.

I go back to my original question.  Why is this particular snubber hot, and is it anything to be concerned about?

I really appreciate all of the help and attention that this thread has brought on, but I remain mystified as to whether I have a problem and, if I do, how to fix it.

Rich

Re: Hot Snubber

redking56@...
 

Skip, between the red and which blue dot?
I went back and numbered the snubbers in the Photo file to make it easier to reference.
Rich


---In WiringForDCC@..., <skip_8933@...> wrote :

Rich,
I would open the loop, at the end between the red and blue dot and see if the snubber cools. Everything should still run fine. If you just cut it, it could be reconnected with butt splices if you indeed want to. I would leave it open, myself. 

Skip Barber



Re: Hot Snubber

colinseggie@...
 

Hi Rich,
Before you cut the Bus as Skip suggests. Cut one lead of the RC Filter (snubber ) run your trains and check if any of the other snubbers get hot. And which one?
Doc Colin

Re: Hot Snubber

Skip Barber
 

Rich,
Between 3 and 4 would be best. Would that make approximately equal length runs?


Skip Barber


On Mar 15, 2014, at 8:56, <redking56@...> wrote:

Skip, between the red and which blue dot?
I went back and numbered the snubbers in the Photo file to make it easier to reference.
Rich


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

Rich,
I would open the loop, at the end between the red and blue dot and see if the snubber cools. Everything should still run fine. If you just cut it, it could be reconnected with butt splices if you indeed want to. I would leave it open, myself. 

Skip Barber



Re: Hot Snubber

jazzmanlj
 

Rich,

>No, the bus wires are not twisted, and the two bus wires are pretty much right next to each other.
As I suspected! Having the wires as you describe increases the parasitic inductance and capacitance! These cause problems
>Regarding the hot snubber, I would have never noticed it except for the fact that I was working on some >wiring under the layout and happened to notice it. I wonder how many modelers ever check the snubbers >since they are under the layout, out of sight and out of mind.
Probably true for the majority of modelers. The anamolies are hard to see without instruments like an Oscope.
>I cannot help but wonder, why this particular snubber? If "the snubber is doing its job as intended", what is it >doing, and how would it be noticed except by chance.
It is supressing voltage spikes that seem higher than usual. That is it's main job!  As to why, every layout is unique to itself. No different than any piece of switching electronics. This is what engineers deal with all the time.
Do a Google search on 'snubber waveforms'. Lots of pictures so all can get a better understanding of what a snubber does and why it is needed in certain circumstances.
>I go back to my original question. Why is this particular snubber hot, and is it anything to be concerned about?
Yes you should be concerned. Voltage spikes are undesired and can cause problems and even destroy decoders that are not protected(poorly designed)!
>I really appreciate all of the help and attention that this thread has brought on, but I remain mystified as to >whether I have a problem and, if I do, how to fix it.
Twist all your main buss wires. You can do a section at a time and at least feel if a snubber gets a bit cooler.
Keep any sensitive wires such as control away from the power wires, and if you have control/signal wires of any length then twisting is a must. Shall be twisted.
 
Hope this helps,
Len Jaskiewicz


 

Re: Hot Snubber

redking56@...
 

If the solution is to twist the bus wires, then I am going to have to live with the problem.

At this stage of my layout development, twisting the bus wires would be an enormous undertaking, what with feeders connected and bus wires anchored, etc, etc.  Ain't gonna happen.

Now, I will remind everyone who is following this thread that when I replaced the hot snubber yesterday, the new snubber is a lot less hot.  The resistor is a bit warm, but I can grasp it in my fingers.  At this time, it is no warmer than most of the other snubbers on my bus wires.

What if I took that hot snubber and inserted it somewhere on the bus wires, perhaps near one that is cooler?

Rich

Re: Hot Snubber

Charlie Sleep <csleep@...>
 


So effectively, that resistor is dissipating 0.31 watts normally and so you need at least a 1/2 watt resistor?
Thanks.
 
Charlie

-----Original Message-----
From: WiringForDCC@... [mailto:WiringForDCC@...]On Behalf Of Vollrath, Don

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. ( r egardless of the value of the resistor if it is about 100 ohms).

 DonV

 

Re: Hot Snubber

Skip Barber
 

Rich,
Open the loop, I'll bet you see a difference. And it costs you nothing in time or money. 

Skip Barber


On Mar 15, 2014, at 9:16, <redking56@...> wrote:

If the solution is to twist the bus wires, then I am going to have to live with the problem.

At this stage of my layout development, twisting the bus wires would be an enormous undertaking, what with feeders connected and bus wires anchored, etc, etc.  Ain't gonna happen.

Now, I will remind everyone who is following this thread that when I replaced the hot snubber yesterday, the new snubber is a lot less hot.  The resistor is a bit warm, but I can grasp it in my fingers.  At this time, it is no warmer than most of the other snubbers on my bus wires.

What if I took that hot snubber and inserted it somewhere on the bus wires, perhaps near one that is cooler?

Rich

Re: Hot Snubber

jazzmanlj
 

Rich,

 

>What if I took that hot snubber and inserted it somewhere on the bus wires, perhaps near one that is cooler?
 
You replaced the resistor with a higher power than the others, correct? Naturally it will run cooler! A resistor is meant to dissipate energy based on Ohm's law.
Do not move the snubber! Go to a higher power resistor if need be so it runs cooler. You have a trouble spot and the snubber is doing it's intended job!
Len Jaskiewicz


Re: Hot Snubber

redking56@...
 

OK, I posted a new diagram in the Photos section to illustrate the setup of #3 and #4 snubbers.  If I disconnect #4, then should I add a snubber to the right of the disconnected bus wires?

Here is another question.  Does it matter how many feeders are between two snubbers?

Does it matter what type of device is connected to a feeder besides rail, such as an NCE Switch-It or Mini-Panel or Circuitron Flasher, or Digitrax AR-1?

Rich



Re: Hot Snubber

Flash Gordon
 

Rich,

I posted a solution in your photo folder. You can remove it if you do not agree.

As others have said, it shows the loop as open. I can see no advantage in having a closed loop so this solution will not change how the layout operates. The track at that point also has to be gapped, both rails. Just cut with Dremel cut off wheel. Later fill the gap with plastic so they do not creep together.

Some more back ground.

If you read any of the instruction for DCC you will see that bus longer than 30 feet can cause problems. The problem would be spikes in the signal along the bus. These spikes can harm decoders.

If the wires are twisted, the problem will be reduced, since yours are not I am thinking that is the problem.

In layman's terms, the snubbers (R/C Filters) act as sponges and soak up the spikes.

Also if possible, tie each of the two wires in a bus together with wire ties or tape. The closer the pairs are the less likely to cause the spike problem.

As to the hot R/C filter, it may be damaged and I would replace it to eliminate that variable.

Ed S

Re: Hot Snubber

redking56@...
 

Len, if I have a "trouble spot", can you speculate for me on what might produce a trouble spot?

Rich

Re: Hot Snubber

jazzmanlj
 

>So effectively, that resistor is dissipating 0.31 watts normally and so you need at least a 1/2 watt resistor?
That is correct and thanks to Don for such a good explanation.
Might I add that it is common practice that components are generally de-rated in use so as not to run them at or near the max. If a 50% de-rating is used then a 1W resistor would be desired.

 

Len Jaskiewicz


Re: Hot Snubber

redking56@...
 

Ed, if I open the loop at that point, you say to gap both rails at that point.

Help me out with that a little.  Where exactly would I gap the rails?

I very well understand the concept of gapping rails, several reversing sections on my layout and some sections gapped for occupancy detection.  But why and where would I gap the rails when I open the bus wires?

Rich


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

Rich,

I posted a solution in your photo folder. You can remove it if you do
not agree.

As others have said, it shows the loop as open. I can see no
advantage in having a closed loop so this solution will not change
how the layout operates. The track at that point also has to be
gapped, both rails. Just cut with Dremel cut off wheel. Later fill
the gap with plastic so they do not creep together.


Re: Hot Snubber

Flash Gordon
 

Wait I will change the drawing.

Ed S


At 10:07 AM 3/15/2014, you wrote:
 

Ed, if I open the loop at that point, you say to gap both rails at that point.

Help me out with that a little.  Where exactly would I gap the rails?

I very well understand the concept of gapping rails, several reversing sections on my layout and some sections gapped for occupancy detection.  But why and where would I gap the rails when I open the bus wires?

Rich


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

Rich,

I posted a solution in your photo folder. You can remove it if you do
not agree.

As others have said, it shows the loop as open. I can see no
advantage in having a closed loop so this solution will not change
how the layout operates. The track at that point also has to be
gapped, both rails. Just cut with Dremel cut off wheel. Later fill
the gap with plastic so they do not creep together.


Re: Hot Snubber

Flash Gordon
 

Rich,

New drawing posted.

Feeders....  rule of thumb.  Every 6 to 10 feet.

Ed S


At 10:07 AM 3/15/2014, you wrote:
 

Ed, if I open the loop at that point, you say to gap both rails at that point.

Help me out with that a little.  Where exactly would I gap the rails?

I very well understand the concept of gapping rails, several reversing sections on my layout and some sections gapped for occupancy detection.  But why and where would I gap the rails when I open the bus wires?

Rich


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

Rich,

I posted a solution in your photo folder. You can remove it if you do
not agree.

As others have said, it shows the loop as open. I can see no
advantage in having a closed loop so this solution will not change
how the layout operates. The track at that point also has to be
gapped, both rails. Just cut with Dremel cut off wheel. Later fill
the gap with plastic so they do not creep together.


Re: Hot Snubber

Flash Gordon
 

Rich,

You really should read these two pages.... Part 1 and part 2

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

Skip the sections about tail light bulbs.... your circuit breakers will replace them.

Ed

Re: Hot Snubber

jazzmanlj
 

Len, if I have a "trouble spot", can you speculate for me on what might produce a trouble spot?

Rich,
I'm trying my best to explain this to you and everyone else here! The DCC track power is a switching square wave with sharp rising and and falling edges. Parasite components such as inductance and capacitance due to wiring is inevitable! These cause excessive spiking of voltage at the rising and falling edges!
Twisting of wires or much wider separation, etc. is common practice to reduce the parasite components. It is very common practice to place snubbers(transient supressors) at a trouble spot to reduce the spiking.
I'd like all to at least do the Google search on 'snubber waveforms' as well as a Wiki search on 'snubber' versus 'R/C filter' so we all get a better understanding!
Learning and problem solving go hand in hand! Mere speculation leads to misconceptions.
Regards to all,
Len Jaskiewicz

Re: Hot Snubber

redking56@...
 

To my non-electrical engineer's mind, these comments are way over my head.

Are you saying that my failure to twist my bus wires are the cause of a hot snubber and, if so, why only one and why this one?

What on the layout, or what it is about my layout, other than non-twisted bus wires, could cause this to happen?

Rich


---In WiringForDCC@..., <len.jask@...> wrote :

Len, if I have a "trouble spot", can you speculate for me on what might produce a trouble spot?

Rich,
I'm trying my best to explain this to you and everyone else here! The DCC track power is a switching square wave with sharp rising and and falling edges. Parasite components such as inductance and capacitance due to wiring is inevitable! These cause excessive spiking of voltage at the rising and falling edges!
Twisting of wires or much wider separation, etc. is common practice to reduce the parasite components. It is very common practice to place snubbers(transient supressors) at a trouble spot to reduce the spiking.
I'd like all to at least do the Google search on 'snubber waveforms' as well as a Wiki search on 'snubber' versus 'R/C filter' so we all get a better understanding!
Learning and problem solving go hand in hand! Mere speculation leads to misconceptions.
Regards to all,
Len Jaskiewicz