Brent
"All of the world's problems are the result of the difference between how we think and how the world works."
The Snubber acts as a RC (resistor/capacitor) filter.
All of the power buss lines have noise on them and as the length of the power buss gets longer the noise gets greater.
When the noise gets too much the DCC signal gets lost in the noise and the decoder misses commands and you then think that there is a problem when in fact the decoder just missed the command due to the noise.
The Snubber bypasses the noise to ground (for lack of a simple explanation).
I had this problem on a 60 ft run and the engines would just runaway even with the keypad plugged in. The engine once started would not respond to any command. And it was only with certain engines. Others would work fine.
I also had problems with runaways on the other end of the layout but only after operating for more than 3 hours and then this would not always happen (so it was really hard to trouble shoot) change engines and it went away (which lead me to believe it was the engine decoders – but operated fine closer to the center of the layout – where the command station was).
Once I put the Snubber on the ends of the long Power Buss lines the problems went away and have never came back!
And this was on a Digitrax system not a NCE one! So this is not limited to just NCE.
BOB H – Clarion, PA
It takes an iron man to play with a toy iron horse.
cacole wrote:We've been running DCC for almost 10 years on a 20x40 foot HO scale club layout and have never had any problems with spurious noise in the buss lines, and this is the first time I have ever heard of needing a noise filter on one.
Me thinks , local enviroment can be the cause or lack of spurious noise. Close transmitters, hi tension line over the house. Things like that. Even some house hold appliances, those cheaply built without r/c networks in them to prevent line back feed.
Jerry SP FOREVER http://photobucket.com/albums/f317/GAPPLEG/
I did not need the Snubber at first (the first 3 years) but as I kept adding track and more equipment (2900 feet of track) the problem would only happen randomly after 4 or 5 hours or so (I hold 12 hours OP Till U Drop sessions) and this is with 20 to 30 operators.
I kept thinking that this was a bad decoder or something as it was initially only affecting certain engines in the one area of the layout.
Then during my last building spree I added a 4 track staging yard and the resulting Buss line (which was on its own circuit breaker!) the END of the buss ended up being 60 feet from the command station (that is 120 ft of #12 wire – up and back).
The runaway problem just started showing up after a 3 hour session one Thursday night OPs. You could not control any engines in the new staging area, once started they just refused to respond to any commands from the Keypad. If I tilted the engine to break contact then it would stop. But once I would give it the command again to move again it would begin moving but and subsequent commands were ignored.
Now to add the Snubber I just made a resistor and cap in series and mounted it on a circuit board with two wire ends. I soldered a two position terminal strip to the end of the Power Buss and then added the Snubber to the terminal strip (effectively across the white and Black wires) The younger members of my OPs group state that they can hear the Snubber singing but us older folks can’t hear this hi-pitched squeal.
I have to get around to moving it to the back side of the benchwork so it will hopefully be less noticeable (sound wise).
The reason for the terminal strip was to make a neat install and if I had to make a revision to the Snubber (make it a little more aggressive) I could do so quickly.
I then went to the other end of the basement and added another Snubber to the one run there that had occasional runaways and it too has stopped having any problems.
I added other terminal strips to the ends of some of the longer buss runs just in case I might run into the problem with other sections of the layout but so far I had no more problems.
But it still may show up as I am planning on adding additional trackage with a proposed Sun room up stairs and the additional basement room down stairs.
Now will you need a Snubber on your layout? Doubtful! But if you end up having real long buss runs and your wiring is marginal (less than #12 and drop wires soldered every 3 feet) then you could run into this problem.
I thought that I would not have the problems as I was using #12 wire and in some places I was using #8 wire and had track drop wires every 3 feet and on all three ends of every turnout to eliminate any resistance in the wiring. AND it worked perfect for over 3 years but I kept adding track and I guess that it finally got to the point that it could no longer keep the noise to a level that the decoders could plow through the noise level without the Snubber.
I was skeptical that it would even work but when I added the Snubber to the staging area and the problem engines immediately came back into complete control. Pretty much answered that question. I even tried removing the Snubber and it went back to the problem immediately.
cmrproducts wrote: ...to eliminate any resistance in the wiring.
Mark P.
Website: http://www.thecbandqinwyoming.comVideos: https://www.youtube.com/user/mabrunton
Brunton
Yep I finally did it!
BOB H - Clarion, PA