Author Topic: snubbers  (Read 519 times)

Ken Z

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snubbers
« on: July 02, 2019, 10:31:04 PM »
I have seen people talk of adding snubbers to their NCE layouts.  I have a friend who added "capacitors" to his Digitrax layout and then removed them because they didn't work.  (whatever that meant) I have a large layout with Digitrax and my power is split into 4 districts with 70 foot runs.  I have had no issues however I would always want to error on the side of making things as bullet proof as possible.  I don't want to add something not necessary, that seems snobish but if it is prudent to snub, I am glad to do that.   

Ken Zieska
Ken Zieska

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Re: snubbers
« Reply #1 on: July 02, 2019, 10:55:35 PM »
Snubbers help suppress high voltage spikes which can do serious damage to DCC decoders. The longer the bus wire run the more the issue becomes something to become concerned about. If your runs are 70ft long I'd certainly suggest adding them. For their cost compared to a blown decoder (like a LokSound or SoundTraxx) it can only be worth it.

A snubber is actually just a single capacitor and resistor connected across the bus at the end, forming a terminator. You could by the components for less than a dollar per snubber or even buy them ready made.

Alan Gartner's site goes into it a bit at http://www.wiringfordcc.com/track_2.htm in the section "Considerations for Layouts with Long Bus Wires". It's worth the read.

- Tim

TwinStar

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Re: snubbers
« Reply #2 on: July 04, 2019, 06:33:13 PM »
Does the same concept apply to a fixed DC layout?
Jacob Damron
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Alan

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Re: snubbers
« Reply #3 on: July 04, 2019, 06:58:48 PM »
Yes, although a DCC buss is somewhat more sensitive for one additional reason. In addition to the electrical noise on the buss caused by running electric locos, both DC and DCC can suffer from power-on and short circuit spikes that cause voltage 'ringing' on the bus - voltage overshoot and undershoot as the system stabilizes after a transient event. DCC, unlike DC, suffers control signal integrity from ringing on the buss. Too much ringing equals signal loss. Snubbers can help dampen spikes and suppress ringing in both cases however, are not generally needed on a DC layout unless the bus is especially heavy and long. If power supply capacity is of no concern you can also dampen a DC bus (RailPro DC bus) with a simple resistive load.

http://www.lkorailroad.com/powering-the-lko-part-iii/
and
http://www.lkorailroad.com/big-honkin-resistors/
Alan

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When I was a kid... no wait, I still do that. HO, 28x32, double deck, 1969, RailPro