Re: DCC Bus distribution and snubbers question

mgj21932
 

Carl,
Good suggestion Re: separate power switches.  
Thanks. 
Bill Demarest


On Dec 29, 2019, at 9:12 AM, Carl <carl.blum@...> wrote:



Hi Gang:

I know 34 power districts sounds like a lot. But from a trouble shooting aspect, the more you can isolate a problem to a single small district the better. Even if the districts are served by the same booster or DCC circuit breaker. It makes it easier to divide and conquer.

On my layout I have 6 boosters and 12 power districts. Each district has one power switch ( AC / DCC ) and two breakers, which do trip sometimes. If there is a problem is it nice to reach the power switch and cut power to the district until the problem is solved.

Carl.

On 12/29/2019 1:52 AM, Mark Gurries wrote:

      
On Sep 20, 2019, at 3:37 PM, Blair & Rasa <smithbr@...> wrote:

Hi
I'm planning my DCC layout for my Algoma Central at this time.  I have located three boosters, each at the root of the three peninsulas. 
Each Booster will feed quad current limiters, either PM42s or something more recent. 
However, each limiter's output will feed multiple bus segments(e.g. one bus on the upper peninsula, one on the lower, each fed by the same limiter). 
As each of those runs will exceed 30’,

      
I am wondering if I need an RC snubber at the end of each, or should I put one at the output of the limiter, before we fan out to both runs?
End of each.  Placing them close to the booster defeats the purpose of the snubber.  The goal is to install them at the far end furthest tack bus wire wise away from the booster.

In the grand schema, we have 34 sections of bus to be fed; in some cases a limiter will feed up to four segments of track,
What is the difference between a section and segments?   

I like to use consistent terms.   This is what I THINK you saying.

1) You have 3 Booster Districts.  One Booster District per Peninsula.
2) A Peninsula has 2 levels.
3) You have 34 Power Districts
4) You are using quad output DCC circuit breakers.

I think this break up as follows.

1) Average of about 34/3 ~  11 Power Districts / Booster.   
2) 3 Quad circuit breakers / Booster.
3) Each Level on a given peninula has between 5 or 6 power Districts.

This electrical design is for this large layout creates a unusually high number of power districts per booster.  That is to not say there is anything wrong.  Sounds like a lot of main line running and you getting the most coverage out of a given booster.

so if I have to put a snubber on each long run, the current drain will become significant, I think. 
It will consume about 2 HO locomotives worth.

You need 1 Snubber per power district.

Each snubber has a 100 Ohm resistor.

11 x 100 Ohm resistor in parallel  = 9 ohms.    12V / 9 Ohms = 1.32 Amps.

What you can do is replace the 100 Ohm resistor with a 200 Ohm.  The snubber will be weaker in effectiveness but still work.
 
Is it correct that I need to snub each long run, or is it effective to put a single snubber at the base of the branches?
Yes.


Best Regards,

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






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