Re: Hot Snubber

Vollrath, Don <dvollrath@...>
 

The dissipation heat in the resistor for a DCC bus snubber will be in direct proportion to the value of the capacitor. The 100-220 ohms value of the resistor makes little difference.

0.1   microfarad is the ideal value. 0.47 uF is too big and will cause the resistor to run very hot. 0.01 uF is too small and not add enough ‘noise’ suppression to help the situation. Any type of non-polarized capacitor, except for tantalum, will be sufficient. 0.1 uF, 50V ceramic caps are adequate, small and inexpensive.

 

Yeah… RShack first substituted R/C toys then cell phones do-dads for audio amps, speakers and other useful electronic parts in many stores. That has shown up on the yearly spreadsheets as a poor business decision.

DonV   

 

From: WiringForDCC@... [mailto:WiringForDCC@...] On Behalf Of asychis@...
Sent: Friday, March 07, 2014 8:49 AM
To: WiringForDCC@...
Subject: [WiringForDCC] Re: Hot Snubber

 




A couple of questions:

 

I take it that a "snubber" is the same as a buss terminator?

 

If you are using snubbers to terminate all your busses, do they all need to use the same value for the resistor and capacitor?  It looks like the recommended values are 100 ohms and .1 mfd for the resistor and capacitor, respectively.

 

What are the consequences of changing these values?  If I had one snubber with a 100 ohm resistor and .1 mfd cap and another with a 100 ohm resistor and a .47 mfd cap, would there be problems?

 

I am starting to terminate all our busses on the club layout and want to make sure I get it right.  I thought I could easily pick up the components at Radio Shack, but at least in Amarillo they carry few components these days.  Mainly bits and pieces.  In all the Radio Shack stores in Amarillo I found six ceramic and four mylar .1 mfd capacitors.

 

That leads to a final question, is there any problem mixing ceramic, mylar and other types of non-electrolytic caps?

 

Thanks!

 

Jerry Michels

Amarillo Railroad Museum




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