CS3 Trials and Tribulations

Greg Elmassian

Greg Elmassian

Registered
8 Mar 2014
4,053
San Diego
www.elmassian.com
I read the whole 4 pages of this thread... one thing I would say, is never put incandescent bulbs across the track, they have been shown to cause issues, since not only do they have resistive value, but inductance. I would recommend at least using a full wave bridge to feed a small constant voltage circuit, with a small noise cap on the DC side...

Greg
 
lynxface

lynxface

Registered
14 Mar 2016
40
Scotland
I read the whole 4 pages of this thread... one thing I would say, is never put incandescent bulbs across the track, they have been shown to cause issues, since not only do they have resistive value, but inductance. I would recommend at least using a full wave bridge to feed a small constant voltage circuit, with a small noise cap on the DC side...

Greg
Very interesting thanks very much Greg
 
Greg Elmassian

Greg Elmassian

Registered
8 Mar 2014
4,053
San Diego
www.elmassian.com
In large HO layouts, "snubbers" are used to "clean up" signal in places where reflections (signal) on the track can cause issues. They basically dampen some of the signal.

Almost any capacitance or inductance you add can cause issues, an inexpensive 100 MHz scope can be made from a kit (LCD screen) for about 40 dollars and you can look at the DCC signal for excessive distortion.

The best thing is if you can locate a packet analyzer, they still make some hardware that can be hooked to JMRI, and of course there is the wonderful standalone one: (which analyze packet errors, types of packets, etc)
 
lynxface

lynxface

Registered
14 Mar 2016
40
Scotland
In large HO layouts, "snubbers" are used to "clean up" signal in places where reflections (signal) on the track can cause issues. They basically dampen some of the signal.

Almost any capacitance or inductance you add can cause issues, an inexpensive 100 MHz scope can be made from a kit (LCD screen) for about 40 dollars and you can look at the DCC signal for excessive distortion.

The best thing is if you can locate a packet analyzer, they still make some hardware that can be hooked to JMRI, and of course there is the wonderful standalone one: (which analyze packet errors, types of packets, etc)
Will try and get hold of one of these machines. I did actually put a DC snubber on the layout last week.

what size cap would you recommend ? I have some full wave bridge rectifiers, but the smallest caps I have to hand are 1000uF. Is this over kill for just one or two incandescent 18v bulbs ?
 
Greg Elmassian

Greg Elmassian

Registered
8 Mar 2014
4,053
San Diego
www.elmassian.com
Ahh, for lighting very little capacitance is needed, more to reduce noise... 1000 microfarad will be fine... by design, DCC being a square wave, gives almost perfect DC when rectified... one of the reasons for the square wave...

Greg
 
  • Like
Reactions: lynxface
LGB333

LGB333

Active Member
If it is speed steps you need to change CV29. This is a tricky CV to set as there are many settings controlled by individual bits. There is a helpful calculator here:
http://www.2mm.org.uk/articles/cv29 calculator.htm
Bit 1 ("on" for 28 steps) is the relevant bit.
Folks - No need to use a CV calculator for setting CV29. The basic settings for CV29, which includes setting 14 or 28 Speed Steps, is very easy. Most factory DCC decoders use factory-set values of 28 Speed Steps in their decoders. I'm familiar with and install into customers' LGB locomotives Massoth XLS, ESU 5 XL, Soundtraxx Tsunami2 4400 series, and Phoenix PB17 (Sound Only) DCC Sound decoders, which follow this approach. If you want to set CV29 to 28 Speed Steps, which is what most DCC hobbyist use, and also set the decoder for both digital and analog operations, then set CV29=6. If you want 14 Speed Steps, and again use both digital and analog operations, then set CV29=4. Bingo!

If you want to change the driving direction, set the internal driving curve, or change from the default short Address to Long Address format, then there are additional values you need to set.......not needed by most DCC hobbyists, but if you do, then you might want to use a CV bit calculator.
 
Greg Elmassian

Greg Elmassian

Registered
8 Mar 2014
4,053
San Diego
www.elmassian.com
Still needs binary math for people who want to understand, but as Tom points out, you may only want 2 numbers, or maybe 4

14 ss no DC
14 ss with DC
28 ss no DC
28 ss with DC

oh, wait, what about long and short addresses, ok now you need 8 numbers....

oops, the motor runs backwards, now your cheat sheet is 16 numbers...

get the drift? CV29 calculators are all over the web...


Greg