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Loksound v4 and asymmetric brake.


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I now have two loco's with Loksound v4 decoders that are acting rather strange. They both pick and choose.when they are going to stop on abc sections. I watched one for 30 mins and it behaved. As soon as I wash looking it slipped past a section and caused chaos. Can anyone help with cv's to make them more reliable?

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I don't think CVs are able to "adjust" sensitivity to ABC braking - more an on/off situation and then adjust the braking time/distance. However, I did experience a similar thing with one of my similarly equipped locos but cured it by the tried and trusted method of cleaning the track and wheels. How this solved the problem I have no idea but can only guess that dirty track was messing with the signal. Also, maybe there is an intermittent problem with the ABC unit itself.

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12 minutes ago, JST said:

I don't think CVs are able to "adjust" sensitivity to ABC braking - more an on/off situation and then adjust the braking time/distance. ........

 

ESU Loksound V4.  Sensitivity threshold for ABC braking, CV134.    Determines how much asymmetry in the DCC signal is needed to trigger the actions.  Page 43 of ESU English language manual.    

 

The other question is the design of the braking circuits.  If commercially bought ones, I assume they're done properly.  If DIY, were they "fast recovery diodes" or just any old cheap rectifier diodes ?   If the latter, may not be reliable.  

 

 

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I use three types of diode unit. Two are commercial and then there are my home made lash ups. I watched one loco with v4 and it behaved everywhere. I got more trains running after a while and it started to misbehave. This morning it once again ran happily with the railway to itself stopping at signals keyed to danger.  I have a Bachmann 101 with sound that follows the signalling perfectly no matter how many trains are on the move. 

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Is it possible that the other trains moving are causing a slight drop in the overall track voltage just enough that the decoder can't "see" enough of a difference between the two rails to know it needs to brake?

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48 minutes ago, LNERGE said:

I use three types of diode unit. Two are commercial and then there are my home made lash ups. I watched one loco with v4 and it behaved everywhere. I got more trains running after a while and it started to misbehave. This morning it once again ran happily with the railway to itself stopping at signals keyed to danger.  I have a Bachmann 101 with sound that follows the signalling perfectly no matter how many trains are on the move. 

 

So, it sounds like the threshold in the problematic loco is "near the limit" for that particular decoder and loco combination.   (It will be decoder plus loco plus layout - all can influence what goes on.   ).    So, if it remains a problem, you'll have to try adjusting the threshold CV to see if it improves, or gets worse: adjusting the value in a direction to make it worse will tell you to "adjust in other direction".  

Should be possible to adjust with ops-mode change whilst running loco on mainline to see how things behave.  

 

I've no idea what diodes were used in your home-brew units.    

 

- Nigel

 

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Dear RMWebbers,

 

I'm in the process of building my next exhibition layout, which is fundamentally reliant on Asym Braking with Lok Select (US outline) and an occasional V4 decoder. ( I standardised on Selects, but found myself a couple-short, and the V4s were going-cheap right when I needed them...)

 

Literally using "common as mud" 1N4001 sillicon diodes,

(No zeners, "High Spec", "Fast recover", or other excess $$$ options diodes here...)


in 5-diode packs (4-in-series + 1-bypass config),
with a bog-stock NCE Powercab FW1.65b + MiniPanel acting as a pseudo-"dumb timer/reverser",

 

and "stop within 5mm of last-powered-axle crossing the gap"
(using the "constant braking distance" CV set at absolute minimum, 
independent of the CV3/CV4 "Momentum"/Decel rates).

 

is both reproducible, reliable, and confidence-inspiring...
(exactly what an Exhibition layout demands...)

 

Just a pity SoundTraxx don't support the NMRA-spec CV27 Asym Braking modes...

 

Happy Modelling,
Aim to Improve,
Prof Klyzlr

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