Decoders with keep-alive caps: Reading with JMRI

[tstage]

Greetings -

I have a few decoders with keep-alive caps connected to them and two in particularly - one TCS Wow! and one Loksound Select - JMRI has difficulty reading the CVs accurately - i.e. inconsistent values, doesn't recognize manufacturer or decoder, etc.  (Interestingly enough, the Loksound Select in my Stewart VO-660 switcher with the "home-made" keep-alive circuit it can read...sometimes.)  All other decoders JMRI has no issues with in that regard.

I am interesting in understanding what does the introducation of the keep-alive do to JMRI that makes it difficult for it to read the CVs properly?  FWIW, I'm using JMRI connected to a 8" Windows 10 tablet.

[Edit: I should add that my Power Cab also has issues reading CVs consistently with KA-equipped decoders in programming track mode.  While I can successfully program an address, reading it back gives me different values every time.  Same with CV29.]

Thanks,

Tom

[crusader27529]

The issues are most likely related to the fact that most DCC systems do NOT keep power when using the programming track, and the KA caps must charge. That causes a delay that blocks the detection of the current pulses that DCC uses when reading the CV values.

 

It's not releated to JMRI, but the DCC system that it's connected to.

 

[Stevert]

crusader27529

The issues are most likely related to the fact that most DCC systems do NOT keep power when using the programming track, and the KA caps must charge. That causes a delay that blocks the detection of the current pulses that DCC uses when reading the CV values.

 

It's not releated to JMRI, but the DCC system that it's connected to.

 

This ^^^^

I only have one loco with a keep-alive (a WOW121), and JMRI reads it with no problem.  FWIW, I use a PR3 in stand-alone programming mode with an 18VDC power supply.

[tstage]

Thanks, crusader and Steve.  So, once a KA cap is fully-charged, would the issue go away?  If so then I would guess that the length of time needed for that would vary according to the size of the KA cap.

As mentioned in my edited post above, with my Power Cab I have no problem reading individual CV values in programming track mode with decoders that have KAs attached to them.  The issue is that the values for some CVs are different each time they are read.

Tom

[7j43k]

I've installed KA in two "locomotives":

a brass gas-electric got a full Sountraxx system.  I cannot read the CV's.  So I program on the main and write the changed values down.  I have changed the speed curve, the engine sound, the horn for example.  All written down.  On real paper.  In a folder.  With the road and road number on the tab.

a Proto GP9 got a full Loksound system.  This one is specifically designed to work on the program track.  I can read CV's.

 

I believe I will use the Loksound from now on.

 

 

Ed 

[tstage]

The aforementioned decoders with the KA cap are a TCS Wow! 121 and a Loksound micro Select.

Tom

[rrinker]

 It's the capacitor inrush - again. That Baldwin you did yourself has smaller capacitance values than typical keep alives so it works ok.

 This is going to be the case with ANY two-wire keep alive. A two wire keep alive boils down to a large capacitor across the DC side of the bridge rectifier in the decoder. The three wire type used by Loksound (and I suspect the Lenz ones will also be the same) use that third wire to control the keep alive, and keep it off when on the program track, thus a Loksound decoder with the ESU PowerPack plugged in should not have issues on the program track.

 Even though they are more expensive - I don't think I will be rollign my own keep alives, except for maybe special cases where the commercial ones don't fit. Anything I outfit with sound is Loksound, so any I also add a keep alive to will use the ESU PowerPack if at all possible, despite the higher cost. The only other option is to use a plug and socket and have to open the loco every time I want to read it on the program track, or install a small switch somewhere to disconnect the keep alive circuit.

                                             --Randy

 

[Geared Steam]

I use JMRI through a Sprog interface, no issues programming with keep alives on any Soundtrax or  TCS decoders. Loksound gave me an issue, I fixed the problem by selling them. I don't believe its JMRI.