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CV's for working LED ditch lights with a Digitrax decoder?

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  • Member since
    February 2002
  • From: Reading, PA
  • 30,002 posts
Posted by rrinker on Tuesday, April 17, 2012 4:35 PM

 Bummer. It's all in the way the PWM outputs for the functions are configured. Surprised they've never made an update for LEDs, since LEDs are more and more common these days.

              --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    July 2003
  • From: Metro East St. Louis
  • 5,743 posts
Posted by simon1966 on Tuesday, April 17, 2012 7:22 AM

All test so far have been with 1K in parallel per the Yahoo group.  So at the last count 1K parrallel 47K in series.  I'll double up the parallel to see what happens. 

Simon Modelling CB&Q and Wabash See my slowly evolving layout on my picturetrail site http://www.picturetrail.com/simontrains and our videos at http://www.youtube.com/user/MrCrispybake?feature=mhum

  • Member since
    February 2002
  • From: Reading, PA
  • 30,002 posts
Posted by rrinker on Tuesday, April 17, 2012 6:22 AM

 The idea posted on the Digitrax list to put another resistor in parallel with the LED may help. Try back with 1K again, so that ther are 2 1K resistors between the function and blue, and then the LED connects between the junction fo the resistors and blue. It sounds liek a dead short through the resistors but Ohm's Law says even without the LED that puts only a 6ma load on the function output at 12V, because of the 2K total resistence.

              --Randy


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    July 2003
  • From: Metro East St. Louis
  • 5,743 posts
Posted by simon1966 on Monday, April 16, 2012 9:57 PM

Well Randy I am up to 47K and still can't get the darned thing to turn off!  Time to go to Radio Shack to get some larger resistors or give up and go the TCS route.

Simon Modelling CB&Q and Wabash See my slowly evolving layout on my picturetrail site http://www.picturetrail.com/simontrains and our videos at http://www.youtube.com/user/MrCrispybake?feature=mhum

  • Member since
    February 2002
  • From: Reading, PA
  • 30,002 posts
Posted by rrinker on Saturday, April 14, 2012 8:02 PM

 You probably won't, unfortunately. Digitrax decoders just don't shut the power off enough for LEDs to use the special effects.

 You might try using larger than normal resistors, such that the 'off' part of the flashign cycle ends up being below the LED's minimum current, the 'on' should still be enough. It's a tricky thing, probably trial and error - might be best to play around with this at the workbench, with clip leads or even a solderless breadboard if you have such a thing. Case in point, my Stewart Baldwin switchers, I replaced the orange LED they supplied with my usual golden-white ones. There is already a resistor in place but it is smaller than 1K (still within limits for the LED, so it didn;t pop), so I unsoldered one end and added a 1K in series, so the total resistence is now more than 1K, which is what I usually use. The 'lenses' on these locos must be extra good optically, because it's really still TOO bright and I need to go back and put something bigger in place, like a 2,2K, 2.7K, or 3.3K. If one is still too bright and the next step is too dim, you'll have to get somehting more precise - the values I gave are for the typical 10% tolerance resistors, so if 2.7K is still too bright and 3.3K makes the LED not even come on, you have to go to 5% or 1% to get any values in between.

 Or, much of a pain as it is, install a TCS FL2 to run the ditch lighs, TCS decoders work quite well with LEDs, and even have a CV to fine tune it. Out of the box they are usually set for incandescent bulbs, so when I do somehting liek RUle 17 dimming, the 'dim' is barely different from the 'bright'. Adjusting CV64 to a lower value like 2-4 (the default is 16) dims the LEDs nicely.

 

                           --Randy


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    July 2003
  • From: Metro East St. Louis
  • 5,743 posts
CV's for working LED ditch lights with a Digitrax decoder?
Posted by simon1966 on Saturday, April 14, 2012 7:33 PM

Installing an SDH164D installed in an Athearn Genesis SD70ace.   At the same time took the opportunity to replace the burned out bulbs in the ditch lights with LED's.  BTW, it sounds great, have done the fixes to seal the speaker box, have downloaded and installed the sound file for UP 1983 from the Digitrax Sound Depot (Our loco is 1982) so I am fine with the sound.

BUT, I can't get the ditch lights to work to my satisfaction.   I use Decoder Pro and have been tweaking CVs, but the best I can get is ditch light rhythmic dimming associated with and F2 press.   The LED's noticeably dim in a ditch light alternating flashing, but they far from go out.  I have a horrible feeling this is simply the way that the decoder works and that it can't handle LED's like a trusty TCS decoder.  Anyway, thought I would throw it out there to see if there are any magic CV settings that will get the LED's to actually flash, rather than just dim and brighten.

Simon Modelling CB&Q and Wabash See my slowly evolving layout on my picturetrail site http://www.picturetrail.com/simontrains and our videos at http://www.youtube.com/user/MrCrispybake?feature=mhum

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