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Dimmed LED headlights "pulsating" when using Rule 17

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Dimmed LED headlights "pulsating" when using Rule 17
Posted by tstage on Saturday, December 14, 2013 3:46 PM

Greetings,

I recently installed a TCS M1P-1" decoder into a Stewart VO-660 switcher with the following values:

  • CV61 = 49 (BEMF+dimmed when stopped+opposite dimmed)
  • CV64 = 2 (Dimmed brightness for LED headlights)
  • CV49 = 40 (front headlight bright/rear dimmed in forward)
  • CV50 = 40 (rear headlight bright/front dimmed in reverse)

The issue I'm running into is that the leading LED headlight comes on fully whenever the locomotive is moving in either direction but the opposing LED pulsates when dimmed.  This is also the case when the locomotive comes to a complete stop and both LEDs automatically dim.

This has happened with two separte but identical decoders on the same locomotive.  Is this somehow related to the BEMF being activated on CV61?  I have not seen this phenomenon using any other TCS decoder I have.

Thanks for the help...

Tom

[Oops! Embarrassed  Meant to place this in the "Electronics and DCC" forum - Sorry.]

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Posted by rrinker on Saturday, December 14, 2013 4:34 PM

 I'd suggest trying 3 or 4 for CV64, LED's don;t really 'dim' so all it does is turn the LED on and off really fast. Nore off = dimmer, but more chane of seeing the flicker. These LEDs may have slightly different characteristics than ones you've used in the past, so they need slightly different values.

 Also, if you look at the comprehensive manual, http://www.tcsdcc.com/public_html/Customer_Content/Technical_Info/Tech_Manuals/Comprehensive%20Programming%20Guide.pdf

It appears each function can be set to its own dim value, looks like CV64 just sets them all to whatever you put there, but there's a dedicated dim level setting for each function. There are, in fact, a LOT of things TCS decoders can set that aren;t mentioned in the simple getting started instruction sheet that comes with the decoders.

               --Randy

 


Modeling the Reading Railroad in the 1950's

 

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

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Posted by tstage on Saturday, December 14, 2013 4:53 PM

Randy,

Thanks for the link to the Comprehensive Programming Guide.  I actually printed that out last week.

I'll try the higher values for CV64 but, IIRC, even a value as high as "6" still pulsated.

Tom

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Posted by rrinker on Saturday, December 14, 2013 6:04 PM

 There's some other stuff for pulse frequency listed in the comprehensive guide, although that may only be for effects like the mars and strobe lights, I forget. I thought there was a seperate document just on all the lighting stuff too. It's almost crazy how many settings there are (luckily that don't need to be touched except in special cases) - I don;t think all of it is even in the JMRI definitions for TCS decoders.

 

                 --Randy


Modeling the Reading Railroad in the 1950's

 

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Posted by CSX Robert on Wednesday, December 18, 2013 10:15 AM

Do you have a DCC system that allows you to run DC locomotives?  If so, make sure the DC locomotive is set to 0 speed and see if that makes a difference.  I have noticed that when using zero-stretching(the method used for running a DC locomotive on DCC), dimmed lights on TCS decoders will sometimes flicker noticeably.

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Posted by tstage on Wednesday, December 18, 2013 11:37 AM

Robert,

I have an NCE Power Cab so - no, it doesn't allow me to run a locomotive on DC.  I do still have an MRC power pack that I could connect to a piece of spare track.

I've installed three TCS decoders recently in three separate locomotives: An M1P-1" (Stewart VO-660), an LL8-LED (IM F3), and a A4X (Proto 2000 0-8-0).  Only the A4X has exhibited the flickering issue.  I also have the M1P-1" programmed with the same dimming CVs as the A4X and it doesn't flicker at all.

Tom

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Posted by mlehman on Wednesday, December 18, 2013 2:29 PM

Tom,

How much resistance do you have in-line with the offending LEDs? If you have a little too much, it's possible that is taking the normally unseen variation that dimmed LEDs have at lower voltages and making it visible as flicker.

Mike Lehman

Urbana, IL

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Posted by tstage on Wednesday, December 18, 2013 8:07 PM

Mike,

1K resistors for both front and rear headlights, which are on the light board that came with the locomotive.

Tom

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Posted by mlehman on Wednesday, December 18, 2013 8:56 PM

OK, well that's not it.

I'm an extremist when it comes to resisters for LEDs and sometimes end up with a few thousand ohms, so was thinking maybe someone else likes them dim like I do and over did it.

Mike Lehman

Urbana, IL

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Posted by locoi1sa on Thursday, December 19, 2013 6:55 PM

Make sure the Bowser boards do not have caps on them. You may have to bypass the plug and wire the blue, white and yellow wires directly to the LEDs through a 1K resistor.

       Pete

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Posted by rrinker on Thursday, December 19, 2013 8:24 PM

 Hmm, now this makes me want to get out my other Baldwin, the one without sound, it has a T1 in it, and while I replaced the factory yellow LEDs with golden-white, all I did was bend the leads of the new LEDs to match the patter of the old ones, and put them in place - still contacting the strips off the factory board, thus using whatever factory electronics are there. I don't recall mine visibly blining when dimmed, and I think I actually set that one to reverse dim and dim when stopped, which is not correct after I found an employee rulebook, so I will change it.

             --Randy

 


Modeling the Reading Railroad in the 1950's

 

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

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Posted by tstage on Friday, December 20, 2013 9:10 AM

That's exactly what I did, Randy.  I replaced the LEDs with Yeloglo LEDs and used the copper strips that are on the light board to make contact with the LEDs.

So, what is the proper lighting effect for a Baldwin VO-660?  Is it also the same for a VO-1000?

Tom

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Posted by rrinker on Friday, December 20, 2013 10:45 AM

 Well, proper lighting can vary by railroad. Typically it's found under Rule 17 (some rule numbers/letters are standardised) which is why the effect for opposite dim and dim when stopped  is usually called "Rule 17" lighting on decoders. But the rules have evolved over time, in fact I have to check but it will actually depend on exactly which year I pick to be my modeled year, because right around the time I model, they changed from not turning on headlights at all during the day to having them on. Some switcher rules were exactly what I set, other times it was dim always, or no lights in daylight, or always bright both directions, etc. The other thing is the the dim when stopped aspect usually applies only when there is an oncoming train (kinda like cars, no bright lights int he face of the oncoming driver).  ALl the automatic stuff really is unrealistic, real locos don;t automatically change the lights, if you've seen cab pics, there are usually two knobs, one for the front light and one for the back light, with off-dim-on settings. Want to reverse the headlights? Turn the front one to off, turnt he rear one to on. Doesn;t happen just because the reverser handle was moved. Most decoders off that as an option, sucks up a total of 4 function keys though, 1 each for the on/off and 1 each for the bright/dim, for totally independent control of the lights per prototype. Then you cna randomly have an officer catch some engineer not following the rules and issue demerits.

           --Randy

 


Modeling the Reading Railroad in the 1950's

 

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

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Posted by rrinker on Friday, December 20, 2013 6:01 PM

 Checked the rulebook, yard switchers are covered in Rule 18, not Rule 17. Yard switchers will show a light front and year by night. A white light will be used in the event there is no rear headlight. The light against coupled cars may be extinguished. Nothing about dimming or anything.

                 --Randy

 


Modeling the Reading Railroad in the 1950's

 

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

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Posted by wjstix on Tuesday, December 24, 2013 8:36 AM

I'm assuming you double-checked that the CV that controls the setting for like Mars lights / Gyra lights isn't set to a value that would cause the light to flicker or pulse under certain situations??

Stix

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