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Headlight Dimming?

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Headlight Dimming?
Posted by wobblinwheel on Thursday, November 09, 2017 3:12 PM

I just installed a Digitrax decoder (DN136PS) into an old Proto 2000 E6 loco. The LED I installed is really bright, and according to the downloaded info from Digitrax, I can enter a value of 8 into cv49 (forward headlight, white wire) for "Rule 17 dimmable headlight when F4 is activated". I can't get it to work, doesn't have any effect. Everything else works perfectly. Any ideas? The loco reacts to the setting when I enter the value, but no change. Any suggestions would be appreciated!

Mike C.

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Posted by tstage on Thursday, November 09, 2017 3:19 PM

Mike,

Try lifting the locomotive from the programming track and resetting it back down again.  Sometimes CV changes don't "stick" until you interupt power to the locomotive.

Tom

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Posted by wobblinwheel on Thursday, November 09, 2017 3:36 PM

Thanks, I'll try that and let you know...! I bought a 100-pack of "warm whte" led's from Amazon, and they are BLINDING! Look good, but BRIGHT...

 

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Posted by tstage on Thursday, November 09, 2017 3:57 PM

Mike,

Gotta ask: You did install a resistor for your LED, yes?

Also, I don't know about Digitrax but most decoders will allow you to adjust the headlight brightness.  For a TCS decoder it's CV64 and the default value is "15" for incandescent lighting.  The value range for incandescent lighting is 12-18 and an LED, 2-6.  See what the value is for CV64 and drop it down a couple of notches to see what that does.  Worth a try...

Tom

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Posted by wobblinwheel on Thursday, November 09, 2017 4:15 PM

Yeah, if I remember corectly, Digitrax recommends 680 ohm resistors....anyway, whatever they recommended, I used. I experimented with some resistors I already had, but after blowing a few led's, I went ahead and ordered the ones they said use. I can run led's right off the track power, if I want to, without issue. I've got 97 led's and 250 resistors.....I'm gonna light up EVERYTHING...!

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Posted by tstage on Thursday, November 09, 2017 4:20 PM

I normally use 1K ohm resistors.  Even then it's still pretty bright.  I would try changing CV64 to see if that helps.  Couldn't hurt...

Tom

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Posted by rrinker on Thursday, November 09, 2017 4:33 PM

 Add another resistor. You don't want to rely on the Rule 17 dimming to keep the headlight at a 'normal' brightness all the time.

CV62 controls the dimming effect for lamps and LEDs. You want to set it at something like 4 for use with LEDs (anything less than 16 - values 0-15 controls the blink rate for flashing functions).

                                  --Randy

 

 


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Posted by wjstix on Thursday, November 09, 2017 4:57 PM

Re Rule 17 dimming, most decoders that have that have a CV to set the full brightness and a CV to set the dimmed brightness. You might want to check what you have in both CVs.

 I had an engine with LED headlights that I thought wasn't working right because the headlights wouldn't dim. Turned out the CV for the dimmed light level was too close to the level for the bright light level. Adjusting the dimmed light CV down made the change to dim light noticeable.

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Posted by tstage on Thursday, November 09, 2017 6:39 PM

rrinker
CV62 controls the dimming effect for lamps and LEDs. You want to set it at something like 4 for use with LEDs (anything less than 16 - values 0-15 controls the blink rate for flashing functions).

Randy,

So is it a different CV for Digitrax decoders than it is for a TCS decoder?

Tom

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Posted by rrinker on Thursday, November 09, 2017 6:48 PM

 Yes, CV64 is undefined on Digitrax. CV62 has the setting to adjust between light bulbs and LEDs.

LEDs don't dim the same way a light bulb does, what would dim a light bulb would still light an LED to almost full brightness, hence a different setting to achieve a 'dim' vs 'full brightness' Most decoders these days are set for LEDs, but it seems Digitrax still default to incandescent bulbs and allows you to adjust for LEDs. 

                                 --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 Thursday, November 09, 2017 6:59 PM

Same with TCS, Randy.  As mentioned earlier, the default value for CV64 is "15" (mid-range for incandescent - i.e. 12-18) but 2-6 is the range for LEDs.

Tom

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Posted by wobblinwheel on Thursday, November 09, 2017 8:50 PM

I have tried a few things...First, after setting cv49 to 8, cutting power to the loco did not make a change, however, after reading more info, I entered 104 into cv49 to enable "Rule 17 dimming in reverse" (no reverse lights on this loco) and the headlamp dimmed in reverse AND F4 will dim the headlight! I don't think I really care that the headlamp no longer turns off in reverse. One of the main reasons I want to dim the headlamp is because it sort of "drowns out" the Mars light above it. I put a regular "white (blue-ish)" led in Mars hole because I liked the contrast between the two, so I only really want to dim the headlamp only, not the Mars. CV 62 is already on 0 for the fastest Mars light speed (default-according to the manual). F4 now helps a fair amount, but it stays on in reverse, which is ok, I think....manual still says, no matter how many times I read it, that setting CV49 to 8 will enable F4 headlamp (only) dimming, but it still won't work that way. I still haven't read where they came up with "104" to dim in reverse...? From what I have read about CV62 is it controls the flashing rate of different effects, AND the holdover time for lights when a "keep alive" capacitor is installed (which I don't have...or need)...EDIT: the 104 entered into cv49 has something to do with turning-off or dimming Ditch Lights while in reverse. I can only figure it involves "special logic for ditch lights" =96, and Rule 17 dimming =8 =104. Since I don't have ditch lights, I assume I would enter only "8", but that won't work...EDIT AGAIN: Cv 61 sets the "Lighting Algorithm" for LED's. Set to 0 (default-LED)

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Posted by hobo9941 on Thursday, November 09, 2017 11:22 PM

 The LED I installed is really bright

You might also try a larger resistor. If the LED is really bright, the decoder may be dimming it but not enough to notice. If the LED is running at maximum brightness, a slight reduction in voltage or current might still leave it at full brightness.

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Posted by tstage on Thursday, November 09, 2017 11:32 PM

wobblinwheel
...I entered 104 into cv49 to enable "Rule 17 dimming in reverse" (no reverse lights on this loco) and the headlamp dimmed in reverse AND F4 will dim the headlight! I don't think I really care that the headlamp no longer turns off in reverse.

Mike,

If Rule 17 lighting is working properly then the front headlight will go dim when stopped and when traveling in reverse but it should never go out.  Only the headlight in the direction of travel should be a "full strength".

As others suggested, I would try a higher resistor value (perhaps 2K or >) to reduce the intensity of the headlight.

Tom

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Posted by wobblinwheel on Thursday, November 09, 2017 11:48 PM

I think I'll try adding another 680 ohm resistor because I have hundreds of them. Now tell me, do I run them in series or side-by-side (parallel?)

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Posted by tstage on Friday, November 10, 2017 12:30 AM

In series.  Resistance values add that way.  You can also trim the resistor wires short to save space.

Tom

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Posted by wobblinwheel on Friday, November 10, 2017 1:09 AM

Yeah, I figured it would be series. Surely the best way to dim the headlamp and not the Mars light. The Mars light just looks cool even running by itself! I have tons of space under the shell, won't be a problem. Actually, it's not so bad, now that I can dim it a bit with F4, and full bright is tollerable during the day, but not under low lighting, it can give you a headache if you look at it too many times. When I get up the nerve to wrestle the shell off again (the hardest part), I'll add another resistor or two. I'll let you know...Thanks, guys for all your input...!!

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Posted by hobo9941 on Monday, November 20, 2017 8:40 PM

Resistors in series add resistance.

Resistors in parallel reduce resistance!

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