Anyone have recommendations on how to get a dimmer ditch lights or just have ditch lights turn off for flashing with a Digitrax decoder? I have several Digitrax DN613K1C decoders and have recently hooked up independent ditch lights in the locos with LEDs. I was able to program the decoders to have the ditch lights flash alternatively when F2 is pressed. Unfortunately the difference between the on and dim/off state isn't as noticeable as I would like. From what I have read online it seems like there isn't a good way to do this with LEDs (CV 62 adjust brightness for incandecant lights but it is recommended to keep it at the minimum of 0 for LEDs). Only thing I can think of trying is just to put a big block of resistance in to see if that helps dim them down. But my concern is that would also dim the top end brightness and so the difference in brightness would just remain the same.
Would you consider painting them? I used to have some transparent Tamiya paint, orange and yellow, that dimmed LEDs. I looked to see if I still had any to get you a P/N, but no luck. Another place to try is Evan Designs website, they sell LEDs, but somewhere on the site they offer advice on dimming LEDs with paint, acrylics I think. Good luck.
Thanks Seep K l. I am trying to just adjust the dim setting when they flash. I want a bigger difference between the Would the paint make the bright setting dimmer too?
What value resistor are you currently using? Increasing the resistance is certainly something to try. It will dim the top end brightness as well; however, perceived brightness is not a linear response to the actual brightness, and the brighter a light is the lesser the response to changes. This means you will likely percieve a greater reduction in brightness at the low end and a greater difference between high and low.
That actually sounds pretty large to me, but with modern high efficiency LEDs, maybe not. It certainly won't hurt to try a higher resistance.
The issue is the Digitrax decoder. It's made to work with incandescent bulbs (hooray for old tech, lol), which would give you the effect you're looking for. I have a Digitrax sound decoder in one of my Kato P42s and it behaves exactly that way - the dimming is too subtle to be noticeable. If you want flashing ditchlights that work well with LEDs, use a TCS or an ESU decoder instead. Most TCS decoders have individual onboard resistors for most of the outputs, and ESU decoders have at least 2 onboard resistors.
I forgot to mention that Digitrax decoders do have a CV for selecting lamps or LEDs. make sure CV61 is 0 (or 2 if using Transponding). The default shouhld be 0, but it's definitely something to check.
I did have one series 7 decoder which I was surprised to learn did have current limiting resistors for LED (after I had already put in my LED + resistor. But still had the same issue with the brightness. Maybe once they get series 12. I have a few ESU decoders in other locos and love the flexibility with the function set up. Unfortunately these locos had their decoders installed when I just needed motor control and wasn't into the lighting set up.
ESU doesn't seem to have a lot of 'drop-in' non-sound decoders but one can always install a wired one where a 'drop-in' from another manufacture would go. Once one has done a couple wired ones they don't take that much more time to do vs. a 'drop-in' and are less expensive to boot. I really like ESU's ESU 59820 LokPilot 5 Micro NMRA DCC Decoder - NEM652 8-pin Wired Plug (cut the plug/connector off). You can find these from multiple sources for about $30. They have 4 amplified outputs in addition to the forward and rear light ouTputs and 2 more that are logic outputs but can be changed with a cheap add-on board to be also amplified outputs, so lots of lighting control. They are also super small and will fit into anything. They are only a couple dollars more than a wired decoder from others that only have maybe 3 total function outputs and less than any of the drop-in decoders from Digitrax or TCS. On trying the resistor I'd jump to a 2K one and then either work up or down. I've run 2K on 5v circuits with 0402 LED's (small) and they are still way bright and with the decoder they are getting at least 12 volts. I think you will be surprised how high a value you can go to and still have a bright light. Sumner
The ESU LokPilot decoder manual recommends between 470 ohms and 2.2K ohms series resistance for LEDs. Different color LEDs have different forward voltage across them, and therefore different series resistor values to drop to that voltage at a given current. Your mileage may vary; objects in mirror are closer than they appear; closed course, professional driver; do not look into the laser with your other eye.
I tried adding another 4k of resistance to one of the ditch lights tonight. That brought the total resistance up to 5k. Didn't make a noticeable difference in either the bright or dim levels. Next time I stop by the hobby shop I'll have to see if they have the Tamiya X-19 Smoke. I think that is the translucent paint that Sepp K was talking about.
I find it hard to believe adding 4k wouldn't be noticeable. Are you sure you added the resistor correctly? You did add it in series, not parallel, right?
Do you have a simple wiring diagram of the wiring now? Also if you put a 10k in and it is the same there is something else going on. Sumner
Here is is what it looks like for the ditch light I modified. The circle thing at the bottom represents the decoder.
Do you have a manufacturer and part number for the LED? I'd be interested in seeing the specs for it.
Is that output a controlled current output, rather than a voltage output? The former would be immune to excess resistance (up to a point). Just thinkin' out loud...
