The Color of Atlas LEDs

[haasmarc]

I don't know if it bothers any body else but I spent several hours changing out the smd leds on the latest Trainmasters, SD50's and U23b's to golden white.  I really don't like the yellow leds they are putting on some of the releases.  The FA1's, SD45's and RS3/RSD4/5's look fine.  I asked the Atlas guys at Amhearst last January and they said no one complained.  Maybe I am just too picky but I definitely don't care for the yellow.  I also leave a short length of wire on the Trainmaster short hood led so it is closer to the light pipe and therefore has the same brightness level as the one on the long hood.  Yellow on the left, replacement on the right.



I could see them being different on the SD45's since they are Soundtraxx instead of ESU, but it seems to be a coin flip on the latest ESU's which color it will be.

[tehachapifan]

Point of clarification, the Atlas N scale SD45's have their own light board that the decoder plugs into. Same LED and color whether you use an ESU or Soundtraxx decoder.

[Mark5]

100% agree on the left unit. Pre-halogen lights were yellowish, but really?

[GM50 4164]

Marc, I hate the new yellow or amber LEDs that are coming on the newer boards Atlas is using. I've purchased some replacement 0402's to maybe swap out myself one day! Would you mind sharing a link to the LED's you went with and a photo of your work? I got mine from Digikey and I'm hoping they'll be a even swap.

[haasmarc]

Benjamin,

These are the ones I am using.  They are 0603's.

https://www.ebay.com/itm/253170046625

I will post a pic later when I get a chance.

[wmcbride]

I agree that these new yellow LEDs are not great.

They are also using them on their HO engines. I bought a recent GP40 for my switching layout and the ditch lights and headlights are just way too yellow and need to be replaced.

[davefoxx]

I agree that these new yellow LEDs are not great.

They are also using them on their HO engines. I bought a recent GP40 for my switching layout and the ditch lights and headlights are just way too yellow and need to be replaced.

Yep, I’ve been replacing the yellow LEDs in my HO scale fleet with golden white LEDs.  I did a batch of U36Bs and B30-7s not too long ago.  On the left is “before,” and on the right is “after,” which not only improved the color but increased the luminosity to something more prototypical:



DFF

[Ed Kapuscinski]

Ugh, yeah. The yellow LEDs in my V&O SD9 suck. I don't want to mess with them though, but it is a disappointment after seeing much better LEDs being used by a bunch of manufacturers lately.

[jagged ben]

Are we seriously going back to the 90s here?

[peteski]

Are we seriously going back to the 90s here?

Neah, I doubt it.
When manufacturers started replacing incandescent bulbs with LEDs, I think Kato  was the first company to do that.  They used standard lemon-yellow LEDs.  Then other manufacturers did the same and they all used a variant of standard yellow LEDs. Shade of yellow varied slightly, but they were all typical yellow LEDs where the actual LED die encased in the epoxy case produces the specific color of light.

At that time the white (and blue) LEDs were still in their infancy. Today the white LEDs utilized for most consumer equipment are based on blue LED die encased in a phosphor coating. That phosphor coating converts portion of the blue light emitted by the blue LED die to a wider spectrum light, mostly in the yellow/amber region, but some of the blue light still passes through the phosphor coating.  The blend of all those colors appears as white to the human eye.  The actual color temperature of the white light depends on the blend of chemicals  in the phosphor coating and by percentage of the blue light which passes unconverted.  Because of that there is a range of whites produced by LEDs.  That is where the color temperature comes in.  For example white LED producing 2600K temperature light simulates the warm white of an incandescent bulb.  A 3000K LED produces light with less of the yellow/orange tones which is similar to a typical halogen light, and 5000K or higher temperature LED (where a lot of the blue light passes through the phosphor) produces cool (bluish) white.

The small SMD LEDs Atlas uses are likely those blue die+phosphor white LEDs usually used for model headlights, but their phosphor blend produces less orange and more yellow light, resulting in a yellowish white. These LEDs are not anything like the origina yellow LEDs used in the 90s.

Because only relatively small amount of phosphor surrounds the blue die in small SMD size LEDs, a lot of the blue light passes through,so it is difficult to get a really good 2600-3000K light,  especially when the LED is mounted in a way where the light is coming from one of its sides (not from the top).  I have tried a wide range of white SMD size LEDs (from 0402 to 0805 sizes), including warm, and "sunny" LEDs from Richmond Controls, N-gineering, , and bunch of "warm" from eBay, and none produce light which to me would be a good representation of a typical locomotive headlight.  Some come close, but not great.  The best representation of a "headligth white" light I have found all came from non-SMD standard 3mm LEDs that Atlas and Kato used.  Miniatronics also sold similar LEDs (Not sure of they still do).

[haasmarc]

Would you mind sharing a link to the LED's you went with and a photo of your work?

Benjamin,

Here are picks of both ends on the Trainmasters.

Moving the led forward closer to the light pipe helped make the light intensity the same for both ends.

[tehachapifan]

On a side note, I'm not really thrilled with this increasing trend of using those super tiny LEDs on lightboards or decoders (as seen above). Unless there is no other solution due to a shell clearance issue, an even slightly larger LED would work so much better. Some of these LEDs or so tiny you could lose them under your fingernail!

[GM50 4164]

Benjamin,

Here are picks of both ends on the Trainmasters.

Moving the led forward closer to the light pipe helped make the light intensity the same for both ends.

Thanks for the photos Marc. This is pretty much what I'm planning on doing once I have my work station set back up.