LEDs for Z-Scale Searchlight Signals

[ednadolski]

Just thought I would revisit this to add some (surely OTW) speculation.  Has anyone ever tried using fibre optics to build searchlight signals in Z scale?  This stuff seems to be available as small as 0.5mm and 0.25mm diameter.  The main idea is to locate the RYG LED below, and route the FO strand up the hollow-wall tubing to the signal head/lens.  The top end of the FO would terminate at a 'lens' formed by heating the end of the strand with a soldering iron or such (never tried that myself, but I seem to recall it has been done by some clever/creative folks).

One challenge would probably be how to make a 90-degree 'bend' at the signal head.  Perhaps the FO could be heat-formed into a small radius, or the signal head itself could be 3D printed from clear resin to act as a light guide, and painted (except for the 'lens') with something opaque like say TCP Aluminum to contain the light.

Anyways, just thinking out loud, FWIW....

Ed

[peteski]

As I see it, with a sharp 90 degree bend, there will be quite a bit of light loss a the bend. Fiber optics work best with larger radius bends.  The other possible issue is the amount of light that can be emitted from such a small diameter fiber. maybe it would be acceptable if a very strong light source was used.  In my experience you can heat up and  "mushroom" plastic fiber optics, but even then, the light is still emitted from the center part of the mushroomed area.

The other issue is aiming the fiber at the source of light.  The RYG LED actually contains 3 individual LED dies.  To maximize the amount of light entering the fiber, it needs to be placed directly over the light source and as close as possible.  With such small diameter fiber optic, It will not sit directly over all 3 color LED dies.

This is all theoretical, but it would be worth experimenting with. 

[C855B]

When I built my first crude model of a searchlight signal (S scale, when I was 10), I used a piece of mirror in the head to reflect the light from the GOW bulbs at the other end of the brass tube.

Obviously that exact technique couldn't be used in something with any scale fidelity, but the idea can be - fiber optic up the mast with S-curve out of the tubing simulating the conduit to the bottom of the case, terminating vertically, with bit of Mylar or other mirrored plastic in the head to redirect 90°.

[ednadolski]

Interesting ideas... Is there such an animal as rigid fiber optics?  That could be used perhaps to make the mast portion.  For a reflector, it looks like there are some spray paints that when applied to the back side of a clear surface supposedly produce a mirror-like finish.

Thinking about it tho, I guess it could work for a mast with one signal head, but two or more seems problematic.

Ed

[peteski]

Most fiber optics used for communication are actually made of glass, but being so thin, they are actually flexible.  Those will also shatter easily when stressed.  Thicker fiber optics made from plastic are stiffer than the thin ones, but they would likely still be too flexible for a mast.



Not sure if you are old enough to remember these fiber optic lamps from the '70s. I owned one. These used very thin glass optical fibers, and yes the fibers would break if one wasn't careful.

[ednadolski]

Seems there are also plastic fiber optic cables which are more amenable to bending/flexing:  https://en.wikipedia.org/wiki/Plastic_optical_fiber

Looks like there may be some kind of 304 SS capillary tubing with an ID of 0.5mm,  possibly those could take two strands of the 0.25mm FO.   A 6" diameter mast scales to about 0.7mm in Z, so perhaps something close could be done with that.  I guess now i will have to try it out

FO link: https://www.amazon.com/gp/product/B07Y1NMX4H/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1


Another crazy thought -- perhaps one of those small laser pointers could be used as a light source, if it could be found in the correct colors.

Ed

[peteski]

Sure, plastic fibers are much more resilient to flexing. They sort of remind me of fishing line (of course different material and they have a core and outer cladding to keep the lightwaves contained.

Laser light source is an interesting idea, but I have not seen yellow laser pointers.  Green and red - yes.  But maybe like with bi-color LEDs, combining red and green light night result in yellow.  But that would be rather bulky assembly under each signal mast.

[C855B]

... Laser light source is an interesting idea, but I have not seen yellow laser pointers.  Green and red - yes.  But maybe like with bi-color LEDs, combining red and green light night result in yellow. ...

My long-ago, long-forgotten physics studies involving lasers tells me "no" on this idea. The thing that's the different with laser sources is beam coherence - it's what keeps the beam from spreading like a flashlight. Coherence is going to work against convergence, the thing you need to blend colors. I could be off-base here (there are real physicists on this forum), but until corrected, that's my story.

[peteski]

My long-ago, long-forgotten physics studies involving lasers tells me "no" on this idea. The thing that's the different with laser sources is beam coherence - it's what keeps the beam from spreading like a flashlight. Coherence is going to work against convergence, the thing you need to blend colors. I could be off-base here (there are real physicists on this forum), but until corrected, that's my story.

That makes sense Mike - I was just shooting from the hip.  With red and green lasers emitting at the same time you would probably see separate color beams (unless maybe a diffuser (like piece of frosted clear plastic) was used.  At least that is what you will see with your remaining eye. 

[Dwight in Toronto]

That laser warning label made me LOL!

Hey Pete … I’m kinda missing the B&W avatar.  I recently learned that DKS had created all those caricatures for the select few, and I admire the handiwork.   I imagine that opting to change it after all this time must not have been easy.

[JeffB]

That laser warning label made me LOL!

Having been in the industrial laser industry for 30yrs prior to retiring in July, that label is the running joke amongst us laser geeks...  It's a bit shortened from a T-shirt I used to have that said, "Do not look into laser with remaining good eye".

Luckily, I escaped any permanent eye damage, suffering only a few laser burns over the span of 30yrs (most of which were due to someone else's negligence!).

Jeff

[Dwight in Toronto]

Several years ago, I suffered a detached retina and underwent a number of procedures to save/recover some vision in my left eye. 

Knowing how dangerous a laser in the eye can be, it’s a bit ironic that one of the steps in my ordeal was laser fusing of the retinal fragments.  I likened it to arc welding! 

That particular procedure generated more discomfort than any of the needles-in-the-eye treatments that I had endured over the preceding weeks.  I still shudder at the memory of those nerve-jarring laser-pulsing sensations.

[peteski]

That laser warning label made me LOL!

Hey Pete … I’m kinda missing the B&W avatar.  I recently learned that DKS had created all those caricatures for the select few, and I admire the handiwork.   I imagine that opting to change it after all this time must not have been easy.

Actually my current color avatar (with Warhol-like flavor) is the 1st one DKS created for me when he as on his TRW members artistic streak (along with few "Peteski" banner images).  I decided to go back to it.  I actually favor the lively colors to the B/W caricature.  I think I'm the only one that DKS immortalized in color. 

[GGNInNScale]

For n scale signal lights I use either 0201 or 0402 SMD LEDs.  I wire them with either leftover wires from decoders, or single strands of 20ga stranded wire, taken apart to make a bunch of single strands.  Usually, I put a 2.2kOhm or 3.3kOhm SMD resistor in series to limit the current in the LED.  I run the LEDs off a 5V source.  The assemblies are surprisingly rugged, too.  I use the same approach for lighting diesels.  The picture shows 0402 LED with an SMD resistor.

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[carlso]

I am not using these for signal lighting but rather in my project to add step safety lights, truck lights, and ditch lights to my KATO SD-90. Just wanted to show the size of the 0201 LED compared to an old fashioned straight pin head and my pointed tweezers.


I have 8 of these mounted via LokSound5 DCC micro decoder and I have used 1.8K resistors.