Re: HO Headlight Suggestions?

My trick in this regard is to use a very small bulb and a MV lens to focus the light a bit. I usually get a beam that is about 2' diameter about 10' away from the loco when things are adjusted right in the headlight shell. I also leave the bulb glowing yellow at about the color of a kerosene flame as this tends to be what a low beam on the loco looks like.

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works evevery time it is tried!

To get a beam, you need to focus the light with a lens or parabolic reflector.

There have been some 'grain of wheat' sized lamps made with an integral lens in the top of the bulb. These did produce a beam of sorts, but it rarely was directed right out of the end or the bulb, but rather at some unpredictable angle. To direct the beam in front of the loco, you had to mount the lamp at some strange angle (different for every individual lamp). They COULD look nice, though.

Unfortunately none of the smaller mini lamps I have found have such a lens. I suppose you could use a separate lens, but finding a suitable one would be a task. You'd need a VERY short focal length, perhaps 1/4" or less, and a diameter to match your headlight housing. Not a common lens at all.

One problem is that to get a well focused beam you need a 'point source' light. No such lamp exists. In many model RR lamps the filament size is a large fraction of the aperture. The filaments are nowhere NEAR 1/87 (HO scale) of a protype filament, but are much larger and 'out of scale'. That means that even with a lens you'd get a rather broad beam, not the 'pencil' beam I think you're looking for.

You'll need the smallest lamp you can get, with an appropriate lens, and perhaps a tiny reflector.

The idea is possible, and certainly has merit, but I don't think it's going to be easy to do really well. It may well be possible to do considerably better than the average 'off the shelf' model, however. Indeed, I've seen THAT done many times. But something approximating the beam of a prototype headlamp, no.

Dan Mitchell ==========

Glen wrote:

Make that 'all white LEDs' and I could go along. Of course white LEDs are all effectively 'newer' compared to the Red and Green ones we have had for many years. And Red, Green Yellow and Blue LEDs don't need tinted casings. But for headlamp purposes the yellow on the standard yellow LED is too yellow and not bright enough.

Keith Make friends in the hobby. Visit Garratt photos for the big steam lovers.

The comment below is wrong. The earliest LED's produced either infra-red of red light. Next came yellow and green versions. These have all been common for many years now. The blue ones came along about ten yeas ago, but were VERY expensive at first. Now they cost little more than the common red/yellow/green ones. Now we have 'white' LED's ... sort of.

Any LED produces a color that is determined by the semiconductor junction properties built into it. Longer wavelength LED's were easier to develop. As the technology progressed, the color progressed down the spectrum toward the blue end. The newer ones available were always the more expensive. Now the common red/yellow/green ones are 'dirt cheap'.

A 'white' LED is just a blue LED with a phosphor-doped plastic housing. The phosphor absorbs some of the high energy blue light and re-emitts at a variety of other frequencies, thus approximating 'white' light. The blue source is always visible to some extent, however thus accounting for the bluish appearance of the light. Using a yellow plastic filters (absorbs) some of the excess blue, thus producing a better color to approximate incandescent lamps.

Dan Mitchell ==========

Frank Eva wrote:

Sorry Bob (And thanks to all for the replies). What is an MV lens?

Glen

Bob May wrote:

MV makes many model sized lenses:

My problem with the new "gold white" LEDs is that they have an EXTREMELY orangish-yellow color, so much so that when turned off they really look like they are a "turned on" with a redish-yellow color.

However, just saw some new ones available at Tony's that say they have a crystal clear color when not on. Has anyone tried these?

I believe it's more than just a colored case and involves the chemical coating inside as well. Jim Hinds worked for months with an LED manufacturer to get it right. It was specifically manufactured for model railroad use.

It doesn't have the intensity of the pure whites, but in most cases that's a good thing.

Mike Tennent "IronPenguin"

I've used the colored LEDs and they have deep coloration in the casing. I believe that this is how the colored light is produced, and why they aren't very bright...

Thanks for the correction - it's obvious that you have a better background in the technology than I do - all I have to call upon is my experience using the latest releases of LEDs that are targetted at model railroaders. And in every instance, I have found that the colored LEDs use "doped" casings that filter the blue light out, while cutting down the overall brightness in the process. Even the Golden Whites by Richmond Controls have an amber-colored casing, and the light output is noticeably weaker than a white LED.

I want to see a golden white with NO color in the casing. Now, that would be great!

Not in certain installations - specifically those headlamps that use a long plastic diffuser to run between the lamp and the light source. You need every candle in those instances, and golden white LEDs don't seem much better than incandescents.

Has anyone tried painting the bulb silver (like bunper chrome, very shiny). Pant all around except for the tip. That is the way spot lights are made, except not painted on outside, but the idea may work. ED

Nope. The colored light is produced that way by the semiconductor junction. It is also a very 'pure' color, with a very narrow spectral range. All the usual colors are available in clear cases, though most common ones often have plastic cases colored to match their emission color. That makes them easy to identify even when not illuminated. A red LED will be red regardless of the color plastic case that surrounds it.

Since the plastic can only absorb light, it will be only clear, or the same color as the LED. that is, say a red LED will have either a clear or red case. The red plastic will transmit the red light almost as well as a clear case. Ditto for the other colors, respectively.

You will never find a red (for example) LED with a green case since the green plastic would absorb almost all the red light, and nothing much could be transmitted to the outside. Ditto for the other colors. A clear case will work with any LED color, but they all look alike when 'off'.

The so called "white' LEDs are a different 'animal', they are basically BLUE LEDs, but their plastic contains a phosphor that (re)emits light when 'excited' by the blue light from the LED. This greatly broadens their spectrum, approximating white. So, in a 'white' led the case is actually part of the emission system.

Dan Mitchell ==========

Frank Eva wrote:

Correct observation. The color shifts in the white LEDs are caused by filtering ... that is absorbing unwanted colors. Filtering cannot create a new color ... just remove unwanted color. For ANY color to pass through a filter, it must have existed in the light before it was filtered.

And even the best filters absorb SOME of all colors, meaning that they dim all light somewhat, just some more than others. So, yes, a filtered light source will always be dimmer than an unfiltered source.

Dan Mitchell ==========

Frank Eva wrote:

The thing I like about the lenses is that you can remove the foil back of the lens and have a real nice short focal length lens. I've used them in a number of locos with a microlamp at the back of the headlight and get a nice beam out of the assy.

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works evevery time it is tried!

Not the actual LED, but I have tried painting clear plastic diffusers in P2K locos a flat black, when I'm installing an LED, and I have found that this actually makes things worse!

Then why can't Richmond Controls produce a Golden White without coloring the case?

That has not been my experience - the colored LEDs sold to model railroaders are simply too dim to be used in headlamps. I've tried yellow, and it's even dimmer than a low-voltage incandescent!

Frank Eva Digital Railroader

I must have missed the first part of this thread - can you explain which lenses are you referring to, and what exactly is a "microlamp"?

Frank Eva Digital Railroader

Light pipes used by P2K and others need reflective sides. If you paint them black, some of the light is absorbed there. I wrapped some in silver colored reflective metal tape which worked nicely. A gloss silver paint would be OK, too.

I have painted the sides and backs of LEDs black to prevent ligth leakage and that works OK.

Ed

in article 6%oGb.187078$ snipped-for-privacy@twister.rdc-kc.rr.com, Frank Eva at snipped-for-privacy@wi.rr.com wrote on 12/24/03 3:07 PM: