LED Brakelights
Bob Edwards
Has anyone here had any experience wiring and building their own custom LED
brakelights? It's a '94 Dodge Spirit, so it's a 12 volt system. I can't
find any LED's that are 12 volt, so I guess I'll have to put in some kind of
resistor for a lower voltage lamp. Also, any recommendations on how to
actually set up a dozen or two LED's in the lens? (I would like to keep the
same lens, but replace the insides) I know that there are screw-in
replacements for the standard incandescant bulbs, but (I know, I'm crazy) I
would really like to learn how it is done and build my own setup.
Thanks,
Jeff
ME Incorporated
of goodies for your project, at least electrically speaking. Sure, there
are other places to buy the stuff, but the Rat Shack has these booklets that
can teach you in easy projects how to make a "bank" of LEDs. You'll learn
on how to make the LEDs work with 12 volts, and how to use them in multiple
setups and also how to wire them up to blink and sequence and such. You
might also find other electrical places that have little projects.
Electronic Parts Outlet in Houston is one such place where anything such as
this can be found on the walls.
It's not terribly hard, though. Each LED has a voltage it works with, and
polarity, and amperage and watts and such. If you pair up two LEDs in
parallel, you halve the voltage, or something like that. Series, you double
it. And so on. All very straightforward, once you get it, but I've slept
many moons since then. But I absolutely remember using a 12 volt
transformer with one of their projects, and made little blinky light setups
for use with a model of the Enterprise. Never did put it in the model, but
it is possible, and these booklets can show you this.
Good luck!
"Bob Edwards" <dolo...@home.com> wrote in message
news:dXgM7.51407$RI2.27302329@news2...
Daniel Stern Lighting
This is a much more complicated and "involved" project than you might
think. LED signalling lamps (brake, tail, turn...) are appearing on cars,
and are widely used on trucks, but it really is not a "retrofit" item in
the sense you're thinking of. The rear lamps of your '94 Spirit -- and
the vast majority of cars on the road as well -- rely on a point source of
light (glowing filament), collecting that light with a parabolic reflector
and dispersing it with pillow optics in the lens. An LED is a vastly
different *kind* of light source. Unlike a glowing filament, it does not
produce light in an even sphere. Instead, it projects a very narrow beam
of light in ONE direction. That's why these so-called "LED retrofits"
consisting of a 1" diameter matrix of LEDs on a bayonet or wedge base are
unsafe; there's no way you can get enough light through a wide enough
angle (horizontally and vertically) to create a safe and legally-compliant
lamp. There are other considerations, too -- it is tricky to get the
right ratio of bright-to-dim intensities both on axis (straight behind the
lamp) and also through the entire vertical and horizontal beam spread.
Look at the optics of the Cadillac DeVille that has Hewlett-Packard LED
tail/brake lamps, or the high-end Mercedes S-class that has LED brake
lamps. You'll see some *very* fancy optics used to coordinate the light
from a *LOT* of LEDs to get everything right in terms of brightness in
both dim and bright mode, uniformity of brightness throughout the
visibility angles required by law, ratio of intensity between "bright" and
"dim" mode, etc. These kinds of optics are not something you can kludge
in your garage, and putting "a dozen or two LEDs" behind your current lens
certainly won't get the job done.
In addition to all of the above reasons why you really could not come up
with something acceptable from a safety performance point of view on your
own, note that you'd be reinventing the wheel. If you have your heart set
on LED rear lamps in your '94 Spirit, you'll be pleased to know that the
size and shape of the reflector would lend itself to a very easy and
properly-performing retrofit using off-the-shelf parts. A Truck-Lite
model 45 LED tail/stop module is about the size of the reflector. You
could simply saw-off the back of the reflector (on a spare pair of rear
lamps...) and carefully glue a Type 45 module in place. Visit
www.trucklite.com for a closer look.
Do-it-yourself projects are fun, but remember you're working with safety
systems everyone else on the road relies upon.
DS
Steve
>On Mon, 26 Nov 2001, Bob Edwards wrote:
>
>>Has anyone here had any experience wiring and building their own
>>custom LED brakelights? It's a '94 Dodge Spirit, so it's a 12 volt
>>system. I can't find any LED's that are 12 volt, so I guess I'll have
>>to put in some kind of resistor for a lower voltage lamp. Also, any
>>recommendations on how to actually set up a dozen or two LED's in the
>>lens? (I would like to keep the same lens, but replace the insides)
>>I know that there are screw-in replacements for the standard
>>incandescant bulbs, but (I know, I'm crazy) I would really like to
>>learn how it is done and build my own setup.
>>
>
>This is a much more complicated and "involved" project than you might
>think.
>
Or *maybe* not.... if you have the right configuration taillamps to
start with.
> LED signalling lamps (brake, tail, turn...) are appearing on cars,
>and are widely used on trucks, but it really is not a "retrofit" item in
>the sense you're thinking of. The rear lamps of your '94 Spirit -- and
>the vast majority of cars on the road as well -- rely on a point source of
>light (glowing filament), collecting that light with a parabolic reflector
>and dispersing it with pillow optics in the lens. An LED is a vastly
>different *kind* of light source. Unlike a glowing filament, it does not
>produce light in an even sphere. Instead, it projects a very narrow beam
>of light in ONE direction. That's why these so-called "LED retrofits"
>consisting of a 1" diameter matrix of LEDs on a bayonet or wedge base are
>unsafe; there's no way you can get enough light through a wide enough
>angle (horizontally and vertically) to create a safe and legally-compliant
>lamp.
>
I agree 100% on all of the above. What is essential is to abandon the
notion that you can directly replace the bulb, socket and all, with a
small array of LEDs, or that you can use cheap LEDS. The necessary ones
are still pretty pricey. Basically, the trick is to take an array of
collimated light sources (LEDs) and place the array in a plaine in the
taillamp optics where the light from the original incandescent bulb had
already been converted to a collimated equivalent source by the
reflector. The new setup wouldn't rely on the reflector at all. Its
been on my back burner to cook up such a thing (I just happen to have
two spare sets of rear lamp lenses for my 73 Satellite- I'm a packrat)
and see how it works. If I live long enough, I'll do it and let you
know the results.
>There are other considerations, too -- it is tricky to get the
>right ratio of bright-to-dim intensities both on axis (straight behind the
>lamp) and also through the entire vertical and horizontal beam spread.
>
The ratio at the LEDs is taken care of by one resistor value. Making
sure its consistent both on- and off-axis depends on the approximation
of an array of collimated sources being "equivalent" to a bulb-and
reflector at a distance of about a centimeter behind the pillow lens. If
the approximation is good, then the ratio will be OK. To whatever degree
the approximation fails, the off-axis ratio will fail. The very fact
that LEDs are not truly collimated sources *may* actually help here.
In short, I don't have a simple "recipe" and even if I did, I wouldn't
trust it without much testing, and certainly wouldn't encourage anyone
to try it on a taillamp that I have never seen before.
> A Truck-Lite
>model 45 LED tail/stop module is about the size of the reflector. You
>could simply saw-off the back of the reflector (on a spare pair of rear
>lamps...) and carefully glue a Type 45 module in place. Visit
>www.trucklite.com for a closer look.
>
Well, THATS no fun! Anyone can order from a catalog... ;-)
<as he writes down potential modules to order.....>
Josh Weigner
bulb socket.
Josh
"Bob Edwards" <dolo...@home.com> wrote in message
news:dXgM7.51407$RI2.27302329@news2...
Daniel Stern Lighting
> >>Has anyone here had any experience wiring and building their own
> >>custom LED brakelights? It's a '94 Dodge Spirit
> >This is a much more complicated and "involved" project than you might
> >think.
> Or *maybe* not.... if you have the right configuration taillamps to
> start with.
The only "right configuration" to have a fighting chance at easy and
problem-free LED retrofitment is a taillamp that uses Fresnel optics
(concentric prismatic rings) rather than a parabolic reflector. And even
then, it's not a slamdunk, just a fighting chance. VERY few cars use
Fresnel-optic lamps. Some early '70s Volvos...a few early-70s
Mopars...some old AMC products...
> > LED signalling lamps (brake, tail, turn...) are appearing on cars,
> >and are widely used on trucks, but it really is not a "retrofit" item in
> >the sense you're thinking of. The rear lamps of your '94 Spirit -- and
> >the vast majority of cars on the road as well -- rely on a point source of
> >light (glowing filament), collecting that light with a parabolic reflector
> >and dispersing it with pillow optics in the lens. An LED is a vastly
> >different *kind* of light source. Unlike a glowing filament, it does not
> >produce light in an even sphere. Instead, it projects a very narrow beam
> >of light in ONE direction. That's why these so-called "LED retrofits"
> >consisting of a 1" diameter matrix of LEDs on a bayonet or wedge base are
> >unsafe; there's no way you can get enough light through a wide enough
> >angle (horizontally and vertically) to create a safe and legally-compliant
> >lamp.
> I agree 100% on all of the above. What is essential is to abandon the
> notion that you can directly replace the bulb, socket and all, with a
> small array of LEDs
And yet, you notice it didn't take an hour for some idiot to suggest going
on Ebay and getting exactly this junk. People wonder where my short
temper comes from.
> or that you can use cheap LEDS. The necessary ones
> are still pretty pricey. Basically, the trick is to take an array of
> collimated light sources (LEDs) and place the array in a plaine in the
> taillamp optics where the light from the original incandescent bulb had
> already been converted to a collimated equivalent source by the
> reflector. The new setup wouldn't rely on the reflector at all.
Right. But remember, that still doesn't solve the optics problem. You
would either need a LARGE number of LEDs, VERY closely packed together, or
the aforementioned fancy optics.
> been on my back burner to cook up such a thing (I just happen to have
> two spare sets of rear lamp lenses for my 73 Satellite- I'm a packrat)
> and see how it works. If I live long enough, I'll do it and let you
> know the results.
SL- Contact me at the usual address.
> >There are other considerations, too -- it is tricky to get the
> >right ratio of bright-to-dim intensities both on axis (straight behind the
> >lamp) and also through the entire vertical and horizontal beam spread.
> The ratio at the LEDs is taken care of by one resistor value.
Sure, that's the easy part. The hard part is the ratio as viewed by the
guy who needs to be able to tell RIGHT AWAY whether that's a taillamp or a
brake lamp in front of him...regardless of if he's in your same lane, or
one to the left or to the right, or on a bike on the shoulder, or in a
truck way above the level of your taillamps...
> Making
> sure its consistent both on- and off-axis depends on the approximation
> of an array of collimated sources being "equivalent" to a bulb-and
> reflector at a distance of about a centimeter behind the pillow lens.
But there are additional factors with off-axis refraction. A rough
approximation of this concern is the "bright flash" you see as you cross
through a certain horizontal angle off axis inboard and outboard when
observing the brake/taillamps of the immediate-past-generation Ford
Explorer. There's no backplate on the reflex retroreflector, so it
efficiently bends light from the bulb into a strong beam off axis, and as
you drive through it (or it drives past you) you see a sudden flash of red
that is much brighter than the taillamp. It's easy to mistake it for a
brake lamp. You can even see it as a red X on the pavement about 5 feet
behind such vehicles.
> > A Truck-Lite
> >model 45 LED tail/stop module is about the size of the reflector. You
> >could simply saw-off the back of the reflector (on a spare pair of rear
> >lamps...) and carefully glue a Type 45 module in place. Visit
> >www.trucklite.com for a closer look.
> >
> Well, THATS no fun! Anyone can order from a catalog... ;-)
>
> <as he writes down potential modules to order.....>
The standardised truck signalling lamp formats (4" round, 7" x 3", etc.)
have encouraged the development of many LED models. Cars do not use
standardised formats, so a lamp must be carefully and expensively
developed for each specific model.
DS
Josh Weigner
"Daniel Stern Lighting" <das...@vrx.headlamp.net> wrote in message
news:Pine.SOL.4.33.011126...@alumni.engin.umich.edu...
I guess you're calling me an idiot then? Did i say the stuff was good? no.
Did i say it was safe? no. I just answered his question, so Fuck you.
Viragonut
>> custom LED brakelights
There are actually LED arrays set up to plug into a regular 1157 tail light
bulb socket. It simply twists in like a regular
bulb . We sell them at the bike shop I work at ,$24.95 us .
Daniel Stern Lighting
Do I hear three?
DS
Steve
>
>>I agree 100% on all of the above. What is essential is to abandon the
>>notion that you can directly replace the bulb, socket and all, with a
>>small array of LEDs
>>
>
>And yet, you notice it didn't take an hour for some idiot to suggest going
>on Ebay and getting exactly this junk. People wonder where my short
>temper comes from.
>
Those are the guys who subscribe to Nigel Tufnel logic. ("But this one
goes up to 11.")
>
>Right. But remember, that still doesn't solve the optics problem. You
>would either need a LARGE number of LEDs, VERY closely packed together, or
>the aforementioned fancy optics.
>
That is (maybe was, depending on the cost of the Trucklite option...)
exactly my plan. Standard perfboard would allow you to create adensely
packed array of LEDs. A solid plane of light-emitters. Any less dense
and you *immediately* violate the optics assumption that I described.
>
>
>The standardised truck signalling lamp formats (4" round, 7" x 3", etc.)
>have encouraged the development of many LED models. Cars do not use
>standardised formats, so a lamp must be carefully and expensively
>developed for each specific model.
>
<pulling pin on hand-grenade>
So wouldn't it make sense....
<tossing into room....>
to use a small number (and it could even be as large as a dozen) of
standard lamp formats....
<running away quietly>
for automotive headlamps too, so that we avoid the nightmarish plastic
abortions (but they look so KEWL!) found on so many cars now?
<waiting for the earth-shattering "Kaboom">
:-)
TerryWood
of reflection and you are right in the fact that the LED lights wont produce
enough light, They mught be bright enough, but there is no way you can have
them reflect in more than one direction with out the use a bunch of
reflectors, However, the lamps that this guy is talking about are DOT
approved, so therefore are "safe" enough, but i would recomend themnews:Pine.SOL.4.33.011127...@alumni.engin.umich.edu...
Daniel Stern Lighting
On Wed, 28 Nov 2001, TerryWood wrote:
> i do understand the princibles
> of reflection and you are right in the fact that the LED lights wont produce
> enough light, They mught be bright enough, but there is no way you can have
> them reflect in more than one direction with out the use a bunch of
> reflectors,
True enough.
> However, the lamps that this guy is talking about are DOT
> approved,
No they're not. There's no such thing as "DOT approved". DOT does not
"approve" anything. Items of motor vehicle safety equipment must be
certified BY THEIR MANUFACTURER as complying with all applicable Federal
Motor Vehicle Safety Standards. Aside from that, an LED replacement for a
filament bulb *cannot* meet the relevant SAE Technical Standard.
DS
Daniel Stern Lighting
> >>I agree 100% on all of the above. What is essential is to abandon the
> >>notion that you can directly replace the bulb, socket and all, with a
> >>small array of LEDs
> >And yet, you notice it didn't take an hour for some idiot to suggest going
> >on Ebay and getting exactly this junk. People wonder where my short
> >temper comes from.
> >
> Those are the guys who subscribe to Nigel Tufnel logic. ("But this one
> goes up to 11.")
Oh, y'know, if it isn't one garberation it's another. "Oh, but these ones
are DOT approved!" "Hey, shuddup, mofo, I was just telling him they're
available, not saying they're more gooder than regular bulbs!" Same old
same old...
> >Right. But remember, that still doesn't solve the optics problem. You
> >would either need a LARGE number of LEDs, VERY closely packed together, or
> >the aforementioned fancy optics.
> >
> That is (maybe was, depending on the cost of the Trucklite option...)
Figure, I donno, at the retail level, maybe $40 a pop
> exactly my plan. Standard perfboard would allow you to create adensely
> packed array of LEDs. A solid plane of light-emitters. Any less dense
> and you *immediately* violate the optics assumption that I described.
That plane would have to be *VERY* contiguous and VERY dense, and I'd
still want to see some dispersion optics, even if just some off-the-shelf
protokludge material, between the LEDs and the lens.
> <pulling pin on hand-grenade>
> So wouldn't it make sense....
> <tossing into room....>
> to use a small number (and it could even be as large as a dozen) of
> standard lamp formats....
> <running away quietly>
> for automotive headlamps too, so that we avoid the nightmarish plastic
> abortions (but they look so KEWL!) found on so many cars now?
> <waiting for the earth-shattering "Kaboom">
Where's the kaboom? I would strongly favor this idea. A dozen is too
many. The job could be done with adequate deference to styling variation
with six.
DS
Randy
I work for UPS. All of our new trucks have the LED S/T/T lights.
These things are FAR brighter than the standard incandescent bulb set
up. I haven't had a unit apart to see what makes them "Tick". It may
be highly polished reflectors or ? When I go to work later today,
I'll ask the Head Wrenchturner, maybe he can shed some light on this
subject :>)~
--
The probability of someone watching you is directly proportional to the stupidity of your actions.
Daniel Stern Lighting
> I work for UPS. All of our new trucks have the LED S/T/T lights.
Yup.
> These things are FAR brighter than the standard incandescent bulb set
> up.
There are numerous models of especially the 4" round Stop/Tail/Turn unit,
with anywhere from five to eighty LEDs. The performance just keeps
getting better and better with fewer and fewer more and more efficient
LEDs and more advanced optics. The brightest one around, though, is
probably Peterson's 40-LED model. FedEx (sorry) uses a lot of them on
their trucks.
DS
Steve
>
>I work for UPS. All of our new trucks have the LED S/T/T lights.
>These things are FAR brighter than the standard incandescent bulb set
>up. I haven't had a unit apart to see what makes them "Tick". It may
>be highly polished reflectors or ? When I go to work later today,
>I'll ask the Head Wrenchturner, maybe he can shed some light on this
>subject :>)~
>
Whatever the actual mechanism, it resulted from the fact that the
taillamps are a thorougly engineered package, probably from a
manufacturer such as Trucklite, which Dan already mentioned.
I would still like to experiment with making my own, but I *am* an
electrical engineer and can do some of the required testing myself. And,
I'm willing to say "well, THAT sucked" and throw them away if they don't
work.
DS
yield adverse results.
"Daniel Stern Lighting" <das...@vrx.headlamp.net> wrote in message
news:Pine.SOL.4.33.011126...@alumni.engin.umich.edu...
Daniel Stern Lighting
On Tue, 11 Dec 2001, DS wrote:
> You forgot to mention that shining red LEDs through a red lens will likely
> yield adverse results.
I didn't forget; I didn't say any such thing because it's not the case.
DS (as in Daniel Stern)
DS
switches. Backlighting coloured LEDs through different coloured silkscreened
graphics always causes weird results. Sometimes shining a red LED through a
RED graphic symbol will yield a near no-light result.
This is definitely something to consider.
DS
"Daniel Stern Lighting" <das...@vrx.headlamp.net> wrote in message
news:Pine.SOL.4.33.011211...@alumni.engin.umich.edu...
Daniel Stern Lighting
>>> You forgot to mention that shining red LEDs through a red lens will
>>> likely yield adverse results.
>> I didn't forget; I didn't say any such thing because it's not the case.
> But it is the case.
Uff da. Okay, fine, I'll play: "Is not".
> I design electronic instrument panels and membrane switches.
> Backlighting coloured LEDs through different coloured silkscreened
> graphics always causes weird results.
Indubitably. But transparent lenses of whatever color are not at all the
same as silkscreened graphics. Transparent lenses are...well,
transparent!
> This is definitely something to consider.
Then I suppose you had best inform the people that make LED automotive
lighting products that they're doing it wrong. Almost every single one of
the many such products on the market has a lens the same color as the
light the device emits. Only a very few products, such as certain-model
Volvo 3rd brake lamps, have no colored lens in front of the LEDs.
DS
Steve
>
>>>I didn't forget; I didn't say any such thing because it's not the case.
>>>
>
>>But it is the case.
>>
Oh, horsepuckey!!
Look, a colored plastic lens is a SUBTRACTIVE optical filter. It takes
an incoming stream of light, subtracts the color components that don't
match its own color, and passes the remainder.
If you use an LED source whose color (red) is within the "passband" (red
wavelengths) of the red plastic lens, there will be no adverse effect.
Period, end of story. Now, if the color band of the light source and
the passband of the filter (lens) don't overlap or else overlap only
partially, you'll get no output or diminished output. But thats not the
case here- you said "red LED behind a red lens." Works perfectly-
virtually every production LED taillamp assembly is made this way.
Douglas G. Cummins
> > Almost every single one of
> > the many such products on the market has a lens the same color as the
> > light the device emits. Only a very few products, such as certain-model
> > Volvo 3rd brake lamps, have no colored lens in front of the LEDs.
>
> Correct me if I'm wrong, but I believe that the reason for using colored
> lenses in front of colored lamps (LEDs and tinted bulbs) has to do with
> the color of a reflected light. Taillight lenses incorporate a
> reflective
> function as well as a tail/brake light and that refector must be red.
> It also prevents other incident light (sunlight, etc.) from being
> reflected in any other color than red.
You're only partially correct. The retro-reflector on a car is a
separate element and does not have to be in the same lens or even in
the same unit, so it is technically possible to have a car with clear
lens red LEDs under a clear lensed lamp while still having a red
reflector. However, as you state, there is a question of other
incident light being reflected within the lamp causing wrong-color
light to be reflected from the unit. That question is currently being
considered with retrofitters and OEMs like Lexus who have clear outer
lens rear lamps over a small red lens surrounded by chrome, as well as
numerous manufacturers who have clear lensed / yellow bulb front
turn-signal/parking lamps. It seems to me that it's mostly a
non-issue, but I don't know if that's the final say. I somewhat
prefer the colored lenses simply because I can look at a car with its
lamps unlit and know where to expect the lights to appear when brakes
or turn signals are applied.
Douglas Cummins
Calcoast - ITL
DS
light output could be at least quite "dimmed".
Why not use white LEDs? They cost more but cost seems like no object when
retrofitting LED brake lamps. With white LEDs you'd require less lamps for
the same output.
"Daniel Stern Lighting" <das...@vrx.headlamp.net> wrote in message
news:Pine.SOL.4.33.011212...@alumni.engin.umich.edu...
Daniel Stern Lighting
> Okay. I stand corrected. But I still think there could be cases where the
> light output could be at least quite "dimmed".
You stand corrected, but you still stand by your incorrect theory? This
seems contradictory to me. If the LED's output wavelength(s) fall(s)
within the transmission spectrum of the filter (lens), there is no "quite
dimmed" effect.
> Why not use white LEDs?
Because red ones are more efficacious on their own, and vastly so when one
ponders the difference between producing red light from the start, or
producing white and then subtracting everything but red.
> With white LEDs you'd require less lamps for
> the same output.
No, with white LEDs you'd require many MORE lamps for the same output.
Are you just kinda guessing at this, or...?
DS
Steve
>Okay. I stand corrected. But I still think there could be cases where the
>light output could be at least quite "dimmed".
>
>Why not use white LEDs? They cost more but cost seems like no object when
>retrofitting LED brake lamps. With white LEDs you'd require less lamps for
>the same output.
>
?!????
You've got it completely backwards, there.
With red LEDs, you don't lose any input power to light that will just
get filtered out by the red lens. With white LEDs, the bulk of the
spectrum they put out will just wind up being BLOCKED by the red lens.
Red LEDs put all their output energy in the band you need so none gets
wasted. They put out far more in-band (RED) light than a white LED.
Even a very bright white LED will have a very low brightness in the red
band by the time you filter out all the non-red components.
Besides, red LEDs are still available with much higher brightness than
white ones, although the white ones are getting better. Red,
conveniently, is still one of the cheapest and easiest LED colors to
make and the most widely used.
DS
Obviously I'm not an expert at optics. I'm a mechanical/electrical designer
with an interest in lighting. We typically use different colour LEDs for
warning and informational icons shining through silkscreened overlays and
LED or incandescent lightpipes/fiber optics for backlighting membrane
switches, LCDs and graphics. Now that it has been explained to me, filters
and colours make a bit more sense to me.
Are there any optics programs that can demonstrate filtering? I'm interested
in learning more.
DS
"Steve" <n...@spam.thanks> wrote in message news:3C190E6...@spam.thanks...
Martel
Red,
> conveniently, is still one of the cheapest and easiest LED colors to
> make and the most widely used.
I don't know about easy to make (even HP companies have had their yield
issues from time to time) but it has been around for 20+ years. Hence it is
cheap. The longer the market life the cheaper it is. The original material
was gallium arsenide. That was replaced by Aluminum Indium Gallium
Phosphide recently to make brighter parts. Additionally everyone and their
brother makes red LEDs...so competition is very tight.
The white LEDs (Gallium Nitride blue with some phosphor infused resin) are
not easy to make either. But with a market life of 6 years they are
naturally expensive. Give them 20 years and I think AlInGaP and GaN will be
relatively the same price. Right now you have 2-3 major manufacturers of
white and a lot of start up companies.
israel r t
>I think you should use green LEDs with a filter to emit red light :P
>
>Obviously I'm not an expert at optics.
Obviously...
> I'm a mechanical/electrical designer
>with an interest in lighting.
God help your clients..
DS
and upcoming agricultural and construction vehicles.
No need for rude comments. I did say I was not an expert in optics.
"israel r t" <isra...@antispam.optushome.com.au> wrote in message
news:f7kj2uolt4ilb9t48...@4ax.com...