This I did not expect! Red LED vs. Rubylith filter

LED Flashlights – General Info
1

Finally, after years of pursuing the perfect bike tail light, I have a red XP-E emitter zoomie.

WOW!

I have a UF-T20 that came with an XM-L T6 pushing 2.4 amps. Even with a red filter, it is too bright for a tail light.
Today I upgraded the SF-360 with an XP-E on an aluminum MCPCB pushing only 1 amp.

again… WOW!

Even at 1 amp, the XP-E is stingingly bright with an unbearable hotspot much worse than the XM-L at 2.4 amps with the Rubylith filter.

Does that mean I can make a really nice bike tail light driving and XP-E2 at only 700ma?

XM-L on the left : XP-E red on the right


2

Now you can try, but I think 700 ma for a tail light is way too much, but it depends on the situation, of course.

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I think 700ma will give me more headroom for a good diffuser.

4

Wouldn’t it be better to just use a diffuser or even one of those wand style diffusers with either the red filter or red led?

A rear light is purely there “to be seen”, rather than “to enable you to see with it”. It’s a marker light and really needs no beam projection or throw at all.

Even using a zoomy host on flood and aiming the light downwards 45 degree maybe more, would work better than pointing the light at approaching traffic.

5

I´m making a small tail light, using one of this lights

using the lens of a k68 ground down to fit, and I’m waiting for a red led. The lens will sit as close as possible to the led, touching the dome, it’s all flood, almost 180 degrees of visibility

I need to figure out a driver once it arrives, the driver will be in the housing for the batteries, as I intend to use the external power pack I already use for the front light (the typical 8,4v magic shine clone)

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C.D. you are right of course in many respects. It is conspicuousness that every cyclist is after. That means it needs to be noticed immediately. Wide angle and daylight conspicuous are the parameters we aim for. The only feature of most flashlight we don’t need is a focused beam. But by the same token, we also don’t want that extreme hotspot of the emitter.

So yes, a diffuser is the answer for hotspot, and yes, the aspheric lens is the answer to dispersion.

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totilde, I like that light and the aim of your build.

I am very sold on the 16-mode drivers that are limited to 4.2V.
Yes, the emitter wants to be very close to the lens.

The problem I’ve been having is that the heat from the emitter faded the red from the Rubylith filter’s center. So after a few thousand miles, it needs to be replaced.

The Rubylith was filtering so much of the white LED, that even the hotspot (the die) was no longer an issue. With the red XP-E, I need a frosted lens (which I have for the smaller lights).

The overall reason for the post was to say that the brightness of the red emitter was a lot more annoying than the Rubylith over a white LED of equivalent wattage. And the brightness too was significantly brighter than a filtered white light… probably by a decade.

Frosting will diffuse the hot spot and provide a bigger apparent spot. That may become the happy balance.

I also found 1” hemispheres at TAP Plastics. These are easy to frost (sandpaper) and they have excellent internal reflections. I still haven’t given up on making this work in a custom housing. Since the emitter at 700ma is only around 1.7W due to the lower Vf, even the heat won’t be an issue.

I do see runtime becoming a bygone issue. This revelation could bring my police mode runtime to an easy 30 hours for overnight trips. And voltage sag issues are now far back in the rearview.

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sometimes? things are like they are, simply because no one thought about a better way and tried it… and sometimes? things are like they are for a reason.

for a tail light on a bicycle? i would go with red LEDs… and i mean “regular LEDs” not our kind of high power emitters, lol. Those little red dots have high visibility.to be really noticed after dark? i would simply get them to BLINK. Blinding or mesmerizing the CAR traveling up and BEHIND YOU would be the last thing you would want.

for daylight? they make little “strobes” and they are for DAYLIGHT use, do not use them after dark they blind people and disorient them. When cop cars started to get all the circus lights on them? cops were using the “strobes” after dark when pulling people over on the highway… and sober drivers were running over the cop at the car window because it blinds and disorients people.

it took a LONG time to get all the cops to understand the strobes were ONLY for day time use, never after dark.

i’m a delivery driver, and do most of my work after dark… trust me? i have to deal with not only younger kids on bicycles? but the older “tour de france” crowd as well (i have no idea which camp you are in)

honest to GOD, the first thing i usually see up ahead on a dark road i notice? and slow down for wondering what it is? is two red lights going up-down-up-down…

…and every time its the red reflectors on the backs of the pedals makiing it, lol, VERY noticeable.

=

now, there ARE a few “modern” bicyclists around? and by “modern” i mean they have all the fancy lights gadgets all over them and the bike?? i notice the REFLECTORS first, usually… and there are one or two of them that have “reallyh cool bike headlights”?

i dont think its very SAFE, i think its blinding me and the cars behind me too…

=

i’m just trying to get across, its supposed to be about SAFETY, not about who has the brightest and most numerous lights all over them and their equipment.

be careful…

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I hope I can explain this well enough to be understood, from my limited knowledge of LEDs, and I ask anyone who has more knowledge to add more detail.

The white LEDs we use are blue LEDs + a yellow phosphor to change the emitted colour to white.

So filtering that to get red starts with a handicap as there is only a limited amount of red to get.

A red LED emits red naturally and so is much more efficient than filtering blue + yellow.

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Sedstar; yes, nighttime visibility is real simple to solve. 5% (low) on a 1 watt filter white LED is more than sufficient unless you are also competing with headlights and street lights… where you might have to kick it up to 30% (medium). The challenge is daytime, specially on a sunny day when bikes tend to “duck into the shadows”. I need a light to say “I’M HERE YOU IDIOT!” pretty much like a Mack truck horn.

At night, my bike lights up just from reflective stickers. All bikes should be painted with reflective paint!

Xv; interesting observation as that would explain a great deal about this observation. And the “just because we’ve always done it this way” seems to come from the fact that those cheap little blinkie bike lights use white LED’s behind red lenses/reflectors. Something Planet Bike got past with their SuperFlash by using a bright red LED behind a clear TIR lens.

I don’t know if you’ve noticed, but even major car companies are turning up the brightness of their tail lights. I’ve sat behind newer cars and the brake lights were annoyingly bright even in bright sunlight. I don’t know if they are doing this because the can or they too haven’t got the sweet-spot dialed in yet.

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Pictures of your setup and bike? :slight_smile:

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With redundancy, of course.

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Beleive it or not many randonneur folks

Randonneuring

actually were happy with their old steady dim red tail lights. a lot have even found way to make their new one less bright.

They spend lots of time riding at night and the argument goes like this:

If a bike rider is behind them a bright/blinking red tail light blows out their night vision.

For cars that are behind them they want to avoid the issue of target fixation and involuntary attention stimuli

Target fixation

Target fixation is an attentional phenomenon observed in humans in which an individual becomes so focused on an observed object that their awareness of hazards or obstacles diminishes. The phenomenon is most commonly associated with scenarios in which the observer is in control of a high-speed vehicle or other mode of transportation. In such cases, the observer may fixate so intently on the target that they will not take necessary action to avoid it, thus colliding with it.

The phenomenon is common amongst racing drivers, fighter pilots, motorcyclists, mountain bikers, and surfers, amongst others. When individuals target fixate, they are prone to steer in the direction of their gaze, which is often the ultimate cause of a collision.

There is an argument that there is such a thing as a tail light that is too bright.

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Yep. Especially drunks at night will aim at the taillights ahead of them, thinking they’re following another car moving at highway speed.

Too bad if you’ve pulled off onto the shoulder with a flat, or are riding a bicycle.

15

I definitely agree with the target fixation risk. If you want to be seen better, use one tilted left and one tilted right. Don’t make it bright.

16

Maybe side emitting Optic

With Deep red Luxeon

Carlo side emitting optic

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Some nice links to consider, Ouchy. Thanks!

Ronin; I do hear you about other riders. I can change my setup for a lot of different scenarios to accommodate the environment.

Infinitely variable with a thumb control or even a simple magnetic ring to dial in the brightness would be very useful.
As for flashing lights, drivers complain at about dusk if you still have flashers on. I’m going to call the main forward light flashing optional (again, remote switch is very useful here!) as they will work wonders in tense or tight situations; but once in the open, fixed light after dusk is highly recommended. And in general, it is not night time that is a cyclist challenge… it is the commuter that has the greatest challenges. People that commute year round usually face all the elements including dark, dawn, dusk overcast or bright sunlight. On my daily route, I give these cycling guys and gals full latitude on lighting. The only thing drivers fixate on at these hours is their freakin’ cell phones.

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…BTW: As an update - the opinion of fellow riders is that my lights are comfortable to ride with during the day.
The simple red led at 1amp using the 17-mode driver gives anyone a usable bike tail light for an upgrade that’s less than $10.
Several nice aspheric lens hosts out there now, including the 26650 options for improved runtime.

I’m still open for some bike specific driver implementations. I’ve started ordering the 17-mode drivers in bulk. I’d rather get my stash from Mtn Electronics.

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If you do start selling them complete as a staple tell us! :smiley:

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A group buy might reveal if the need is big enough.