New Rear Array . . . Finally!

Ishrub said:

How do you get the brake and tail to illuminate at different intensities though?

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The LED drivers incorporated feeds less or more current. But I find that often, driving LEDs with a lower current does not diminish their visibility so much as how hot they get. And then as you keep dropping, suddenly they simply glimmer. mfrs cant afford to adjust each one - so they give themselves a decent low end margin to avoid glimmer.

There are solutions where there is an array and more LED emitters are used on BRAKE than just TAIL. But I have yet to see a replacement bulb that has this. Let alone a red one. This imo is the real way to go.

Also I believe that lights designed to WARN (brake and indicators) need to be physically segregated from position markers. This is NOT easy to do on a bike. I have positional markers in my top case and brake lights in the indicator housing. But it's not ideal and I may get a set of Kellerman Attos for additional brake. So in something like Steve's case I would use maybe the HYPERLITES only in braking mode. And I'd FLASH them.

1olbull said:

Perhaps there is a wave length or configuration difference between incandescent and LED???

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IT IS EXACTLY THAT. Incandescent bulbs give of a redder spectrum than LEDS which tend towards the Blue end.

Most replacement bulbs make a big point of being 6000K - Look red to you?

And as said earlier in the other thread. Steve even acknowledges that his LED bulbs were no better than OEM type too.
LED taillight project. Can the taillight be opened?

DEcosse said:

A WHITE LED is NOT the same as a broad-spectrum incandescent 'white' light - behind a Red Filter Lens, you should really use a RED LED, otherwise it will be cutting off significant amount of light.
The Red Filter (because that's what it is - it only lets red light wavelength through) is going to transmit majority of the generated light from a narrow spectrum red LED compared to the loss from an incandescent but even more loss from a white LED (albeit the LED probably generates much more lumens to begin with)
The general 'rule' is always use same colour LED as the LENs filter is going behind.
i.e. Yellow LEDs for Turns and RED LEDs for tail/stop
Of course with a coloured LED you can also use a clear lens.

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1olbull said:

I bought two different sets of this type.
Both fit inside the OEM lens just fine.
Both suck as they are not visibly better than the OEM 1157.
Just got a new rear Exedra Max on way home from Leakey Texas.
When that wears out, I shall get serious in determining the actual light values for the various bulbs.

FYI - these are what I have:

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And more from that same thread - worth a read of it all.
LED taillight project. Can the taillight be opened?

1olbull said:

Chris,
I have been researching these Luxeon LED applications and may have come up with the reason for my issue regarding the non improvement of the 1157 LEDs I have tried in my OEM tail light.
An OEM lens for incandescent lights filters different wave lengths than does a lens designed for LED; therefor, an LED under a OEM lens is NOT effective.
What sayest youse re: this?

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1olbull said:

Thanks for chiming in, Ken.
What I learned was that a standard red lens for a 1157 type bulb filters different wave lengths and are not so compatible with those of LEDs.

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DEcosse said:

Have to disagree with you on the bolded statement - they pass RED Light - which is a VERY important qualifier
It's quite fundamental - the viewed light looks RED because that is the wavelength it is passing, whereas the (incandescent) source is made up of a broad spectra of wavelengths.
OK - if it looks pink, then admittedly it's not a perfect 'notch' filter* - but it's important to recognize that PREDOMINANTLY it is the RED component of the spectrum that is being passed.
All well & good (sic!) for an incandescent - that is a broad spectrum light source of multiple wavelengths - the red filter allows the red wavelength to pass and blocks the others.
So yes, already it is quite inefficient for the emitted red light vs the total emitted light from the bulb
Now move to an LED - a White LED is NOT composed of the same spectral components as an incandescent; the red component is going to be SIGNIFICANTLY less.
The fact that is passes at all is because the red filter is not a perfect 'notch' filter.
The bottom line is that a RED Filter passes RED Wavelength light - the highest percentage of total total light that is passed through a RED filter is going to be from a RED LED - even if the total emitted raw lumens is less - because ALL of the light is going to be a much narrower wavelength bandwidth, much closer to matching the red filter.

* The wavelength of a RED LED is VERY narrow - certainly MUCH better than the bandwidth of the filter
So the filter is going to pass virtually all of the light (OK there may be some attenuation but that is going to be small relative to the non-RED blocking)

Some reading material - https://www.maximintegrated.com/en/app-notes/index.mvp/id/3070



i.e. there is NO Red Wavelength component in a White LED - the only reason it emits through the LENS at all, is because the LENS itself is not very focused on a narrow RED wavelength.

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Ishrub said:

..... How do you get the brake and tail to illuminate at different intensities though? ...

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barbagris said:

The LED drivers incorporated feeds less or more current.....

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For an LED, the intensity is not linearly proportional to current, as an incandescent would be
The proper way to change the intensity is NOT to vary the current, but use a PWM (Pulse Width Modulator) - they should apply optimum current at all times, but the duty cycle of on vs off (at a frequency not discernible by human eye as 'flashing') is what makes it appear brighter, or dimmer.

I built a driver module for an integrated Running/Stop/Turn lamp array -


For simplicity for the demo, I'm just using a single 5mm LED - but this circuit will drive a full high power LED array
When you observe the LED at the lower intensity, it is in fact 'flashing' - you just can't see the flash of it turning on and off with your human eye and instead you 'average' what you are seeing between it being full on or full off. For Stop, it has no 'flashing', it is simply full on. The current for 'on' is the exact same in either case.
For turn, it is just being turned 'full-off' per the turn signal flash frequency (which is much lower than the PWM frequency)

Per the opening note of my post, the operating current is optimum and constant for the LED and the pulse width of on to off time is what is being varied (or turned on/off in case of the turn)

(so you wouldn't use a "dual-element" LED lamp for this, it would just be a single element with spec matching your brake light requirement - and the running light would be pulse width modulated for the lower intensity but still utilizing the high power Brake LED)

1olbull said:

Chris:
The more I research this the more me reckons the incandescent 1157 is better than any LED replacement.
See Web Bike World testing.
webbikeworld led 1157 - Google Search

I am rather interested in the Sylvania Zevo Red:
and the Phillips P21 5W Red:

Sure wish I would have done some metering to compare this before I buttoned it all up and installed the rear wheel.
Fortunately I have many more lights now than just the OEM POS, so not too concerned.

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Good link to the web bike world article but sadly it appears even more out of date now having last been updated in 2012 and LEDs have become mainstream with many tech improvements etc since then.

DEcosse said:

The proper way to change the intensity is NOT to vary the current, but use a PWM (Pulse Width Modulator)

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So true. But getting all that inside a bayonet cap is tricky and awkward to heat sink. I can't stand the infernal in-line boxes that are occasionally and correctly used. There's never enough space to hide the buggers on a bike. That and you're ruddy miles away.

1olbull said:

The OEM light is a white incandescent 1157 inside a red lens.
Seems a white LED should also work, but I do not know the science . . . yet.
I have read that a red lens works better with a red LED. Why the difference, I do not know and peeps reporting this do not explain how they know . . .
Perhaps there is a wave length or configuration difference between incandescent and LED???

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I believe that if you install a white led inte stopping lens, the fact that they are stronger will give you a less than red beam going through the middle. If its red well you have a stronger beam in the middle but at least its all red.

1olbull said:

The OEM light is a white incandescent 1157 inside a red lens.
Seems a white LED should also work, but I do not know the science . . . yet.
I have read that a red lens works better with a red LED. Why the difference, I do not know and peeps reporting this do not explain how they know . . .
Perhaps there is a wave length or configuration difference between incandescent and LED???

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See here - Calculating the Emission Spectra from Common Light Sources

Here is the wavelength spectrum of an incandescent bulb:




Note that it is predominantly RED

Here is wavelength spectrum of a WHITE LED:
How is white light made with LEDs? | LED Lighting Systems | Lighting Answers | NLPIP



The two graphs are showing two different technologies of producing white - but note that in either case the RED light component (>650nm) is extremely low.

A RED lens is in fact a RED FILTER - i.e. it only (or predominantly) only lets the RED wavelength light through - it doesn't 'colour' the total light emission, only filters through the red component, which is why the emitted light is RED and NOT White!
i.e. the Filter allows through the 700+ nm wavelength and blocks the lower wavelength components.
You can see from the graphs that the major components of the white LED are well below the RED zone - the fact remains that the filter (the red lens) is not a perfect red filter (with a narrow notch band) but will tail off and allow some of that lower band through - but nothing near the peak of what it is emitting from the source.

SO - a White LED that has more RAW Lumens than another lower output White LED will indeed emit more Light through the lens relatively - however NOT vs an incandescent or indeed a RED LED

Spectrum of a RED LED is very narrow and will match up to the RED Filter

Here is a table of wavelengths of some modern LEDs

LUXEON Rebel Color Line

You will see the RED have a very narrow bandwidth of 620- 645 nm



(All of the colours of individual LED types are superimposed onto one chart - in this case the std 'RED' is the middle of that group of three between the Amber and the Far Red, and centered on ~ 630nm)
Again, to be clear, each individual colour type of these product LEDs is only going to have ONE curve - they all just been superimposed on a common graph to show their relative spectrums

In the same product line, see here - https://www.lumileds.com/uploads/28/DS64-pdf

for the WHITE LED