3 Watt LED Bike Light
Experiments
June,
2008, Rev f
Michael Krabach
Contents
Light and Beam Measurements
It is always difficult to measure the total amount of light from a bike light and almost impossible without expensive lab equipment. Beam assessment is also very subjective depending on the type of riding. To compare the prototypes I have used two crude methods. The first is with a box lined with aluminum foil and with a translucent panel inside to get the light diffused a little bit more. A hole was cut in the front of the box to shine the light through, and another hole to hold the light meter. I used a DX SKU-5100 digital Lux meter. The second method was to use a photo voltaic solar panel measuring the light output with a voltmeter. I placed a shiny #10 tin can over the panel to deflect side light down to the panel, hoping that all the light would be integrated by the solar panel. The top of the tin can also gave me a reference height for all the lights. All values are only relative to each other and are not absolute.
The below data
shows that the light box seem to give the most consistent values.
That is, three Cree LEDs should give three times a single Cree LED.
The solar panel data does not show that. (I will have to look into
that phenomenon.) The Mag-lite prototypes 7, 8, with the tri-optics,
do not utilize the light as good as the L2 optics for the rest of the
lights. Prototype 9 suffers from not being as good LEDs on the
prefabricated module. The Q5 vs P4 bin LEDs show an increase of 28%
and 21%. Earlier readings showed only 18%. The 8 deg diffuser covers
for the L2 optics reduce the light (for all the readings) 12%, 2.5%,
6.5%, and 8.7%. Prototype 4 showed an increase in brightness using
the diffuser, obviously trying to confuse me. What ever the value, (I
have seen published values of 15%), the beam is greatly improved with
the diffusers. The data also shows that my original “Cheap
20 Watt Bike Light” only puts out about ½ the light
as the newer triple LED models.
I have added some flashlights
that I have for a comparison with the bike lights. The dimmest is the
Cateye bike light, and that is after I modified the original by
replacing the original LEDs with 14,000 mcd LEDs. My impression of
that modification was that it doubled the brightness.
The
Task Force flashlights (Lowes) show that the new Cree version is
about twice as bright as the old Luxeon version. But looking at the
Ultrafire WF-606A which as a 3 watt Cree LED vs the Cree Task force,
which is also 3 watt, I am inclined to think that my light box
will bias a broad beam over a narrow one. (When you think how the
light reflects and re-radiates inside the box with the translucent
panel, that conclusion appears logical.)
Beam
patterns are shown for a driveway with milk-white jars to
indicate distance. The jars start about 12 feet down a driveway from
the bike and spaced about 6 feet apart there after. The orange street
glow is typical of full-cutoff high pressure sodium vapor residential
streetlights. It gives a nice reference intensity for comparison with
the bike lights. The lights were aimed at an optimal distance in
front of the bike, which varied depending on the prototype. The
camera exposures were all the same at f2.9 at 1/2 sec, ASA 400
for the front bike lights. Camera exposure for the rear flashers on
the garage were all the same at f4.5 for 1 sec ASA 100.
The
other beam photos on the ceiling show the raw beam pattern
with the tape X spanning 20 degrees. The camera exposures were on
auto so the brightness is not representative of the lights.
|
Prototype version |
Driveway |
Ceiling Beam Pattern |
Light Box Lux |
Percent of brightest |
Light Box Lux |
Solar Panel Voltage |
Percent of brightest |
|---|---|---|---|---|---|---|---|
|
Prototype 1 - Resistor limited 10 watt module using Mag-lite reflector. |
|
|
5150 |
70% |
|
5.0 |
89% |
|
Prototype 2 - Triple Cree,
Buckpuck regulator with variable brightness, surplus power
supply heat sink |
|
|
7150 |
98% |
8200 |
5.6 |
100% |
|
Prototype 3 - Double Cree with individual current regulators and switches. |
|
|
1900 each, 6v lantern |
26% |
4100, 6v lantern |
4.5 |
80% |
|
Prototype 4 - Single Cree Q5 with heat sink, On/off clicky switch. |
|
|
3120, 6v lantern |
43% |
3200, 6v lantern |
3.5 |
62% |
|
Prototype 5 - Single Cree P4 with aluminum stock heat sink. |
|
|
2430, 6v lantern |
33% |
2600, 6v lantern |
3.0 |
55% |
|
Prototype 6 - Triple Cree,
variable brightness, aluminum stock heat sink. |
Same beam pattern as Prototype 2. |
|
7300 |
100% |
8000 |
5.4 |
96% |
|
20 watt Halogen |
|
|
4040 |
55% |
|
3.5 |
62% |
|
Prototype 7 - Triple SSC,
Mag-lite “C” head, bFlex controller. |
|
|
6100 |
83% |
|
5.5 |
98% |
|
Prototype 8 - Triple Cree,
Mag-lite “D” head, Buckpuck regulator with variable
brightness |
|
|
5800 |
79% |
|
5.5 |
98% |
|
Prototype 9 – Module
with three 3 watt LED emitters on plate, Mag-lite “C”.
Buckpuck regulator with variable brightness. |
|
|
4020 |
55% |
|
4.4 |
78% |
|
Cree Ultrafire WF-606a Flashlight 3v C2 battery |
|
|
950 |
13% |
910 bare bulb |
|
|
|
Mag-lite 2 ”D” cell
with 3 watt Luxeon upgrade bulb |
n/a |
|
450 |
6.2% |
|
|
|
|
Task Force (Lowes) 2 “C” cell with 3 watt Luxeon LED Flashlight |
|
|
620 |
8.5% |
|
|
|
|
Task Force (Lowes) 2 “C” cell with 3 watt Cree LED Flashlight |
|
|
1350 |
18% |
|
|
|
|
MadMax Plus WO Luxeon AA Flashlight conversion |
|
|
800 NiMH |
11% |
|
|
|
|
Cateye Opticube 5 LED bike light, 4 alkaline batteries. With replacement LEDs. |
|
|
290 |
4% |
|
|
|
|
Prototype 10 – Red Flasher Cree red
LED with L2 Optics and multi-mode controller. |
|
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Prototype 11 – Yellow Flasher, Cree
3 watt white LED, multi-mode controller, no optics. |
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Prototype 12 – Red Flasher Cree red
LED, multi-mode controller, no optics. |
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VistaLite VL700
- 7 LED Red Flasher |
|
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VistaLite VL500 - 5 LED Red Flasher |
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Five Flashers - Side Visibility views of the five types. Flashers are in steady mode for photo only. |
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Flasher Size Comparison Prototype 10 at
top, |
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Prototype 13 – Red Flasher with two 1 watt LEDs, multi-mode controller. No optics. |
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Prototype 14 – Similar to Prototype 6 but using 8 degree optics. |
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Prototype 15 – Red Flasher with 2 Cree LEDs, multi-mode controller. No optics. |
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Prototype 16 – Red Flasher with two 1 watt Leds, multi-mode controller. Using off-the-shelf flasher for conversion. Clear cover. |
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Prototype 17 – An adaptation of automotive clearance light for a tail light. Steady light, no flashing. |
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