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Cheap, powerful rear light?

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Old 03-12-09 | 08:47 AM
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Cheap, powerful rear light?

I have come across this light, but I haven't bought one or seen one. Anyone know anything about them?

https://www.dealextreme.com/details.dx/sku.20333
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Old 03-12-09 | 08:52 AM
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looks promising, nice find.
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Old 03-12-09 | 09:23 AM
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Yep, nice find.

Ok, bought one.
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Old 03-12-09 | 11:02 AM
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Dang it...just when I thought I was all set with my rear lighting, this pops up. Maybe a couple of these attach to the seat stays.
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Old 03-12-09 | 11:06 AM
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Just bought one of these as well - Glass Optic
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Old 03-12-09 | 11:43 AM
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tell us how it goes.
but I'm curious, why a converging lens?
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Old 03-12-09 | 11:45 AM
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Originally Posted by sknhgy
I have come across this light, but I haven't bought one or seen one. Anyone know anything about them?

https://www.dealextreme.com/details.dx/sku.20333
One Hour Run Time.

Way Too Short.
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Old 03-12-09 | 11:55 AM
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Originally Posted by AEO
tell us how it goes.
but I'm curious, why a converging lens?
It's a torch, without a secondary lens it's only going to be visible from directly behind.
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Old 03-12-09 | 11:56 AM
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the 1hr run time is probably inaccurate because the power draw and run time don't add up according to the posts on DX.
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Old 03-12-09 | 11:58 AM
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Originally Posted by Unknown Cyclist
It's a torch, without a secondary lens it's only going to be visible from directly behind.
then wouldn't you want a diverging lens?
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Old 03-12-09 | 11:59 AM
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Originally Posted by 10 Wheels
One Hour Run Time. Way Too Short.
I'm pretty sure that's a mistake.

Red LEDs are usually lower voltage than white, also they claim 800mA regulated which would probably give more like 3 hours.

Personally I suspect the LED is receiving less than 800mA and runtime will be proportionally longer.

If it is running at 800mA expect dinotte levels of brightness !!

However, I'll let you know when it arrives...

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Old 03-12-09 | 12:12 PM
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Originally Posted by AEO
then wouldn't you want a diverging lens?
My thought too, the reviews are talking about setting things on fire and melting plastic, not casting a nice wide, visible from every angle beam.
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Old 03-12-09 | 12:16 PM
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Ok, here's some specs: Luxeon K2 red LED

Lumens 75 lm @ 700mA, 45 lm @ 350mA.
Max Continuous Current 700 mA
Forward Voltage 3.4 Vf
Dominant Wavelength 627 nm
LED Type K2
Radiation Pattern Lambertian
Weight 0.78g

Due to thermal management I suspect it's more likely to be about 500mA than 800mA.

Also all the torches I've bought from DX so far have been below the claimed power rating.

Runtime tests, volt and amp measurements to follow.....

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Old 03-12-09 | 12:40 PM
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Originally Posted by AEO
then wouldn't you want a diverging lens?
If it's converging, it has a focal point ?
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Old 03-12-09 | 02:37 PM
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depends on how you want to use it, collimator, converging and diverging lenses.
the curved mirror collimator on the light seems to give a nice beam angle from the shots on the site.

depending on the power it has, it might even be nice to use a diffusion lens on it.
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Old 03-12-09 | 05:22 PM
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Originally Posted by AEO
depends on how you want to use it, collimator, converging and diverging lenses.
the curved mirror collimator on the light seems to give a nice beam angle from the shots on the site.

depending on the power it has, it might even be nice to use a diffusion lens on it.
Looks like it has a simple O/P reflector in it, to me.
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Old 03-12-09 | 07:16 PM
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yes, nice find. just ordered two.
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Old 03-13-09 | 10:24 AM
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$10. Free shipping. That's a find.

I've been looking for something like this -- a rear light to run on 18650 batteries.
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Old 03-13-09 | 10:28 AM
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Originally Posted by AEO
then wouldn't you want a diverging lens?
Ok..find me one ?
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Old 03-13-09 | 05:15 PM
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not a clue.

Converging or flat lens is the norm since the diverging part is easily attained by just removing the collimator.
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Old 03-13-09 | 05:30 PM
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Originally Posted by AEO
not a clue.

Converging or flat lens is the norm since the diverging part is easily attained by just removing the collimator.
You are going to have to clarify what you mean by collimator - this torch has appears to have a simple O/P reflector and as the LED is recessed maybe 20mm inside the front of the torch removing the REFLECTOR will have little beneficial effect.

I do have similar size ultrafire torches here and removing the reflector while wasting a lot of light allows a wider angle cone of light to be emitted - however it isn't anywhere near wide angle as a cycle rear light.

I'm hoping it will be possible to harness all the light output and direct it where required.

I'll experiment more when the torch arrives.

It may well be that better results can be achieved if the assault crown didn't block so much light.



EDIT: Interestingly, I just realised that the red Luxeon LED is a Lambertian so most of the emitted light is going to go straight out the lens without touching the reflector anyway, so removing the reflector will have much less effect than it does on my white LED Ultrafire torches.

Last edited by Unknown Cyclist; 03-13-09 at 05:49 PM.
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Old 03-15-09 | 06:04 AM
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Sadly it's only one mode, which means no flashing or strobe.
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Old 03-15-09 | 06:08 AM
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Old 03-15-09 | 06:22 AM
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Originally Posted by Ziemas
Sadly it's only one mode, which means no flashing or strobe.
Suits me

There are plenty of blinky lights available

EDIT: mine's in 'packaging' whatever that means....
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Old 03-15-09 | 07:06 AM
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Originally Posted by Unknown Cyclist
EDIT: mine's in 'packaging' whatever that means....
Means it could still be another week before it ships.
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