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Old 03-24-09, 03:32 PM   #101
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Well, it has a driver so the light output is very nearly constant.
Having a driver does not always mean constant current. Many are input voltage dependant.
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Old 03-24-09, 03:39 PM   #102
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Having a driver does not always mean constant current. Many are input voltage dependant.
Yes.

I'll do some more run tests and take more measurements.

One of my mates has an emeter, I'll hook it up to that.

I only took one voltage measurement at the LED because it was a bit fiddly and blinding at the same time
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Old 03-24-09, 07:18 PM   #103
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Planet Bike's "blinky "Super Flash.." They are amazing.
Agreed. I just picked up two "Stealth" models at REI (as far as I can tell, the only difference is the shell -- black/white versus black/red). They are significantly brighter than my old NiteRider taillight.
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Old 03-24-09, 07:26 PM   #104
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once my K2 red arrives, I can give you a description of the difference in brightness between the K2 red and PB super flash.
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Old 03-24-09, 08:03 PM   #105
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once my K2 red arrives, I can give you a description of the difference in brightness between the K2 red and PB super flash.
Much, much, much brighter.

I stood in the road with both turned on in broad daylight a fair way from the house and my partner couldn't tell the superflash was turned on, while the "Ultrafire WF-501B Philips Luxeon K2 Red LED Flashlight" was bright and clearly visible.

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Old 03-24-09, 09:46 PM   #106
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I'm pretty sure you can snap these K2 red lights right into frame pump mounts that mount directly to the frame.

topeak road morph mount should work pretty good, if you have a spare one lying around.
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Old 03-24-09, 11:56 PM   #107
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Well, it has a driver so the light output is very nearly constant.

As the battery voltage drops the current draw increases so that the watts supplied to the LED remains the same.

With a fresh battery the voltage is high and the current draw is low.

With a tired battery the voltage is lower and more amps are taken from it to compensate.

This enables the driver to keep the current (and therefore the voltage) at the LED the same.

Having said that, before the LED went out I shone it on a white surface, then when it went out I did the same immediately after fitting a fresh battery and it was a little brighter.

Maybe the when the battery is nearly depleted it can't supply enough amps to keep the wattage the same and then the output drops ? I don't know for sure, more run tests and measurements required.

I'd say that if the light output did drop as low as 50% before going out, it must have been in the last 2 or 3 minutes.



Hope this helps....
There are plenty of DX lights with drivers which are not regulated. Take a look at all the P7/MC-E lights for example.
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Old 03-25-09, 04:20 AM   #108
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Sorry if I missed it if you mentioned it, but is there any side visibility, or is it a laser beam pointed straight back?
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Old 03-25-09, 08:12 AM   #109
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There is side visibility. I will post daytime pics and nighttime pics today, unless Unknown beats me to it, I promise. He has way more testing gear/experience with lights obviously, I am more of a newbie to flashlights but do own some mt-e p7's for my commute. DX and candlepower forums is addicting.

In daylight I set it up on the hood of my truck and walked down the block and it was highly visible of offset angles of 25 degrees or more (checked by walking back on the sidewalk on the opposite side of the street) at between 25' and 250'.
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Old 03-25-09, 11:09 AM   #110
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In daylight I set it up on the hood of my truck and walked down the block and it was highly visible of offset angles of 25 degrees or more (checked by walking back on the sidewalk on the opposite side of the street) at between 25' and 250'.
I'd pretty much agree with that, I had intended to do the same thing and take some measurement, then calculate the angle.

I would say that any car approaching from behind would definitely be in the cone of red light until it was very close indeed - at which point as well as having noticed you, they will probably be greatly relieved to be out of the line of fire.

I will be experimenting with a different lens if it ever arrives from DX - I suspect it is lost.

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Old 03-25-09, 10:15 PM   #111
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I just want to thank you guys for pioneering this. It may turn out to rival the popularity of P7s, but pointing backwards this time.
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Old 03-26-09, 03:27 AM   #112
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Having a driver does not always mean constant current. Many are input voltage dependant.
Hi Znomit,

Before I do any more tests what would you recommend ?

I'd rather not remove the LED so measuring current at that point isn't possible.

Any ideas of what might yield valuable information ?

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Old 03-26-09, 04:12 AM   #113
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Hi Znomit,

Before I do any more tests what would you recommend ?

I'd rather not remove the LED so measuring current at that point isn't possible.

Any ideas of what might yield valuable information ?

Get two and compare one with flat batteries and one with fresh? Its really hard to make meaningful comparisons when you have to stop and swap batteries.

Or measure the battery voltage over its useful runtime and run off an external power supply, comparing the different voltages.

Of course, I expect this thing is plenty bright enough even when nearly drained, so who cares?

Check out here for some Input Voltage/LED current charts. Not so constant.
http://www.leddynamics.com/LuxDrive/...Micro_App.html
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Old 03-26-09, 05:33 AM   #114
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and the LED/driver for these ultrafire K2 lights, at least what's written, says it can take 3.0V~18.0V
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Old 03-26-09, 05:45 AM   #115
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ok, my little point and shoot was not able to take any decent day or night shots, so you'll just have to trust me or cajole unknown into taking some pictures.

I did the wet finger test and the flashlight is direct drive, however, I do not know enough or have enough equipment to determine if it is regulated.

the things bright. trust us.
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Old 03-26-09, 05:46 AM   #116
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just buy one.
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Old 03-26-09, 08:26 AM   #117
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Ok, pdxsteve has me about to order one.

Unknown Cyclist, whatever happened with that lens you ordered back on the first page? Now that you've tested it, is it needed?
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Old 03-26-09, 08:33 AM   #118
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Ok I ordered one.
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Old 03-26-09, 08:54 AM   #119
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I'm pretty happy with my light output. I have other lights for side/close visibility and trust me folks, cars will be happy that this flashlight does not spill to the sides really close up. It hurts the eyes.


I curious to see what the lense does if you ever get it, unknown.
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Old 03-26-09, 10:06 AM   #120
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Get two and compare one with flat batteries and one with fresh? Its really hard to make meaningful comparisons when you have to stop and swap batteries.

Or measure the battery voltage over its useful runtime and run off an external power supply, comparing the different voltages.

Of course, I expect this thing is plenty bright enough even when nearly drained, so who cares?
It's still very bright, until just before it goes out.

I'm used to seeing white spots for ages, so the red ones make a nice change.

BTW, you should always look directly at a high power LED to check it is working and see how bright it is..

Anyway, how about this - I've got some solar panels that output a few volts when I shine a torch on them.

Assuming they collect red light, I could set up the torch a few inches from one and measure the voltage produced by the solar panel every 10 mins for 4 hours.

Obviously the initial highest reading would be 100% and the lowest reading (if any) would be 0% when the light is off.

I'm not sure the output is linear so 50% might not be 50% but it would indicate how long the output is constant and how quickly it drops - a graph might be interesting ?

Any thoughts on this test procedure ?

I did this with my P7 on low to check if the output is regulated and there was no drop at all - but it does have a higher input voltage (2 x 18650).

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Old 03-26-09, 10:09 AM   #121
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I did the wet finger test and the flashlight is direct drive, however, I do not know enough or have enough equipment to determine if it is regulated.
I'm not sure what you are refering to here ?

Are you courting ?

What's the wet finger test ?

You are saying it's direct drive but might be regulated ??
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Old 03-26-09, 10:14 AM   #122
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Unknown Cyclist, whatever happened with that lens you ordered back on the first page? Now that you've tested it, is it needed?
Damn thing hasn't arrived yet, despite being dispatched several days before the torch.

I'll email DX right now.

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Old 03-26-09, 11:38 AM   #123
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This thread has gone on for 5 pages but alas no beamshots. I'm sure the output is fantastic and will cure cancer and lead to the lost souls' redemption but sometimes a picture's worth a thousand words.

My two units should be arriving in the mail soon and I promise beamshots galore.
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Old 03-26-09, 12:34 PM   #124
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I'll give it a go, any advice on camera settings for a beamshot ?
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Old 03-26-09, 01:18 PM   #125
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Unkwown, I don't have experience with settings yet, but here's a link that may be helpful:

http://www.candlepowerforums.com/vb/...ad.php?t=95336

I read somewhere that it's recommended to set the camera setting to DAYLIGHT white balance (if your camera has such a mode).

If you google "camera settings for beamshots" you'll find some links.

Looking forward to your photos!
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