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  1. #1
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    How many LED's does it take to outshine a 20W Halogen?

    Apologies if the question is a bit vague (because I know it varies a bit based on LED type, optics, etc.). But: I have a 20W halogen. In the lighting arms race, I'd like more light. Would 3x Cree be enough? The pictures I've seen are inconclusive. Has anyone seen both and can comment?

  2. #2
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    Quote Originally Posted by Praxis
    Apologies if the question is a bit vague (because I know it varies a bit based on LED type, optics, etc.). But: I have a 20W halogen. In the lighting arms race, I'd like more light. Would 3x Cree be enough? The pictures I've seen are inconclusive. Has anyone seen both and can comment?
    You didn't specify which halogen lamp type, but for instance:
    20W MR11 ==> 400 lumen
    20W MR16 ==> 850 lumen
    *About a 1.7A current draw on the halogens @ 12v.

    12W Triple Seoul P4 (u-bin) ==> 650 lumen
    12W Triple Cree XR-E (Q2-bin) ==> 600 lumen
    12W Triple Cree XR-E (P4-bin) ==> 550lumen
    *LEDs driven at 1A.

    Hope this helps.

  3. #3
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    Thank you. Bleh, I forgot the lamp type. I was meaning MR16. The specs I've seen on bulbs vary wildly, but I had thought that MR16 output was slightly lower. I mean, low-end HID output is around 600ish lumens, if I recall?

    This seems to indicate that four Seoul P4 U-bins will give approx. 868 lumens (I say this as if it's a precise measurement. :P ) Which means if I want to equal my MR16 halogen, I have to use 4 top-end LEDs, the only advantage being that I'm drawing 1A instead of 1.7A. OK, and bulb longevity, I guess. So in terms of brightness alone, it seems that halogen still holds the crown. Anything more than 4 high-output LEDs is getting kinda ridiculous if I'm trying to best the halogen light output.

  4. #4
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    I can think of one major advantage of the LED setup over a more fragile hotwire setup... redundancy or in the case of getting out of a forest alive... survivability. If you are without a backup system, it could be a long night.

    Also if you rig it to do so, the LED's can be dimmed and will sustain the same colour temperature while varying luminous output.

  5. #5
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    Quote Originally Posted by mudmojo
    I can think of one major advantage of the LED setup over a more fragile hotwire setup... redundancy or in the case of getting out of a forest alive... survivability. If you are without a backup system, it could be a long night.

    Also if you rig it to do so, the LED's can be dimmed and will sustain the same colour temperature while varying luminous output.
    Considering the $2 cost of a replacement bulb, I don't worry about filament fragility and just carry a spare

    And regardless of system, some form of backup lighting is important.

    LEDs are undeniably the way forward though. I'm going to build an aschelot-inspired Cree in the next couple of weeks (excellent instructions- thanks for putting them up!)

  6. #6
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    Quote Originally Posted by Praxis
    Thank you. Bleh, I forgot the lamp type. I was meaning MR16. The specs I've seen on bulbs vary wildly, but I had thought that MR16 output was slightly lower. I mean, low-end HID output is around 600ish lumens, if I recall?

    This seems to indicate that four Seoul P4 U-bins will give approx. 868 lumens (I say this as if it's a precise measurement. :P ) Which means if I want to equal my MR16 halogen, I have to use 4 top-end LEDs, the only advantage being that I'm drawing 1A instead of 1.7A. OK, and bulb longevity, I guess. So in terms of brightness alone, it seems that halogen still holds the crown. Anything more than 4 high-output LEDs is getting kinda ridiculous if I'm trying to best the halogen light output.
    I got my lumens info on the halogens from here.
    Running 4 leds is a little more problematic in how to power them, but it can be done. You either get into the 18v battery range (running the LEDs in series), have to risk a series-parallel wiring scheme (which can cause issues) or you can use two drivers (drive each pair separately).

    I prefer two separate, triple LED lights. One more floody beam on the handlebars, and a slightly tighter-beamed triple on my helmet. Then I've got 6 LEDs, for a total of well over 1000 lumens. The bar/helmet combo is the choice of many.
    Good luck.

  7. #7
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    Quote Originally Posted by achesalot
    I got my lumens info on the halogens from here.
    Running 4 leds is a little more problematic in how to power them, but it can be done. You either get into the 18v battery range (running the LEDs in series), have to risk a series-parallel wiring scheme (which can cause issues) or you can use two drivers (drive each pair separately).

    I prefer two separate, triple LED lights. One more floody beam on the handlebars, and a slightly tighter-beamed triple on my helmet. Then I've got 6 LEDs, for a total of well over 1000 lumens. The bar/helmet combo is the choice of many.
    Good luck.
    AchesAlot,

    Just curious but with your setups if the LED's burn out or something would the other LED's still shine or will they all be turned off? I was reading the Princeston Switchback phamplet and they said they have some technology (wiring?) so that each light is wired seperately or something so if one LED burns out the others will keep doing and not have yo uin the dark or worst while you're going ~70kph downhill.


    Zero_Enigma

  8. #8
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    Quote Originally Posted by Zero_Enigma
    AchesAlot,

    Just curious but with your setups if the LED's burn out or something would the other LED's still shine or will they all be turned off? I was reading the Princeston Switchback phamplet and they said they have some technology (wiring?) so that each light is wired seperately or something so if one LED burns out the others will keep doing and not have yo uin the dark or worst while you're going ~70kph downhill.


    Zero_Enigma
    If driven properly it inlikely a led will fail.

    most setups are wired in series so if one goes open circuit they all go off. you only need one controller this way. I think most of the lightaholics on here have both a bar lighta and helmet light which provides the reundancy. If going that fast downhill....I would us 2 lights hehe.

    You can run 2 controller with 2 strings for example. This allows you to switch down to half lights aswell as provide redundancy. This doubles run time too when on half. but running 2 controllers is less efficient for a couple of reasn though. first is you have another controller, so the losses associated with the controller are doubled. The 2nd is that LEDs run more efficiently at lower currents....so running 4 at the current required same brightness is more efficient than 2 at full current. the half as bright 4 setup will use less current (burn time more than twice the full power burn time) and provide the same light.

    I can't think of a controller that that is meaty enough to run a few high power leds at full current in parallel (A circuit/device could be built/found though...i am talking off the shelfe ready build LED drivers). the problem with running in parallel with a controller that controls current (current control is prefered for leds for good brightness control) if one did pop...the current that is not used by the blown LED will have to be shared acros the other LEDs. They aren't going to like it up em. Also due to the variation in LED voltage, each LED would run at a slightly different brightness. There will prbably be more controller loss too for the parallel setup.

    Stu
    What exactly is a rigid hard tail?

  9. #9
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    Zero_Enigma. Stu pretty much said what I would say and then some.
    Anyone ever have an LED fail? Just curious.

  10. #10
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    Wow... server must be hosed. All my posts are doubled.

  11. #11
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    I've NEVER heard of an LED failing open circuit unless seriously abused. If just slightly abused they will get a lot dimmer, but even then they don't tend to fail open circuit - that's kind of inherent to the way they work being solid state semi-conductor devices.

    Your controller is more likely to fail, but if properly built that's also extremely unlikely - I'd suggest the most likely cause of failure is faulty wiring. All in all, the reliability should be several magnitudes better than hotwires.

    BTW I'm unconvinced by some of those figures - experiment and reports I've seen would both suggest that Q2 Crees are superior to U-bin P4s (bearing in mind that the bottom of the U-bin is lower than the top of the Q2 bin, and I suspect the U-bins are nearer the bottom than the top). Also I've never been convinced by reports of how good MR16s are - the only real difference from an MR11 is the size of the reflector - the actual bulb inside is much the same. I have a 20W headtorch which takes loose bulbs of the same type as is sealed in a MR11 or MR16 capsule, but which has a huge 90mm reflector - even 10% overvolted this is no match for even my lowly triple Cree P3 light.

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