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  1. #1
    gna
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    Dynohub and Halogen bulbs

    Hello--

    I am building up a winter bike. The front wheel will have a Sturmey-Archer X-FDD (dynamo Drum) hub. It produces 6v, 3w. I am looking for a headlamp. I was going to build an LED light using the diagrams at pilom.com for help, but I was helping at the bike recycler last night, and they had a VistaLite 5W halogen headlamp that showed up in a box of odds and ends. It had no battery pack with it, so I tried it with 6v from some AA batteries, and it lit right up.

    I believe halogens will work on either AC or DC, so am I right in thinking this lamp will work fine when driven by a dynohub? Any problems to be aware of?

    At worst, I'm only out a buck, and I thought I could always rebuild it with an LED, so no worries if it doesn't work.

  2. #2
    You gonna eat that? Doohickie's Avatar
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    You may want to read my recent thread about dyno lighting. From what others have said, halogen bulbs don't last very long with a dyno, especially compared with LEDs. See in particur post 34:

    Quote Originally Posted by tatfiend View Post
    The claims I have seen for LED life are 50,000 to 100,000 operating hours. Depends on how well the LED is cooled and how hard it is driven. The small low voltage halogen bulbs have a reported life of 10 to 100 hours and that seems to be dependent on vibration level they are subjected to and luck. Larger size tires are bulb friendlier due to reduced vibration.
    If you already have the light, try it. It should be compatible with the hub. You may want to get a spare bulb and carry it with you though. If it works, that's a great, affordable option, even if you have to buy several bulbs at $3 a pop.
    I stop for people / whose right of way I honor / but not for no one.



    Originally Posted by bragi "However, it's never a good idea to overgeneralize."

  3. #3
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    Quote Originally Posted by Doohickie View Post
    See in particur post 34:

    The small low voltage halogen bulbs have a reported life of 10 to 100 hours and that seems to be dependent on vibration level they are subjected to and luck.
    10h does not have much connection to reality. I could just overvolt a bulb right away and claim that the life varies between 3s and 100h. I ride really rough and my lifetimes have been in the region of 200h. 100-200h is plenty, equivalent to several years of riding for most people.

    In the particular case, though, I would worry that the standard dynamo would tend to underpower the lamp making the light excessively yellow and dim. However, at least there would be no need to employ a protective Zener.

  4. #4
    Gear Hub fan
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    How many volts is the Vistalite bulb? Give it a try with the dynamo as you normally cannot damage the dynamo. I would be surprised if it gives out enough light to actually illuminate the road adequately though.

    2_i;

    The hours I gave were listings frojm a web site with no other information given. If using an older headlight w/o overvoltage protection the life could be pretty short for a fast rider I understand. Some of the old dynamo setups were apparently pretty notorious for blowing bulbs at high speed.

    To maximize bulb life w/o adding zener diode protection the Shimano halogen bulb dynamo headlight uses a 9.6 volt 5 watt bulb. Normal German halogen dynamo lights use a 6V .4 Amp or .5 Amp halogen bulb so either 2.4 or 3 watts rating at a lower voltage.
    Gear Hubs Owned: Rohloff disc brake, SRAM iM9 disc brake, SRAM P5 freewheel, Sachs Torpedo 3 speed freewheel, NuVinci CVT, Shimano Alfine SG S-501, Sturmey Archer S5-2 Alloy. Other: 83 Colnago Super Record, Univega Via De Oro

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  5. #5
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    Quote Originally Posted by tatfiend View Post
    If using an older headlight w/o overvoltage protection the life could be pretty short for a fast rider I understand. Some of the old dynamo setups were apparently pretty notorious for blowing bulbs at high speed.
    Typical burn-out situation would have been that of riding downhill. That occurred, in particular, early on when halogens were introduced and the problem was not yet caught - regular incandescents were much more resilient with that respect. Subsequent halogen lamps both had the optics tailored to halogen bulbs and carried protectors. Still, though, the issue remained of the following avalanche effect. If the front bulb burnt out due to life, the load increased on the protector. Most could not withstand more than few minutes of increased load. After or even before the protector burnt out, the rear bulb would go. The rider would eventually change both bulbs, but now would be left without a protection.

    Depending on details of wiring the rear LED light can be still vulnerable if the front light ceased to take power for whatever reason. Typical rear light lacks an overvoltage protection.

  6. #6
    gna
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    Not to bring back this zombie thread, but I tried the halogen bulb and it worked, but it was rather dim. I believe Vistas were designed for 12V, and the bulb is rated for 5W, so the 6V 3W from my dynohub worked but was a bit underpowered. Reading the forum last night, I found this post, where funkystickman uses a LED halogen replacement. I thought I would try a similar, though smaller, LED bulb for an MR11 Halogen: http://www.dealextreme.com/p/mr11-1-...b-11-18v-91948

    Of course, I'm curious how much light it will produce at 6V and if it will work on AC. At worst, I'm only out $4. Anyone tried one of these bulbs?

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    I wouldn't bother with Halogens at this point. You only need two components to make your own LED dynamo light, ignore all those complicated circuits you find. You just need a 3 watt or more LED and a full bridge rectifier. You can get the full bridge rectifier at Radio shack. You can get the LED with reflector and everything by buying one of those "Tatical" LED flashlights. For instance, I went to Lowes and bought the Task Force 3w Cree Flashlight, took out all the battery driver circuity and just soldered the LED inputs directly to the outputs of the full bridge. It works just fine, barely even any flicker unless you are going slower than walking speed.

    To get a tail light I stuck a 3w LED to my back rack (with a heatsink) and wired it in series with the front. Now I have a 3W front and rear light.

  8. #8
    gna
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    Quote Originally Posted by siberia37 View Post
    I wouldn't bother with Halogens at this point.
    Thanks for the info, but I'm not bothering with a halogen. It's an LED bulb replacement for a halogen. I've built a few LED lights using a bridge rectifier, cap, and Cree Q5 or XR-E LED. Just thought I'd try to salvage this nice little light.

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