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  1. #1
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    LEDs to replace bulbs in a bottle generator system

    The bulbs in a traditional 6v 3w bottle generator bike lighting system are:

    6v 3.0w 0.5a headlight only (or)

    6v 2.4w 0.4a headlight
    6v 0.6w 0.1a taillight

    I want to replace bulbs with these three specs with suitable LEDs.
    How do I determine which LEDs to use, and how do I match them to
    the generator so they will work. I would like to generate as much light
    as possible, but I realize that is a secondary goal. Which LEDs should
    I purchase for each of these, and how do I match them to the generator
    by the selective use of appropriate resistors?

    Sources for the LEDs would also be appreciated.

    Thanks much for your help.

  2. #2
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    I think you need to do some reading of the forum, this isn't always simple.

    Bottle generators usually produce ac, which is fine for filament bulbs. However, LEDs need dc. There are some LED headlamps which rectify the input, but they aren't cheap. I believe B&M produce at least one model.

  3. #3
    Scott n4zou's Avatar
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    Here are some circuits for using LED's with a dynamo.
    http://www.pilom.com/BicycleElectron...moCircuits.htm

    The above circuits have been around for a few years now. They also do not require batteries. I personally do not like my headlight and taillight going out when stopped. I added batteries to my system so my headlight and taillight continue to illuminate at stops. These are Ni-MH AA 1,800mA hour batteries. If the batteries are fully charged they will power my lights for at least 3 hours without the dynamo engaged. I selected a Luxeon 1-watt LED rated for 350mA and a 5000 mcd 10mm red LED in my taillight. It's rated for 36mA but I set the current for 30mA with a 100-ohm resistor. My resistor for the headlight is measured at 4.9-ohms. I simply used a 5.1-ohm resistor and parallel 50-ohm resistors until the current through the LED measured with a milliamp meter read 350mA with a fully charged batteries, the dynamo engaged, and riding at 10 MPH where the dynamo is producing maximum current. My resistor consists of one 5.1-ohm resistor and three 50-ohm resistors in parallel. According to the wire used to hook everything up will determine the resistance required for your setup. You'll just need to experiment and find the required resistance for your setup. I chose these components for a reason. With the dynamo engaged, LED's turned on, and traveling at 10 MPH or higher 120mA of excess current produced by the dynamo is recharging the batteries. This is the suggested slow recharge rate for Ni-MH batteries. When you open the LED switch turning off the LED's the full 500mA current will flow into the batteries. This is the suggested rapid recharge rate for Ni-MH batteries so if you completely discharge your batteries you can easily recharge them during the day with your dynamo. This is very handy when touring where you would not have power available or you did not carry a battery charger to recharge them from the utility power grid. I chose to use 4.8-volts with the batteries regulating the voltage to ~5.2-volts as this voltage conforms to USB standards. I installed a USB connector so I could power and recharge a GPS unit with the dynamo and Ni-MH batteries. Here is the circuit I use.


    I ordered my 1-watt LED and matching Fraen 10X20 elliptical holder and lens from here.
    http://www.luxeonstar.com/index.php

    I just put the red 10mm LED in the taillight where the .6-watt bulb was. I built my LED and optics in a 1-inch PVC pipe coupler available in the plumbing section of any hardware or building supply store. A prescription bottle cap with the selectable child-proof/easy open cap is used to hold a clear plastic cover over the front of the lens to protect it. A scrap of aluminum used as the heat sink was cut to fit in the PVC pipe coupler and RTV sealed the rear of the optics and LED.

  4. #4
    Senior Member saturnsc2's Avatar
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    Quote Originally Posted by ackptui View Post
    The bulbs in a traditional 6v 3w bottle generator bike lighting system are:

    6v 3.0w 0.5a headlight only (or)

    6v 2.4w 0.4a headlight
    6v 0.6w 0.1a taillight

    I want to replace bulbs with these three specs with suitable LEDs.
    How do I determine which LEDs to use, and how do I match them to
    the generator so they will work. I would like to generate as much light
    as possible, but I realize that is a secondary goal. Which LEDs should
    I purchase for each of these, and how do I match them to the generator
    by the selective use of appropriate resistors?

    Sources for the LEDs would also be appreciated.

    Thanks much for your help.
    just visit peter white cycles. they specialize in dynamo lighting systems. they sell led taillights & headlamps with the standlight features. look for the new B&M led fly iq light. it's the brightest dynamo light to date. it blows away the halogen lights by far! it uses a high power luxeon led. they also have a high power 12 volt 6 watt halogen dynamo set...
    "DO IT IN A SATURN!"

  5. #5
    rhm
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    Yes, but what about these?
    http://superbrightleds.com/other_bulbs.htm


    PR2-WHP 1 Watt Flashlight Bulb

    Flange base flashlight bulb with 1 Watt High Power White LED
    Wide voltage range will operate from 2.8 to 12VDC , 80~550ma
    35 lumen, 30 degree beam pattern, bottom contact must be connected to positive

    Does anyone know if this will fit in a bicycle headlamp designed for a 6 v halogen bayonet bulb?

    OR:

    Miniature 10mm screw base bulb with 1 Watt High Power White LED
    Wide voltage range will operate from 2.8 to 12VDC , 80~550ma,
    35 lumen, 30 degree beam pattern, bottom contact must be connected to positive

    Is this (10 mm) the same socket size as dynamo lamps use? If so, couldn't you wire it so the positive current alternates between the head light and the tail light? If so, you wouldn't even need a bridge rectifier....

    For comparison's sake, does anyone know how much light (in lumens) a typical bottle dynamo light emits?
    Last edited by rhm; 12-04-07 at 08:02 AM. Reason: (1) Found more stuff to include, (2) switched the photos

  6. #6
    Scott n4zou's Avatar
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    Quote Originally Posted by rhm View Post
    Yes, but what about these?
    http://superbrightleds.com/other_bulbs.htm


    PR2-WHP 1 Watt Flashlight Bulb

    Flange base flashlight bulb with 1 Watt High Power White LED
    Wide voltage range will operate from 2.8 to 12VDC , 80~550ma
    35 lumen, 30 degree beam pattern, bottom contact must be connected to positive

    Does anyone know if this will fit in a bicycle headlamp designed for a 6 v halogen bayonet bulb?

    OR:

    Miniature 10mm screw base bulb with 1 Watt High Power White LED
    Wide voltage range will operate from 2.8 to 12VDC , 80~550ma,
    35 lumen, 30 degree beam pattern, bottom contact must be connected to positive

    Is this (10 mm) the same socket size as dynamo lamps use? If so, couldn't you wire it so the positive current alternates between the head light and the tail light? If so, you wouldn't even need a bridge rectifier....

    For comparison's sake, does anyone know how much light (in lumens) a typical bottle dynamo light emits?
    These will work but you will need a bridge rectifier circuit between the dynamo and that light. A bicycle dynamo produces AC current and these LED replacement lights need DC current. Maximum current for a typical dynamo is 500mA and as these are rated for a maximum of 550mA you should be ok. These lights are only rated at 35 Lumens. New LED's from Cree and Luxeon are rated at 80 Lumens in the 350mA current range and can be driven with 500mA with only a slight decrease in life.


    Not all dynamo lights produce the same light output. There are cheap dynamo lights that are not bright at all and burn for only a few hours like flashlight bulbs. There are also expensive halogen dynamo bulbs that last many hours with exceptional beam patterns producing lots of usable light.

  7. #7
    rhm
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    Quote Originally Posted by n4zou View Post
    These will work but you will need a bridge rectifier circuit between the dynamo and that light. A bicycle dynamo produces AC current and these LED replacement lights need DC current. ....
    Thanks for your reply, and all the information! But please consider this: Let's say I wire the lamps without a bridge rectifier, so the wire goes to the positive terminal of the headlight and the ground goes to the positive terminal of the tail light; then the AC current would alternate between the head and the tail lights. There would be a flickering effect at low speed (bicycle dynamo lights always flicker, but this would flick more). Would it work? Would it damage the LED's?

  8. #8
    Scott n4zou's Avatar
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    Quote Originally Posted by rhm View Post
    Thanks for your reply, and all the information! But please consider this: Let's say I wire the lamps without a bridge rectifier, so the wire goes to the positive terminal of the headlight and the ground goes to the positive terminal of the tail light; then the AC current would alternate between the head and the tail lights. There would be a flickering effect at low speed (bicycle dynamo lights always flicker, but this would flick more). Would it work? Would it damage the LED's?
    There will be flickering at slow speeds but the serious problem this will cause is the reverse current when the AC wave is going negative. These LED's may not tolerate any reverse voltage. The diodes used in a rectifier are made to block high voltage so no damage is done. An LED is made to emit light when passing current and is not made for blocking current. If you force it to block reverse current additional heat will be generated which will burn out the LED. You can purchase them as a single component. Radio Shack has a suitable bridge rectifier that will work fine except it will not be as efficient as using four 1n5818 diodes. The part number is 276-1152.
    http://www.radioshack.com/sm-1-4a-10...i-2062581.html



    Only one wire is marked with a + sign. This is the wire that will connect to the positive (+) lead of an LED. The wire opposite the + marked wire is the negative lead and connects to the negative (-) lead of the LED. The other two wires are connected to the dynamo and it makes no difference which one is connected to the dynamo output terminal. The other wire will connect to the bicycle frame as the dynamo uses a frame ground for the other connection. This requires you keep both positive and negative DC wires isolated from the bicycle frame. This will cause a problem when trying to use an LED replacement bulb in a dynamo light. The fix for this problem is to mount the headlight to the bike with a plastic clamp so the headlight is isolated from the bicycle frame. After you do this all you do is run the negative wire from the rectifier to the isolated mounting bracket on the light.

  9. #9
    d_D
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    Another issue with leds is they tend to be a lot more directional than a bulb.
    The screw in led above has a 30 degree beam pattern. Stick one in a bicycle headlight and some parts of the reflector are not going to have any light to reflect. This might make the beam pattern quite a bit different with an led compared to a bulb.

  10. #10
    Senior Member saturnsc2's Avatar
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    umm...if your planning on using an led where a halogen bulb's supposed to be you probably will have a problem with the beam. the light source from a halogen bulb is in a different place than an led & the reflector is designed for the halogen bulb. i just bought the new B&M led iq fly light & it produces a very bright wide beam of 40 lux which is way more brighter & wider than the halogen lights. they however use special optics to produce the wide bright beam. the light i speak of is on this site: http://www.bumm.de/index-e.html save yourself all the aggravation trying to make an led light out of a halogen light & just buy this light. you won't be sorry....
    "DO IT IN A SATURN!"

  11. #11
    rhm
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    Quote Originally Posted by saturnsc2 View Post
    umm...if your planning on using an led where a halogen bulb's supposed to be you probably will have a problem with the beam. The light source from a halogen bulb is in a different place than an led & the reflector is designed for the halogen bulb.
    Granted.
    Quote Originally Posted by saturnsc2 View Post
    i just bought the new B&M led iq fly light & it produces a very bright wide beam of 40 lux which is way more brighter & wider than the halogen lights. they however use special optics to produce the wide bright beam. the light i speak of is on this site: http://www.bumm.de/index-e.html
    Certainly an interesting light. Where did you get it? What are its voltage tolerances?
    Quote Originally Posted by saturnsc2 View Post
    save yourself all the aggravation trying to make an led light out of a halogen light & just buy this light. you won't be sorry....
    Thanks; this is, no doubt, good advice! But remember the title of this thread. Personally, I'm not using a bottle generator, but want screw-in LED bulb for my wife's 1966 Raleigh RSW-16 with its dynohub and lamps built into the fenders. I'm willing to put a bridge rectifier into the circuit somewhere, there's plenty of room for it in the headlamp; but anything more radical would compromise the classic look of the bike.

    As for the Busch & Muellers... well, I've had very bad luck with their stuff, and it ain't cheap. I've fried two DToplights / Standlights for no evident reason, and have no idea how to fix them, or even diagnose the problem. I fried a similar Spanninga light too (not so hard to diagnose: the LED melted off its leads, and was rattling around inside the unit!). And all that was before I rebuilt my Nexus dynamo hub into a 16" wheel, which now puts out 12 to 15 volts at moderate speed (so I'm running 12 V 5W halogen with some success). If anyone knows of an LED headlight that'll handle that kind of voltage, let me know.

    No need to recommend a Schmidt SON20, I know about 'em. It's just not what I want.

  12. #12
    Scott n4zou's Avatar
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    Quote Originally Posted by iwico View Post
    Hi

    Please remember LED same time is a diode. You do not need DC first. Just place LEDs at the place normal diodes are (of course make sure join a resistor). the LEds will be lit.

    See my dynamo on www.freelights.co.uk
    There both diodes but rectifier diodes are made for blocking reverse current, LED's are not! There just made to produce light. Cree and Luxeon LED's will not handle any reverse current and will quickly burn out when subjected to AC current. The LED's in your blinkie will handle low current produced in your system but not the 500mA produced by a bicycle dynamo.
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    Also, when working with high-powered LEDs, you'll probably need to investigate the proper amount of heat-sinking that's needed to keep the LED under a safe temperature (<150 degrees C is typical).

    I am guessing that the superbrightleds.com PR-style 1W LEDs will fit anything that takes a PR bulb, and does not have heatsink issues. Sure, the beam shape may be different due to LED directionality. FWIW, Terralux sells a 1 W LED that puts out 50 lumens.
    Same roads, same rights, same rules.
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  14. #14
    Scott n4zou's Avatar
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    Quote Originally Posted by rhm View Post
    I rebuilt my Nexus dynamo hub into a 16" wheel, which now puts out 12 to 15 volts at moderate speed (so I'm running 12 V 5W halogen with some success). If anyone knows of an LED headlight that'll handle that kind of voltage, let me know.
    This LED will work.
    http://www.dealextreme.com/details.dx/sku.2394
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  15. #15
    Zoom zoom zoom zoom bonk znomit's Avatar
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    Check out: http://www.pilom.com/BicycleElectron...moCircuits.htm for a range of circuits for dynamos.
    No, in general there is no drop in replacement for the typical 3w halogen bulb/reflector setup, but you can get a single led and optic for around 10$ which will be as good or better than the original, or you can go silly and build super bright multi LED lights.
    I just built a 5w triple LED setup that gives the equivalent light of a 15-20w halogen.

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