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  1. #1
    Burning Matches. ElJamoquio's Avatar
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    So, today in Michigan it's snowing fairly quickly, and I test-ran my first commute; I plan to start commuting by bike on Monday in earnest.

    I bought a Nitehawk Raptor - 10 W - and it seems to be pretty good in terms of light. I'm about halfway through the Geek thread, and I'm already thinking of replacing it with some sort of Luxeon LED M16 setup.

    However, I was hoping to power it with only 6 volts. What's the easiest/best solution? My first thought (as a mere *mechanical* engineer) was that there would be a simple resistor in there (which slvoid seems to say is the case with some Cateye products) - and I could reduce the resistance, pop everything back together, and be off and running.

    I should mention that I was hoping not to pay the $130 for a whole 3W LED system from Cygolite - and I don't even know if that system is 6V.

    Should I disect a flashlight? Some other solution?

    BTW, thanks to everyone for making the commuting forum such a success - the lightchart Excel spreadsheet, the beginning commuters, and the geek threads were invaluable.

  2. #2
    Senior Member
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    Paying $130 for a 3W LED system is really overkill. 3-watt Luxeon Stars cost less than $20 and have a Vf of like 3,4 volt (white). Can definitely be driven by 6V, even 4.5. Driving them is really easy, if you don't care about nuking away some power as heat. Just do a LED series resistor calculation like you would do with any other LED, but keep resistor heat margins and LED current margins generously large.

    Want to be more effective? There's always buck-dump inductive drivers but it requires knowledge, some effort and a microcontroller.

    http://www.microchip.com/stellent/id...pnote=en012124

    if you need more help just let me know. I'm studying EE and pretty interested in LED applications

  3. #3
    Burning Matches. ElJamoquio's Avatar
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    Quote Originally Posted by grapetonix
    Paying $130 for a 3W LED system is really overkill.
    Yeah, that was basically my point - I didn't want to spend that much.

    Another question - I was hoping to power it with 5 Ni-Cd batteries - does anyone have the discharge rates curve for Ni-Cd batteries?

  4. #4
    Senior Member ken cummings's Avatar
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    Quote Originally Posted by grapetonix
    Paying $130 for a 3W LED system is really overkill. 3-watt Luxeon Stars cost less than $20 and have a Vf of like 3,4 volt (white). Can definitely be driven by 6V, even 4.5. Driving them is really easy, if you don't care about nuking away some power as heat. Just do a LED series resistor calculation like you would do with any other LED, but keep resistor heat margins and LED current margins generously large.

    Want to be more effective? There's always buck-dump inductive drivers but it requires knowledge, some effort and a microcontroller.

    http://www.microchip.com/stellent/id...pnote=en012124

    if you need more help just let me know. I'm studying EE and pretty interested in LED applications
    So nice to see someone who knows the real nitty gritty of light systems. Could we go to www.alliedelec.com and just buy some of those Luxeon LEDs, a holder for them, and the electronic widgets you mentioned? Maybe just put 2 in series. A little under-driven perhaps but less heat loss.
    Perhaps some of the multi-LED arrays woudl give as much l;ight and be far more efficient. I bow to your wisdom.
    This space open

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