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Thread: All-in-one LED bike light for my commuter

  1. #1
    Join Date
    Oct 2012
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    San Antonio TX, USA
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    Default All-in-one LED bike light for my commuter

    last winter I felt the need for a non-flashing bar light on my commuter. I have a non-flashing light on my helmet (very helpful for the "please don't pull out and kill me" moments) and a flashing light on my bars, but the strobe effect on my bars is a bit distracting in the dark and a non-flashing bar light would get me more forward visibility and let me keep the attention catching flashing light.

    The mechanic at my local bike store also gave me the guts of a Lezyne all-in-one front light (battery is part of the light), so I'll be using the control/charging board from that, which simplifies things a bunch.

    anyway, design will be 2 LEDs in parallel (Cree XP-G2 and XP-L) with 10deg optics, the Lezyne Macrodrive board, 2 Panasonic NCR18650B batteries (~3400mAh each) in parallel, momentary switch at the back. One cavity on the front for the LEDs with a nice thick piece of lexan, which should also give some side lighting. One cavity underneath for the batteries and driver.

    Squared up a nice piece of alu to the right size last night with my facemill (about to start the larger side)


    and bevelled the edges with a 90deg router bit


    next up is drilling the holes for the charging port and switch, then starting on the LED cavity

  2. #2
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    Jan 2003
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    Deep in the Heart of Texas!
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    I can almost see it appearing before my eyes.

  3. #3
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    Sep 2004
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    Oregon Coast
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    Quote Originally Posted by CCWKen View Post
    I can almost see it appearing before my eyes.
    What are you drinking?
    _____________________________________________
    Mel Larsen
    I would rather have tools that I never use, than not have a tool I need.

  4. #4
    Join Date
    Oct 2012
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    San Antonio TX, USA
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    I think I need your eyes - my brain hurts after working out the plans

  5. #5
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    Oct 2012
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    finished the back end - hole for a charging cable and switch, plus some grooves for water breaks and cooling


    cut off the excess material at the front of the light using the bandsaw


    cut the overhang to size and the recess for the lexan front plate


    now need to grind a face grooving cutter for the o-ring grooves and bore the recesses for the LEDs

  6. #6
    Join Date
    Dec 2015
    Location
    Chilliwack, BC, Canada
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    As an ex bicycle commuter I'm really looking forward to seeing your final product.

    You mention running the two LED's in parallel. If you intended to say that then let's start by saying that it's not a good idea to run LED's in parallel due to how they behave. Each needs its own current driver or current limiting source. Does that Lezyne board have two outputs for separate LED's?

    A quick check shows that the Cree LED is just the light producing LED by itself. And a quick look for Lezyne macro drive shows that you've likely scavenged the board from an existing bicycle light. And if that's the case it can only drive one LED from the one output. You'd need a separate board for the second LED. And what is the board set up to supply to the LED for output current? The Cree unit is listed as up to 1500ma. If the original light did not support that high a current and it is only putting out some lower value you likely won't see a big improvement over the old light.

    Or did you figure this all out already and just put the short version in your post?

  7. #7
    Join Date
    Oct 2012
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    thanks! The answer to your Q is the last bit you wrote

    You're right that generally speaking putting LEDs in parallel is not a great idea as any difference in Vf between them at the drive current can lead to one LED being driven harder and potentially going into thermal runaway. However, in practice I've never heard of anyone having problems with that in the 18 or so years I've been building lights and the original Lezyne light the board came from has 2 Cree XP-G2 LEDs in parallel (one board, 2 LED pads connected in parallel). They're also not going to be driven all that hard at a max of 1A each out of a manufacturer recommended limit of 1.5A for the XP-G2 and 3A for the XP-L2.

    So, we'll see how it goes. If there are problems I can swap out the driver for a custom board I had made a while back that has 2 separate outputs, but it would be nice to avoid that as the Lezyne board is both the driver and charger.

    A couple of my rides home every week are now ending in darkness, so I need to keep pushing this along. Hope to get some more done tonight.

  8. #8
    Join Date
    Oct 2012
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    did the layout for the LED recesses and o-ring groove


    and ground a broken 2mm endmill () into a face grooving tool


    however I ran out of both clearance between the tool and the overhang and energy, so I'll grind the tool down to fit, hopefully tonight.

  9. #9
    Join Date
    Dec 2015
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    Chilliwack, BC, Canada
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    ....and the original Lezyne light the board came from has 2 Cree XP-G2 LEDs in parallel (one board, 2 LED pads connected in parallel).
    Well, that certainly takes care of my concerns! It also shows that any variation is a very small and inconsequential issue. And I find that both a little amazing and fantastic that they can do that all at the same time.

    I retired back when white LED "emitters" were just coming out for use in bicycle lights right at the end of my working days. So most of my experimentation was related to halogen bulbs and better battery packs... And no LiPo packs either. Just some of the then slightly stronger NiMH cells. I missed out on all the fun ! ! ! ! I'm looking forward to seeing how all the tease photos come together for the final product even more now.

  10. #10
    Join Date
    Jun 2013
    Location
    Lancaster County PA
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    367

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    Cool project, I'm anxious to see the end product.

    Dwight

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