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LED Bike Headlight

Discussion in 'Electronic Basics' started by browntimdc, Aug 20, 2003.

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  1. browntimdc

    browntimdc Guest

    Just finished throwing together a light for my e-bike today. I used 18
    of the 8000mcd white LEDs from lsdiodes.com. Three strings of 6 LEDs.
    Each string has an LM317L to regulate current to approx. 22mA with a 56
    ohm resistor. Reaches full brightness at approx. 22V. Run off my 24V 8AH
    main battery. It's always lit when the bike is on: DRL.

    Photo: http://home.flash.net/~brownt/jpg/PICT5094s.JPG

    Tim
     
  2. Linear regulators may be quite lossy but its big enough battery guess.
    Couple of things might interest you:

    www.candlepowerforums.com if you wnat to wring the last out of batteries
    these guys wil help.

    and the bike current mailinglist, link escapes me at mo.

    Adam
     
  3. 24V 8AH on a bicycle? That's nuts!

    I hope it's not an expensive SLA. I've never had one of those survive
    bicycle use for more than a few months. They'd become an open circuit
    somewhere out in the middle of nowhere at night. I switched to NiMH
    because they are lighter, cheaper, and much more reliable for 24 to 48
    W/hr packs.
     
  4. I presume there's an electric motor on there somewhere as well as the
    LEDs. ;-)

    Best regards,
    Spehro Pefhany
     
  5. Frank Miles

    Frank Miles Guest

    I've used the same 12V 7AH SLA on my commuter bike for some years now.
    No motor, just lots of light. Replaced a NiCd system. Of course, this is
    used in fairly mild winters, temperatures usually not dropping much below
    0degC.

    -frank
    --
     
  6. Tim Brown

    Tim Brown Guest

    I measured these at 3.3V @ 20mA. So, you're suggesting that the LED
    forward drop will increase over time?

    Tim
     
  7. Jim Yanik

    Jim Yanik Guest

    (Tim Brown) wrote in
    No,there's a variation in LED Vf from LED to LED.
    They all do not have the same Vf.Some will be 3.2Vf,some 3.9VF....
     
  8. I think these are lower-voltage-drop-than-average white LEDs. I do not
    expect the voltage drop to increase with time.

    - Don Klipstein ()
     
  9. Tim Brown

    Tim Brown Guest

    The point is I checked several LEDs, I checked each of my 3 strings
    for total drop and the light works fine. I took Watson to mean that he
    thinks I'll have trouble later. I'm well aware there is part to part
    variation in voltage drop. If I were making a bunch of these lights
    maybe I'd just use 5 lamps in a string or screen parts.

    As it is I made a headlight for my electric bike and it works fine. I
    thought I would just share the idea and a source of good, cheap LEDs.
    I didn't come here to be challenged on every detail and lectured about
    things I already understand. Good bye.

    Tim
     
  10. My experience is that better ones over the past 2 years had a voltage
    drop averaging .1-.2 volt more than the voltage drop of older models
    from 5-6 or so years ago. I remember back when an average Nichia white
    or blue LED had a typical voltage drop of 3.4 or 3.5 volts.
    Of course the light output doubled or more over these several years...
    I remember Nichia's NSPW500BS having a typical "beam candlepower at 20 mA"
    (my words) close to 2,000 mcd several years ago, and then it went to about
    4,000 and then 5,600 and now it's 6,400...
    But despite personally seeing long term positive correation between
    voltage drop and efficiency for a given color and chemistry, I hear
    enough about a negative correlation in that area in a short term.
    Supposedly "duds" that also have unusual voltage drop further also have
    unusually high resistance that makes unusual voltage drop being in the
    upward direction. I see a few the other way, by being "duds" that have
    partial shorts such as from static damage (mainly from static-sensitive
    GaN and InGaN chemistries).

    - Don Klipstein ()
     
  11. What seems strange to me is that Nichia hasn't changed their parts
    numbering to show that improvement. And when I bought some recently,
    they showed no indicator in the part number of what the rank is. The
    original batch I got was rank S, the latest rank R. To me it would
    seem best if the customer had a choice. Of course they would have to
    charge more for higher ranks, but why not.

    I noticed that some cheaper blue LEDs I got from Futurlec have dies
    that aren't centered in the middle of the leadframe. Seems that if
    you get a 'good price' on an LED, you're usually getting a second, not
    a prime part.


    --
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    ###Got a Question about ELECTRONICS? Check HERE First:###
    http://users.pandora.be/educypedia/electronics/databank.htm
    My email address is whitelisted. *All* email sent to it
    goes directly to the trash unless you add NOSPAM in the
    Subject: line with other stuff. alondra101 <at> hotmail.com
    Don't be ripped off by the big book dealers. Go to the URL
    that will give you a choice and save you money(up to half).
    http://www.everybookstore.com You'll be glad you did!
    Just when you thought you had all this figured out, the gov't
    changed it: http://physics.nist.gov/cuu/Units/binary.html
    @@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@
     
  12. Actually, you missed the point, almost entirely. You posted an
    interesting message on a subject that generated a pleasant discussion,
    between people of varying levels of education, on this topic. That
    indicates that it was a good topic for these groups. Very little of
    the traffic was directly about or for you, but about other people
    thinking (and, perhaps, making mistakes) and learning from your post
    and the discussion generated by it. Your first paragraph, here is
    also a good addition to that discussion.

    Please don't go away mad. This thread is a good example of what this
    group was created to do.
     
  13. I have also noticed this.
    Look for latter part of the lot number on the sticker/label on the
    antistatic bag (if you actually got them from Nichia). The latter portion
    of the lot number is a combined color and "beam-candlepower" brightness
    ranking assigned to that lot.
    For types that usually fall close to the border between ranks, you can
    easily get some of the higher rank and then some of the lower rank. My
    experience with many small quantity purchases for prototyping jobs is that
    when you get shipped alternating-back-and-forth-rank LEDs, all of them
    are not far from the border between ranks.
    A lesser aspect of Japanese manufacturer culture?
    Really badly noticeable such misalignment is not typically Japanese and
    is arguably subpar from places other than Japan but near the "east coast"
    of Asia.

    - Don Klipstein ()
     
  14. Guest

    Guest Guest


    Cool!

    In working with motors my experience is that they suck lots of current on
    startup and can cause battery voltage to drop.
    With the amount of regulation you are using; do you have any problems with
    brightness change during accelaration?

    Strill
     
  15. Ron Hubbard

    Ron Hubbard Guest

    Just out of curiosity, where did you get the carbon fiber
    from?

    Kevin McMurtrie wrote in message ...
    it's on.
     
  16. Tap Plastics <http://www.tapplastics.com/>

    Tap Plastics is mostly a SF Bay Area business but they do web orders
    too. They're always on my list of places to shop when gathering project
    materials.
     
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