Another lighting question

Discussion in 'Australia and New Zealand' started by TimC, Apr 23, 2006.

  1. TimC

    TimC Guest

    A few weeks back, I got a few of those little frog type LEDs from PBK:
    http://probikekit.com/display.php?code=m1206

    Great, but they chew through batteries. The whites use 2 3V lithiums
    (very thin), and I didn't check what voltage they put out to the LED
    (presumably 3V or so, given the band gap needed to produce the blue
    part of the spectrum). At $7 a peice, and only seeming to last for a
    few tens of hours, that's $14 every few weeks per LED.

    OK, so goodie, I just constructed a battery holder for my two whites
    on the front of my helmet. A little heavy, but should work. My drill
    holls were small enough that it should even remain water resistant!

    OK, so damn, just opened the red one, and it's only 1 3V lithium,
    supplying 1.4V to the red LED, as expected. Anyone sacrificed their
    red led yet to find out whether the little IC in the resin is capable
    of voltage regulation, and hence whether the LED can be safely
    supplied with 6V?

    --
    TimC
    }> Is "wrongest" an actual word?
    } It's a perfectly cromulent word.
    Which, when used, embiggens us all.
    -- Jeff Ramsey, Steed and D. Joseph Creighton in ASR
     
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  2. Gags

    Gags Guest

    "TimC" <[email protected]> wrote in message
    news:[email protected]..
    > A few weeks back, I got a few of those little frog type LEDs from PBK:
    > http://probikekit.com/display.php?code=m1206
    >
    > Great, but they chew through batteries. The whites use 2 3V lithiums
    > (very thin), and I didn't check what voltage they put out to the LED
    > (presumably 3V or so, given the band gap needed to produce the blue
    > part of the spectrum). At $7 a peice, and only seeming to last for a
    > few tens of hours, that's $14 every few weeks per LED.
    >
    > OK, so goodie, I just constructed a battery holder for my two whites
    > on the front of my helmet. A little heavy, but should work. My drill
    > holls were small enough that it should even remain water resistant!
    >
    > OK, so damn, just opened the red one, and it's only 1 3V lithium,
    > supplying 1.4V to the red LED, as expected. Anyone sacrificed their
    > red led yet to find out whether the little IC in the resin is capable
    > of voltage regulation, and hence whether the LED can be safely
    > supplied with 6V?
    >

    I would guess that the red LED is probably only drawing about 30mA or so???
    If this is the case, just put a suitable resistor in series with it to drop
    the 6V to 3V at the light.....ie. R = V/I = 3/0.03 = 100 ohms. A 100 ohm
    resistor dropping 3V is dissipating 90mW of power so you could get away with
    a standard 0.25W resistor without any problems. I would solder it in-line
    with the wire and heatshrink over the top to keep it fairly water
    resistant......simple way to protect your "little IC in the resin"

    Let me know if you need a resistor, heatshrink, and a lend of a soldering
    iron.

    Gags
     
  3. flyingdutch

    flyingdutch New Member

    Joined:
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    you paid how much???

    I just picked up 10 reds, 10 whites plus a 5LED frontlight, delivered for $42
    from a guy in Melb off eBay. going well thus far

    PS batteries are available cheaper for em at DickSmith ($3-4 from memory)

    PPS that battery usage is silly-high imho. I need to change mine about every 3-6months during winter (i put em on frequent-flash setting, not solid unless searching for keys etc)
     
  4. TimC

    TimC Guest

    On 2006-04-23, Gags (aka Bruce)
    was almost, but not quite, entirely unlike tea:
    > "TimC" <[email protected]> wrote in message
    > news:[email protected]..
    >> OK, so damn, just opened the red one, and it's only 1 3V lithium,
    >> supplying 1.4V to the red LED, as expected. Anyone sacrificed their
    >> red led yet to find out whether the little IC in the resin is capable
    >> of voltage regulation, and hence whether the LED can be safely
    >> supplied with 6V?
    >>

    > I would guess that the red LED is probably only drawing about 30mA or so???
    > If this is the case, just put a suitable resistor in series with it to drop
    > the 6V to 3V at the light.....ie. R = V/I = 3/0.03 = 100 ohms. A 100 ohm
    > resistor dropping 3V is dissipating 90mW of power so you could get away with
    > a standard 0.25W resistor without any problems. I would solder it in-line
    > with the wire and heatshrink over the top to keep it fairly water
    > resistant......simple way to protect your "little IC in the resin"


    Hmm, when the LED is off, the full 6V would end up going into the IC
    -- dunno whether it would cope with that (it could do -- for all I
    know, the circuitry for the red and whites could be the same).

    > Let me know if you need a resistor, heatshrink, and a lend of a soldering
    > iron.


    Heh. I was an electronics geek once :) Although the heatshrink supply
    is getting low. And I came across some bad news last year -- EU
    regulations not allowing leaded solder anymore. Hello dry joints!


    Anyhoo, some slighly lateral thinking came to the rescue. Just tap
    the battery holder to give me 3V. It's ugly, probably fragile, but
    for the time being, works. I wonder how the heck how to waterproof
    the hole mess, and still be able to charge batteries?

    --
    TimC
    Just don't create a file called -rf. :)
    -- Larry Wall in <[email protected]>
     
  5. flyingdutch

    flyingdutch New Member

    Joined:
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    how much weight you intending on having on your head?
    with that overflowing brain, long hippy hair, industrial mount for the rear and now a veritable car battery for the LEDs your gonna end up with either a crook neck or one like Arny!

    F"EEts nudda doooomah"Dutch
     
  6. BrettS

    BrettS Guest

    flyingdutch wrote:

    > you paid how much???
    >
    > I just picked up 10 reds, 10 whites plus a 5LED frontlight, delivered
    > for $42
    > from a guy in Melb off eBay. going well thus far
    >
    > PS batteries are available cheaper for em at DickSmith ($3-4 from
    > memory)
    >
    > PPS that battery usage is silly-high imho. I need to change mine about
    > every 3-6months during winter (i put em on frequent-flash setting, not
    > solid unless searching for keys etc)


    My white one supposedly lasts 90 hours on slow flash, 40 hours on fast
    flash and 10 hours on solid. It takes 2 of the CR2016 button batteries.
    After paying $4.00 each for them at Tandy/Dick Smiths, I found that
    Jaycar have them for less than $3 each if you buy them in bulk. (8+)

    --
    BrettS
     
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