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# i'm trying to make a light for my bicycle using a
3w luxeon led (maybe x3) but its giving me a headache
i can build things but electric doesnt agree with me... (my hair is constantly pointing up to this day!)
apparently resisters use up enegery? there is a product called a buckpuck which has chips and buttons and costs more than i want to pay :p

edit : found this... ebay link

edit 2 : so far i have nothing - im planning it (i can get a 12v 8amh battery for £15 from work) but they don't sell the bulbs
I was looking at using a mr16 (gu5.3) light bulb holder and bulb, but then i stumbled across luxeon led mr16s! but i don't think they've got the regulators built in? (or i've found a place (farnells) where you can buy the compenents (at a hefty price) to built your own 50mm x3 luxeon light)
oh yea how rude - thank you for your reply :D
(I helped save b3ta! SkUG >_O i got a couple of stitches in my eyeball... ow, Sun 27 Jan 2008, 16:48, archived)
# Ahhh, LED power
As it happens I know a geekily large amount about this.

Any linear current limiter (resistor, linear regulator and resistor, regular constant-current source) will waste energy... if your LED breaks down at 3V and you're using a 12V battery, you are throwing away at least 75% of your power.

You need a switched-mode (bucking) power supply that makes *just* slightly more than the LED breakdown voltage, and then a very small series resistor to limit current and protect the LED. The best way to do it is to use the resistor as a current sense so that the supply makes whatever voltage is required for your desired current.

There's plenty of handy chips around, but building your own is definitely going to get into surface mount electronics teritory.



Might be easier to buy a light ;o)

hth.
(I helped save b3ta! Funkster, Sun 27 Jan 2008, 17:19, archived)
# thanks - this is true... but they're £300 and sum of parts costs about £30
so you can see why i'd rather make my own?
its 12v 3w
i'll get some links of what i propose to use (cheaper on ebay!)
please hold - thank you for your indepth reply - woo!
battery
bulb ideally 10degree beam
and i've got a bulb holder (from a broken light) - i'm wondering if that bulb has a regulator in it or if the transformer would have it? (as im not using the transformer!)
edit : i haven't done surface mounted circuitry since i was at school! mmm acid bath
(I helped save b3ta! SkUG >_O i got a couple of stitches in my eyeball... ow, Sun 27 Jan 2008, 17:29, archived)
# Looks like all you need is that bulb.
It has a wide-range (11 - 16 V) input so it obviously already has some kind of current limiting in it. As the 3 LEDs are no doubt in series, even if they're using linear regulation it'll still be about 75% efficient in terms of getting power to the LEDs.

Problem solved!

Mmmmm acid bath.
(I helped save b3ta! Funkster, Sun 27 Jan 2008, 17:44, archived)
# ahh i was wondering about that
so in theory
battery - switch - bulb holder - that led/bulb is all i need?
(I helped save b3ta! SkUG >_O i got a couple of stitches in my eyeball... ow, Sun 27 Jan 2008, 17:50, archived)
# Yep, that should be dandy.
(I helped save b3ta! Funkster, Sun 27 Jan 2008, 17:53, archived)
# otherwise its
battery, switch, 3 led, lenses, 3 x that board and something to put it all in
(I helped save b3ta! SkUG >_O i got a couple of stitches in my eyeball... ow, Sun 27 Jan 2008, 17:59, archived)
# That board...
... will drive three one-watt LEDs in series if you're using a 12V source, so you only need one.
(I helped save b3ta! Funkster, Sun 27 Jan 2008, 18:12, archived)
# ahah!
you sir are a geniearse! genius! o0o morris 8 - i'm building something that'll keep up with that! V-twin motorbike powered Austin 7!
(I helped save b3ta! SkUG >_O i got a couple of stitches in my eyeball... ow, Sun 27 Jan 2008, 18:17, archived)
# oo I like the sound of that!
Send photos, my Dad will love it as he had a fairly hopped up '7 special as his first car :o)

btw, you've just challenged me to a race and the morris is going to get quicker this year ;o)
(I helped save b3ta! Funkster, Sun 27 Jan 2008, 18:41, archived)
# While I'm here...
... know any good web hosts?

I need php5, an sql database, a couple of hundred meg of space, and a moderate amount of bandwidth... from someone reputable.
(I helped save b3ta! Funkster, Sun 27 Jan 2008, 17:46, archived)
# actually no i don't
but im sure some other b3taians will know (have you seen my website? no hosting at all - lol)
(I helped save b3ta! SkUG >_O i got a couple of stitches in my eyeball... ow, Sun 27 Jan 2008, 17:48, archived)
# Dreamhost
are cheep and pretty good. I use them to host fairly big stuff like Kittenwar, and lots of smaller stuff too. Referral linky.
(tomsk, Sun 27 Jan 2008, 18:15, archived)
# Cheers.
I like the way their splash page has a picture of a seemingly-dead fat kid on it ;o)
(I helped save b3ta! Funkster, Sun 27 Jan 2008, 18:43, archived)
# Yes, they kill a fat kid for every ten
new sign-ups, it's a great marketing incentive.
(tomsk, Sun 27 Jan 2008, 19:02, archived)