[Noisebridge-discuss] cheap LED power & boost converters Re: driving multiple LEDs with minimal batteries

[jim]

   note that this is not a power converter. if you use a 
booster to get higher voltage, you get fewer amps, and 
the power is about the same. 
   a particular LED has its specific voltage and current 
requirements. current times voltage equals power. more 
of the same LED requires the same voltage but more 
current (e.g. using four LEDs that each needs two volts 
and 10 milliamps requires a power supply that provides 
two volts and 40 milliamps). 
   the more power you need, the bigger the battery (or 
the greater the number of batteries). power requirements 
roughly equate to size and weight requirements. 
   different types of LEDs have different voltage and 
current requirements. if you use multiple different 
types of LEDs, the power supply may need some parts to 
accommodate each of the different types, i.e. more 
size and weight affect to the overall circuitry. 
   judiciously choosing which LEDs and how many to use 
lets you approach an overall design that doesn't present 
power supply demands that wreck the aesthetic. knowing 
the LED specs and using a little arithmetic will help. 





On Tue, 2011-01-04 at 22:41 -0800, T wrote:
> 
> 
> The circuit that gives you more volts from a lower voltage supply is
> called a "boost" converter.  Typically it makes pulses through an
> inductor so more amps at less volts come out as more volts as fewer
> amps.  
> 
> 
> I'd start
> here: https://secure.wikimedia.org/wikipedia/en/wiki/Boost_converter
> 
> 
> Cheap mass produced devices with boost converters that maybe could be
> adapted to your purposes include those LED flashlights that run on a
> single AA or AAA cell (market price for a 1-watt 1-AA flashlight seems
> to be about $20) and those single-AA "emergency" cell phone chargers.
>  I have no idea how much power they can handle or how long they can
> run.  But they are cheap at places like Fry's and EBay.
> 
> 
> 
> If I was doing it, I'd get a 1-watt 1-AA flashlight and user optical
> fibers (get a 1970's "light sculpture" at a thrift store) to deliver
> the light to many little points.  That way you don't have to deal with
> the electronics at all.  Unless you want them to blink or something.
>  In that case an Arduino and and an inductor and a capacitor would let
> you do both the blinking and the boosting under programmatic control.
> 
> 
> BTW, for people looking for a lot of light in a small flat package for
> pretty cheap, halted has 12V 1-watt pre-built circuits for $9.95.
>  They are less than one square inch.  Add one of those little sub-AAA
> 12V camera batteries and you have a lot of light in a little package.
>  I bought one in white and one in red at the Santa Clara store.  Hours
> and locations: http://www.halted.com/commerce/info/contactinfo.jsp
>  You might also be able to get them online.
> 
> 
> Best Regards.
> 
> 
> On Tue, Jan 4, 2011 at 12:06, meredith scheff <satiredun at gmail.com>
> wrote:
>         I'd like to do a soft circuit scarf or three, but I'm always
>         running up against the problem of power. I usually use fairly
>         low power LEDs 
>         (<2v) driven by a 9v battery or one of sparkfun's LiPos. 
>         I've heard tell of somehow being able to power more, but I'm
>         still learning this EE stuff. Could some kind person point me
>         in the right direction?
>         Meredith
>         
>         -- 
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