[Noisebridge-discuss] driving multiple LEDs with minimal batteries

Taylor Alexander tlalexander at gmail.com
Thu Jan 6 13:00:04 PST 2011


Hey. I just signed up for the mailing list (i've been on the useless digest
format for years, finally switched to the individual mails) just to I could
help here. First of all, am I responding right? Do I just hit reply all? I'm
new to the whole mailing list concept.

As far as LEDs, I do plenty of PCB design in EAGLE and have been playing
with high current LED driver circuits lately. I just made a board with 4
CREE XP-G LEDs that each are driven at about 800mA. The whole board draws
about 10w and puts out as much light as a 60w bulb! Gets pretty hot too...

I've recently set up my whole lab downstairs for SMT soldering, with a nice
microscope, hot air system, and all the bits and pieces I need for
soldering. Its pretty awesome!

I haven't read all the e-mails in this thread as they were all mixed in with
the digest till i switched it over an hour ago, but what are you trying to
do? Drive some LEDs from a single battery i gather? I've been meaning to do
that to make a flashlight, actually.

How many LEDs do you need to drive, and at what current level?

Have you seen some of the DIY flashlight circuits available at Dealextreme?
http://www.dealextreme.com/details.dx/sku.25505

<http://www.dealextreme.com/details.dx/sku.25505>For circuit design, I use
the calculator on http://www.national.com/analog but it is focused on Lumen
output. Helpful though. You can also just look at their LED drivers section.
I found this chip with a quick search. Needs at least 3V but might be
helpful. Simple enough to use too.
http://www.national.com/pf/LM/LM3405.html#Overview

I've become pretty familiar with their drivers, and could pretty easily lay
out a board to help if you need it. Then you could get them made at
BatchPCB, and if you need help assembling, I may be able to help at my place
in the South Bay. I am normally really busy, but this actually wouldn't take
too much time, and I've been interested in doing more open source LED
boards. I actually recently registered OpenSourceLighting.com, though I
haven't done anything with it yet. I want to combine 3D printing from Ponoko
with boards from BatchPCB, and create a little community to help people with
designing LED lighting solutions. Don't know if I'll ever take it off
though.

-Taylor Alexander




On Thu, Jan 6, 2011 at 12:17 PM, meredith scheff <satiredun at gmail.com>
wrote:
> Thanks everyone!
> It's the booster that I was thinking of, i'm looking forward to trying it.
> It's a big hurdle in wearable electronics.
> M
>
> On Thu, Jan 6, 2011 at 5:11 AM, Christoph Maier
> <cm.hardware.software.elsewhere at gmail.com> wrote:
>>
>> On Wed, 2011-01-05 at 21:30 -0800, T wrote:
>> > > Now, what's all this SEPIC stuff, anyways?
>> >
>> > SEPIC is a particular type DC-DC converter such as buck, boost,
>> > buck-boost, can cuk
>> >
>> > http://en.wikipedia.org/wiki/SEPIC
>>
>> SEPIC is what Dr. Foote calls a boost converter
>> http://en.wikipedia.org/wiki/Boost_converter
>> in last November's Five Minutes of Fame,
>> http://www.ustream.tv/recorded/10946425 ,
>> beginning at about 49 1/2 minutes.
>> (Can anyone, by any chance, post the slides somewhere,
>> Nudge nudge. Nudge nudge. Know what I mean?)
>>
>> Unlike the two-component solution
>> [ http://www.diodes.com/datasheets/ZXSC380.pdf
>> page 1, "Typical application circuit",
>> and page 6, "Application Notes", Fig. 2],
>> with a current regulation and efficiency that is so-so
>> [see the graphs on page 3],
>>
>> Jonathan draws some serious power,
>> so he needs a little more than 2 components,
>> probably even more than the 5 components in Fig. 5,
>> to control current and efficiency more accurately
>> than the ZXSC380, which is more optimized for blinkenlights
>> (well, ok, 200kHz blinkenlights,
>> so it looks continuous to the human eye)
>> running off a single 1.5V-ish battery.
>>
>> An LT3092 is the [Norton] equivalent of a waffle iron,
>> as presented in
>> http://www.ustream.tv/recorded/10946425 , 51:40 minutes.
>>
>> [ http://en.wikipedia.org/wiki/Emperor_Norton ,
>>  http://en.wikipedia.org/wiki/Norton_equivalent ]
>>
>>
>> HTH
>> Christoph
>> --
>> Linear current sources are easy,
>> [
>>
http://reference.kfupm.edu.sa/content/c/m/cmos_current_reference_without_resistanc_122569.pdf
>> ,
>>  http://www.eelab.usyd.edu.au/andre/publications/BiasgenAICSP.pdf ]
>>
>> getting sufficient control over the necessary means of production,
>> however ephemeral, is anything but.
>>
>>
>> _______________________________________________
>> Noisebridge-discuss mailing list
>> Noisebridge-discuss at lists.noisebridge.net
>> https://www.noisebridge.net/mailman/listinfo/noisebridge-discuss
>
>
>
> --
>
> Ladycartoonist.com
>
> ___________
>
> A human being should be able to change a diaper, plan an invasion, butcher
a
> hog, conn a ship, design a building, write a sonnet, balance accounts,
build
> a wall, set a bone, comfort the dying, take orders, give orders,
cooperate,
> act alone, solve equations, analyze a new problem, pitch manure, program a
> computer, cook a tasty meal, fight efficiently, die gallantly.
> Specialization is for insects.
>
> -Robert A. Heinlein
>
> _______________________________________________
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> Noisebridge-discuss at lists.noisebridge.net
> https://www.noisebridge.net/mailman/listinfo/noisebridge-discuss
>
>
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