[Noisebridge-discuss] driving multiple LEDs with minimal batteries

jim jim at systemateka.com
Thu Jan 6 15:31:03 PST 2011


hey, taylor! i hope you show up at the NB space 
and toy around with the various electronic tools 
and supplies that are here. 



On Thu, 2011-01-06 at 13:00 -0800, Taylor Alexander wrote:
> 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
> 
> 
> 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
> >
> > _______________________________________________
> > Noisebridge-discuss mailing list
> > Noisebridge-discuss at lists.noisebridge.net
> > https://www.noisebridge.net/mailman/listinfo/noisebridge-discuss
> >
> >
> 
> 
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