[Noisebridge-discuss] driving multiple LEDs with minimal batteries

Christoph Maier cm.hardware.software.elsewhere at gmail.com
Thu Jan 6 05:11:20 PST 2011

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
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 ]

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.

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