[Noisebridge-discuss] driving multiple LEDs with minimal batteries

jim jim at well.com
Wed Jan 5 04:36:09 UTC 2011

   the best battery i could find on short notice 
seems to be the CR2450, size and weight about 
like a quarter ($0.25), a pretty good match for 
small fabrics. it presents 3 VDC at up to 30 mA 
constant current, enough to drive a few LEDs at 
reasonable brightness. 
   keeping in mind he possible requirement of 
minimal size and weight so's to be incorporated 
in a scarf or other small garment, what other 
battery is suitable? 

On Tue, 2011-01-04 at 20:21 -0800, Christoph Maier wrote:
> On Tue, Jan 4, 2011 at 12:06 PM, 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
> >
> > --
> >
> > Ladycartoonist.com
> I''m sitting here in the lab of a fellow (of the IEEE),
> [ http://pony.noisebridge.net/~cmaier/wearables/lab_with_stuff.jpg ]
> trying to make contributions to biomedical instrumentation,
> but I'm always running up against the problem of making circuits
> actually comfortably wearable.
> We usually end up using little PCBs (< quarter sized) and copper wires
> or ribbon cables.
> I've heard tell of some folks who make costumes that blink with sound,
> or dresses that point north,
> but I have no clue about this tailoring stuff.
> Could someone match me up with a talented seamstress?
> [For all you Terry Pratchett fans: Not THAT kind of seamstress!]
> > ___________
> >
> > 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
> Add "design a full custom CMOS biosensor IC" to that list.
> The little square insect in the middle of the green PCB to the left in
> http://pony.noisebridge.net/~cmaier/wearables/hackerspace_meets_academia.jpg
> kept me busy enough over the last week that I missed 27C3
> (well, at least I didn't end up in an apartment JotWeDe in Berlin with
> Leif this end of year).
> For electronics that's actually wearable,
> I'm kind of looking for an excuse to try to build some reasonably
> standard circuit,
> e.g., one with an LTC4060 [ http://cds.linear.com/docs/Datasheet/4060f.pdf ]
> on some PCB material that is more comfortable to wear than a rigid PCB.
> This kind of stuff:
> http://ladycartoonist.com/2010/05/soft-circuit-kits-now-for-sale-2/
> looks promising,
> but I'd need to find a way to find out the design constraints
> (minimum trace width, pitch, etc.) and feed them into an EDA program
> (default choice at the moment is Altium, for what it's worth),
> and have someone either do the sewing or teach me how not to mutilate
> myself with a sewing machine and/or serger.
> Eventually, some of these DIY microchips:
> http://www.facebook.com/photo.php?pid=31969144&l=6b994e53e9&id=1369525119
> should end up in a wearable, dare I think washable, garment.
> But for starters, a wearable charger for one of these slivery things
> on the lab bench,
> or an antiseptic SEPIC
> [ http://www.diodes.com/datasheets/ZXSC380.pdf or some such ]
> seems a good project.
> Christoph,
> playing postdoc @UCSD
> looking for a valid excuse for one of my quarterly noisebridge visits.
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