[Noisebridge-discuss] LED scarf with*out* batteries [driving multiple LEDs with minimal batteries]

Taylor Alexander tlalexander at gmail.com
Mon Jan 17 12:41:38 PST 2011


It really sounded like the OP wanted to "build", not "learn", so
something pre-made is probably best.

I mentioned before, you can get extremely cheap booster circuits
designed for DIY-flashlight people, for ~$2 from dealextreme.

Here is one: http://www.dealextreme.com/details.dx/sku.25505
Specs are a little unclear, but comments say
3.2v 650ma output, and that it works with a single battery input.

They're designed for flashlights, so the pads are a little funny, but
overall they look like just what the OP wants.



On Mon, Jan 17, 2011 at 11:14 AM, T <t at of.net> wrote:
> ...
>>> The OP was looking for a simple way to add lights to a scarf, IIRC,
>>> and didn't have much electronics experience and some trepidation at
>>> building anything complex.  I fear we have driven her away.  Or
>>> perhaps I misjudge...
>>
>> Which solution did you end up going with, Meredith?
>
> Yes, tell us.
>
>> Power supplies being what they are, it occurs to me that it would be a
>> good idea to have a poster near the components showing the fundamental
>> linear power supply types and the simpler switching ones.  I'll draw
>> one up.  ...
>
> Thank you for that.
>
>> It would also be nice to put the typical conversion efficiencies next
>> to each power supply type to help the reader select an appropriate
>> circuit, but a quick look through my handbooks doesn't give me any
>> useful data.
>
> Hmmm.  I recall an online DC-DC switch-mode design thing where you
> could get efficiencies calculated... IIRC the values of the inductors
> and capacitors and the switching frequency made a big difference.
>
> Hey, just found this.  Looks like you can power a circuit from a
> thermal gradient!
>
> On the kind of night where you'd need a scarf you could have the
> required 5 degree C (K) gradient between your body and the air...
>
> Part 1:
>
> http://new.eetimes.com/design/power-management-design/4211949/Ultralow-voltage-energy-harvester-powers-wireless-sensors-from-waste-heat--Part-1-of-2-?Ecosystem=power-management-design
>
> Part 2:
>
> http://new.eetimes.com/design/power-management-design/4211950/Ultralow-voltage-energy-harvester-powers-wireless-sensors-from-waste-heat--Part-2-of-2-?Ecosystem=power-management-design
>
> Best Regards.
> T
>
>
> Best Regards.
> This is unedited.
> P-)
>
>
>
> ...
>>> The OP was looking for a simple way to add lights to a scarf, IIRC,
>>> and didn't have much electronics experience and some trepidation at
>>> building anything complex.  I fear we have driven her away.  Or
>>> perhaps I misjudge...
>>
>> Which solution did you end up going with, Meredith?
>>
>> Power supplies being what they are, it occurs to me that it would be a
>> good idea to have a poster near the components showing the fundamental
>> linear power supply types and the simpler switching ones.  I'll draw
>> one up.  If anyone has spare switching ICs they'd like to donate, let
>> me know before Friday and I'll add them to the poster.
>>
>> It would also be nice to put the typical conversion efficiencies next
>> to each power supply type to help the reader select an appropriate
>> circuit, but a quick look through my handbooks doesn't give me any
>> useful data.  Is there a good reference that takes into account modern
>> battery chemistries?
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