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

T t at of.net
Mon Jan 17 11:14:16 PST 2011


...
>> 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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>


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