simplest offline circuit to power a small LED for a short time

On a sunny day (Mon, 01 May 2017 22:52:10 -0400) it happened snipped-for-privacy@notreal.com wrote in :

OK other solution: Big flywheel, generator, LED.

On a sunny day (Tue, 2 May 2017 01:30:13 -0700) it happened Jamie M wrote in :

So true.

On a sunny day (Tue, 2 May 2017 01:34:25 -0700 (PDT)) it happened snipped-for-privacy@gmail.com wrote in :

I dunno, never used those, only use Microchip 18F14k22 in all projects, never reached memory, speed, or power limit.

>

This is an interesting problem. What color LED are you planning on using ? Supposing that it is a white light LED, with a nominal voltage of 3.0 V and nominal current of 35.0 mA, the power requirement for 1 LED is 1.05 Watts, so that at 2 Watts, there is just about enough power for 2 of these. What battery are you planning on using -- both a 4.2 V or 3.7 V battery should work fine, and with an Ampere-Hour rating of e.g.,

1800 mAh or 1.8 Ah, it sould work just fine. No need for any ultracapacitor or microcontroller etc.,

big issue.

--sp

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Best regards,  
Spehro Pefhany

OK, which is worse?

It's possible to start a car at -40 but it had better be in perfect running condition. You're not going to get many chances. ;-)

How about a tritium light?

y becomes a

That's why crank starting handles persisted for so long for such regions. I t wasn't until the 80s that Russia dropped them in Siberian spec cars.

NT

On a sunny day (Tue, 02 May 2017 21:28:10 -0400) it happened snipped-for-privacy@notreal.com wrote in :

He wants a 2W LED, if that is anything like my Cree flashlight.. I *have* a tritium light, you can see it in the dark only, and... requirement was that it fades out IIRC.

Yeah, I missed the 2W part. If that's the requirement, batteries are the only way to go. A supercap isn't going to hack it. BTW, tritium lights will fade out. ;-)

There's no reason to disqualify the phosphor on scale (just paint a big enough surface area).

On a sunny day (Wed, 03 May 2017 12:55:12 -0400) it happened snipped-for-privacy@notreal.com wrote in :

I know, been measuring that since 2012: