
No Battery – LED Flasher (2013) [video] - peter_d_sherman
https://www.youtube.com/watch?v=STPej7VQNzI
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lopmotr
That's just powered by a battery with dissimilar metals, isn't it? Kids do
this kind of thing in science class all the time making potato batteries.

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Tempest1981
Did anyone else use the LM3909 chip to build an LED flasher, back in the day?
It would blink once a second for 2+ years on a single D-cell battery.

[https://hackaday.com/2018/01/04/there-once-was-an-ic-
dedicat...](https://hackaday.com/2018/01/04/there-once-was-an-ic-dedicated-to-
blinking-an-led/)

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eps
OK, how does this work exactly?

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pi-rat
It's a battery-cell using ferrite (the rock) and aluminium foil as electrodes
and his hand as electrolyte. This produces ~0.7v which he then steps up using
something like a joule thief circuit[1].

[1]:
[https://en.wikipedia.org/wiki/Joule_thief](https://en.wikipedia.org/wiki/Joule_thief)

