Archive for category video

Energy Harvesting – battery-free radio

We’re working on some energy harvesting projects – and we learned about this amazing project – a radio powered only by the sound of the voice of the person talking at the transmit end.

El Silbo, voice powered radio design by MJ Rainey

This was able to transmit 150 miles with NO batteries at all. And no ‘super caps’ either. Just the transient power of his voice. Michael Rainey provides a schematic here:  Schematic of voice powered transmitter, El Silbo.

The trick for using a speaker as a microphone to absorb sound wave power is to get a good step-up transformer. The speaker has current, but little voltage, even into a high impedance. Of course, you can get more power output using the tin can approach, demonstrated in this video:

AA1TJ voice powered TX transatlantic attempt. No batteries.

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The mirror puzzle

Somehow, a mirror ‘knows’ to swap left and right, but not up and down.

Ok, stand in front of the mirror and it swaps left and right – you wiggle your right hand, the left hand wiggles in the mirror. But, up and down don’t get swapped, the top of your head is still at the top. More puzzling – when you lie down, the mirror still ‘knows’ when you right hand moves, and ‘shows you’ a left hand moving. Asking a few good questions leads to the real answer. Here’s another Feynman video. Enjoy.

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Feynman explains how trains stay on track

In this short video, physicist Richard Feynman describes the fun of figuring out how things really work. The example he uses here is how trains stay on their rails.

No, it’s not those flanges (though that seems obvious at first). In a way it’s a kind of ‘closed loop servo system’ or a self-correcting mechanism. In mechanical design I’ve heard this idea called ‘self-help’ where loads get distributed evenly by a careful design (see the book The Elements of Mechanical Design by James Skakoon for more on this topic).

This shows a microcosm of the job we do working with clients, solving problems – we always care about how things really work, and this video shows an example where the first ‘obvious’ idea may not be quite right.

In any case, it’s always fun to hear Feynman explain stuff. There’s a load of footage of him at youtube, explaining fire, light, uncertainty. Enjoy.

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