Scusate per la lingua Italiana.... non ho capito bene il principio di funzionamento di questo oggetto .... mi sembra di aver capito che , quando la velocità è quella giusta, i led si accendono nella stessa posizione di prima e la persistenza dell'immagine, sulla retina, fa il resto....è corretto?

No problem at all! Your understanding is quite close. Let me clarify just a little bit:

Each LED is mounted on the rotating disc and flashes at a fixed flash frequency. The key point is that the spacing between LEDs is wider than the angular distance the disc travels in one flash period. So while the disc moves through one LED-to-LED spacing, the LED flashes 3 or 4 times - each flash appears at a slightly different angular position to your eye. This is how the disc shows a continuous ring of dots: each physical LED produces 3-4 visible "light points" between its neighbors. Persistence of vision is what makes all those flashes appear simultaneously, but the dots you see at the in-between positions are real flashes of real LEDs - just caught at different moments as the disc rotates.

In principle, you could do the same with a traditional printed strobe disc by spacing the markings more sparsely, but the visible pattern would have lower contrast - the difference between marked and unmarked areas becomes harder to see. With LEDs, each flash is a sharp bright point against a dark background, so the contrast stays high enough even when the LEDs are spaced apart.

Thanks,

Very cool idea. 👍 Pity the technology didn't exist when I still had a turntable. BTW how about a {CR,LIR}2032 cell to reduce weight?

Thanks for your comment! Actually, the initial idea came from a strobe light module powered by a CR2032, but it turned out not to be suitable for this design, which needs to drive many LEDs.