On 2018-04-11 07:30, Henry Baker wrote:
I seem to recall that someone at MIT had developed an LED display for bicycle spokes that was time-multiplexed in such a way as to provide a full circular bit-mapped display -- kinda like those WWII radar displays.
These last have been around for at least 10-15 years. I may be picking at nits, and I haven't looked at one closely, but I'd guess that it was positionally multiplexed (if you know what I mean), not time-multiplexed. Assuming my guess is correct, the area covered by an LED closer to the rim would be larger (blurrier?) than the LEDs closer to the hub. The value of an LED would be dependent on the position of the wheel, and independent of rotational speed, and robust against variations in speed. Of course, the image wouldn't be very persistent or clear until you got above 2 or 3 frames per second, so you'd need to be going fast enough for the wheels to be rotating at 3*60/<# of spokes with LEDs> RPM. If you can fit 256 LEDs on a spoke you'd have a 512x512 display, but probably much smaller is more realistic -- but even 32x32 is sufficient for scrolling text.
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