Luci RocksSep 3, 2019
thinking about how many sensors you can make using just an infrared led/light sensor, and clever mechanical designs.
a microphone by attaching the LED to a drum skin.
a rotation sensor by the wheel progressively obscuring the LED as it rotates.
a bend sensor by putting the LED in a straw.
an orientation sensor by putting a metal marble in a cage and bouncing light off it.
a compass sensor by sticking the light on a compass needle.
Show threadLuci RocksSep 3, 2019
a limiting factor of course is response time. but apparently you can get light sensors fast enough for the nes light gun to work based on CRT timing. so who knows.
Show threadLuci Rocks

at 50ns response time, it turns out, you can get around 500x500 resolution by my calculations.

also, if you couple with an RGB led, you can turn on R, then G, then B , taking readings for each, and get a surface color reading!

only somewhat related: I wish I knew what I was doing better with electronics. i dismantled a cheapo printer and there are TONS of stepper motors, optical sensors, gears and things. cheap printer salvage would be a nice source of components.

Sep 6, 2019 at 2:03pmWeb
Show threadLuci RocksSep 10, 2019

so i have this list of sensors you can build using just leds, and photodiode pairs along with some clever mechanical designs. in fact, the original ball mice used 4 leds and 4 sensors to pull quadrature encodings of the 2 axes off the spokes of two tiny plastic wheels. a printer i disassembled did the same thing with a circular disk of transparent photofilm for sensing the speed of a roller.

is there a name for this class of photodiode based sensing configurations?

Show threadunspeakablehorror (Reinstated)Sep 10, 2019
@zensaiyuki I don't know but that sounds like an intriguing sensor category!
Show threadhefSep 10, 2019
@zensaiyuki What are you doing to get 500x500 resolution with an led and light sensor?
Show threadLuci RocksSep 10, 2019
@hef light pen/light gun.
if you have a CRT. you can figure out where a lightsensor is pointing by timing when the scanline activates the light sensor in the pen.
Show threadLuci RocksSep 10, 2019
@hef the caveat of course is this doesn’t work with LCDs because they don’t have a scanning beam. but rven if you do, you need a lot of timing precision.