[Noisebridge-discuss] Two-way optical interface?

[Casey Callendrello]

What about some sort of magnetic sensor? Paint one pole white, the other
black, and make a grid of 361 bipolar reed switches or hall effect sensors?

I couldn't find a non-latching bipolar hall-effect sensor, but others
might have more luck.

--Casey

On 8/24/12 4:03 PM, Ari Lacenski wrote:
>
>     Could any of y'all help me with that? I have no experience at all with
>     photodiodes; I mainly do web apps, not hardware, so I don't even know
>     where to begin there.
>
>  
> I'd be up for laying out my understanding of a plan of attack; other
> people who've looked at analog components more recently could make
> better recommendations on part numbers. Let me know off-thread if you
> want to collaborate on that, I guess? It seems too much for one email.
>  
>
>     Also, any thought as to whether it'd be possible to run this through a
>     single Thingy? I'm picturing eg little plastic stubs touching the
>     actual board surface; those stubs underneath are connected to fiber
>     optic, which has a splitter - one end taking input from individual
>     LEDs, the other end going to a photodiode array for reading. But I
>     have no idea if this kind of simultaneous i/o split is even possible.
>
>
> The approach I have in mind involves multiplexing sensors that are all
> being polled by a single Thingy. I've made 12 inputs at a time work.
> Not 19^2, but they needn't all be on the same processor.
>
> <jazzhands>
> There's another possibility in gaining an image of a whole board at a
> time, using a wide-angle lens not a fiber-optic setup, and doing some
> edge detection.. uh.. stuff . This is how the homebrewed multitouch
> table at C-Base works, except it's using IR spectrum instead of
> visible. I know basically nothing about camera image processing! Yay.
> </jazzhands> 
>  
> >> Or you could hack up a two-color monome with the buttons at crosses.
>
> >That looks pretty neat equipment. Though expensive and sold out, and
> not available in 19x19. ;-)
>
> Sparkfun sells https://www.sparkfun.com/products/7835, which is
> readily chainable, 97% as nice, and 100% as much fun to poke.
>
> Ari 
>
>     > Daylight might ruin this whole plan; choosing a photodiode
>     responsive to
>     > only a certain spectrum would help. I recommend NOT choosing the
>     IR spectrum
>     > to play with.
>
>     *nod* Ideally I'd like it to work in a reasonably wide range of
>     lighting conditions; the display part might need to be pretty bright
>     to be seen though, especially when diffused as a halo.
>
>     On the up side, if the stone is covering the Thingy/photodiode, then
>     that blocks most outside light. Worst case scenario, it shouldn't be
>     too hard to distinguish 'stone' from 'no stone'. I don't know if my
>     "shoot light at it and read the reflectance through the same Thingy"
>     idea is viable, but at least the presence of the stone creates a
>     relatively controlled situation.
>
>     Though hm, it wouldn't necessarily be *directly* covering the Thingy
>     ('cause go stones have a relatively small contact surface, and move
>     around a bit).
>
>     This is also potentially a method for playing chess or the like, with
>     the same board. You'd need to cover the pieces' bases with something,
>     but then you get to control what that something is for optimal
>     distinctiveness.
>
>     > It might not work at all, but little cones of light spilling
>     from the edges
>     > of stones sounds like a lovely game.
>
>     *nod* I imagine one could make all sorts of neat variants if this
>     works. First getting it to work, though...
>
>     > Or you could hack up a two-color monome with the buttons at crosses.
>
>     That looks pretty neat equipment. Though expensive and sold out, and
>     not available in 19x19. ;-)
>
>     - Sai
>
>
>
>
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