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<div class="moz-cite-prefix">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?<br>
<br>
I couldn't find a non-latching bipolar hall-effect sensor, but
others might have more luck.<br>
<br>
--Casey<br>
<br>
On 8/24/12 4:03 PM, Ari Lacenski wrote:<br>
</div>
<blockquote
cite="mid:CA+=Z=27C8j1L6aRtcxYpsfx98bf-6J+vyGsbDhVyoUzKFyVePw@mail.gmail.com"
type="cite">
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im">Could any of y'all help me with that? I have
no experience at all with</div>
photodiodes; I mainly do web apps, not hardware, so I don't
even know<br>
where to begin there.<br>
</blockquote>
<div> </div>
<div>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.</div>
<div> </div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
Also, any thought as to whether it'd be possible to run this
through a<br>
single Thingy? I'm picturing eg little plastic stubs touching
the<br>
actual board surface; those stubs underneath are connected to
fiber<br>
optic, which has a splitter - one end taking input from
individual<br>
LEDs, the other end going to a photodiode array for reading.
But I<br>
have no idea if this kind of simultaneous i/o split is even
possible.</blockquote>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div><jazzhands></div>
<div>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.</div>
<div></jazzhands> </div>
<div> </div>
<div>
<div class="im">>> Or you could hack up a two-color
monome with the buttons at crosses.<br>
<br>
</div>
>That looks pretty neat equipment. Though expensive and
sold out, and<br>
not available in 19x19. ;-)</div>
<div><br>
</div>
<div>Sparkfun sells <a moz-do-not-send="true"
href="https://www.sparkfun.com/products/7835">https://www.sparkfun.com/products/7835</a>,
which is readily chainable, 97% as nice, and 100% as much fun
to poke.</div>
<div><br>
</div>
<div>Ari </div>
<div><br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im">
> Daylight might ruin this whole plan; choosing a
photodiode responsive to<br>
> only a certain spectrum would help. I recommend NOT
choosing the IR spectrum<br>
> to play with.<br>
<br>
</div>
*nod* Ideally I'd like it to work in a reasonably wide range
of<br>
lighting conditions; the display part might need to be pretty
bright<br>
to be seen though, especially when diffused as a halo.<br>
<br>
On the up side, if the stone is covering the
Thingy/photodiode, then<br>
that blocks most outside light. Worst case scenario, it
shouldn't be<br>
too hard to distinguish 'stone' from 'no stone'. I don't know
if my<br>
"shoot light at it and read the reflectance through the same
Thingy"<br>
idea is viable, but at least the presence of the stone creates
a<br>
relatively controlled situation.<br>
<br>
Though hm, it wouldn't necessarily be *directly* covering the
Thingy<br>
('cause go stones have a relatively small contact surface, and
move<br>
around a bit).<br>
<br>
This is also potentially a method for playing chess or the
like, with<br>
the same board. You'd need to cover the pieces' bases with
something,<br>
but then you get to control what that something is for optimal<br>
distinctiveness.<br>
<div class="im"><br>
> It might not work at all, but little cones of light
spilling from the edges<br>
> of stones sounds like a lovely game.<br>
<br>
</div>
*nod* I imagine one could make all sorts of neat variants if
this<br>
works. First getting it to work, though...<br>
<div class="im"><br>
> Or you could hack up a two-color monome with the
buttons at crosses.<br>
<br>
</div>
That looks pretty neat equipment. Though expensive and sold
out, and<br>
not available in 19x19. ;-)<br>
<span class="HOEnZb"><font color="#888888"><br>
- Sai<br>
</font></span></blockquote>
</div>
<br>
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