On Thu, Feb 23, 2006 at 09:39:26AM -0700, Robert Rolf wrote:
> 
> Peter Todd wrote:
> > Anyone have any experience with this? I just started a project that will
> > be a cube with 6 led matrix displays, one on each side, using 5x7 led
> > modules. Each side will end up as a 35x35 matrix that will then display
> > a 3d rendered wireframe image of a cube. The part that makes it all
> > worth doing, is I'm incorporating a high-resolution 3-axis tilt sensor
> > into the center of all this, so while you can rotate the physical cube,
> > the virtual, rendered cube, will always remain stationary.
> 
> So when kids shake the cube, what happens? A typical tilt sensor is going to
> go crazy, as will the software. You need a combination of tilt and
> rotation sensors to keep the 'virtual cube' stationary in space.
> I would suggest testing your sensor filtering and display
> algorithms first or you may be quite disappointed with the final result.
> And if shaking the unit makes the display go berserk, you can bet that
> the kids will shake it vigorously.

Well to be exact I'm planning to use a 3-axis acellerometer,
http://www.sparkfun.com/commerce/product_info.php?products_id=252, as my
tilt sensor. So I know that it's only referencing to gravity, therefore
already it's ignoring any movement parallel to gravity, such as spin.

My guess is that any vigourous movement will cause a lot of weird stuff
to display from the non-gravity accellerations present. But the display
should get more stable as movement stops, because I'll always be
directly referencing gravity to decide what to display.

It's not a perfect situation, but I think for a first try it'll make for
a decent effect. I'm designing the system to be modular, so at the very
center will be a seperate circuit board that just does the tilt
processing and then tells the display boards exactly what I want
displayed. So when the first version doesn't work will enough, I'll swap
the tilt board out. I'm also planning to try to leave some physical
space in case I need to have an acellerometer some displacement from the
center of the unit, so as to better measure rotation from the
accellerations.

Come to think if it, I'll bet you kids would love seeing the display go
berserk after some vigorous shaking... haha, anyway, my intended
audience is really crusty art collectors who will probably not even look
at it and instead nod their heads at how brillient a concept it is... If
they ever buy it, it'll be kept in some box somewhere, never seen again.

> Given the effort you are putting into this, it might be worth looking
> at using tri color LEDs so that you have something even more colorful
> when you're done.

Quiet frankly, nah, I don't mean to ignore your suggestion, but I'm
lucky enough as it is to get my LEDs as cheap as I have, $0.60 each, and
that requiered a decent amount of research. Tri color will definetely
blow my budget unfortunately.

-- 
pete@petertodd.ca http://www.petertodd.ca
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