michael brown wrote:

> 
> You two guys might be interested in this.  I was killing some time
> inside Spencer Gifts a couple of weeks ago while waiting on my wife to
> get out of the eye doctors office.  In the back of the store where all
> the black light stuff is, they had an interesting toy.  I guess you'd
> call it kinetic art, but it greatly resembles the propeller clock
> concept.  It's a black spinning disk about 12" or so in diameter.  It
> has 8 or 10 RGB LEDs arranged in a straight line from the center out to
> the edge.  As the disk spins, it creates interesting segmented
> multi-colored circular patterns.  I believe they were US$29.00 (maybe
> 39.00).
> 
> What really intrigued me was that every LED was individually
> addressable.  I wanted to buy it just to see how they did their slip
> ring coupling.  I wanted to see if they literally had the 30 odd
> individual contacts required to do the 10 or so RGB LEDs.  After
> thinking about it for a while with my "how cheaply could an engineer
> make this" mindset enabled, I figure that they just spin the entire
> electronics assembly and only transfer power (2 wires) thru the
> coupling, otherwise the coupling would probably be the most expensive
> part of the device.

I have one.
They just supply power to the setup with a single brush
and an copper tape on the plastic hub.
It uses a COB (chip on board, under epoxy) so there is no way to
access the device to reprogram it.

>  It makes nice patterns while still coming up to full speed, so I figure
> there is probably more than one disk position indicator.  I'm thinking a
> few magnets evenly spaced around the circumference of the disk and a
> single Hall sensor.  Or do you think they just use a single reference
> point and factor in the acceleration to keep the pattern nice and evenly
> layed out?

Just a mechanical contact that fires once per rev.
The acceleration is quite slow, but you can see the pattern
jump if you drop power for a moment since it assumes a certain
speed until it has completed one rev.


> After telling my wife all about it, she says I can have one to "tinker
> with".  ;-)  I wish to first see how it's constructed and then replace
> the "brains" of it with something a little more useful, like an
> analog/digital clock display that also does cute patterns that I like.
> ;-)

As noted above, you'll have to replace the COB with your own
device, but it's a simple LED matrix.

Have fun.

Robert

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