Roman Black wrote:

> A decent sized DC motor, say 3" x 5" will
> spin that up. Direct drive, no need for gears.
> If you get a 24v servomotor from a scrapyard
> it should even have an encoder attached for
> speed control, or data sync.

I disagree. A DC motor has very little efficiency as a relatively low RPM.
Even 300-400 rpm, the current speed, is a very low speed for a normal 3-pole
DC motor. max efficiency lies at 10 to 20 times as high an rpm. The blue
motor I described actually IS a servo with its 4 brushes, 16 poles and a 480
slot encoder and index slot. It draws 2 amps at 15 volts, and it hardly
spins; it runs pretty hot. The motor I added later on (with the gears) draws
3 amps at 3 volts and gets the whole thing moving, without getting warmer.

> I think it is more innovative without the
> disc. It is transparent so the light seems to
> some from thin air. JMHO :o)
> -Roman

And a lot easier to transport!

Robert Rolf wrote:

> The down side to a disk is not so much the weight as it is the turbulent
surface
> area that gets created. You'll need a more powerful motor for a given RPM.

On the contrary, I believe. A flat surfaced disk, for instance made of
plexiglass, has almost no air resistance. My rectangular arm spun almost
twice as fast after I added the paper "wings". Even now it pulses the air as
the arm passes.

> Have you also thought about putting you LEDs on the back side of the beam
> so that the image is visible from BOTH sides?

Not really. The way I use the display, clamped into a light grid or onto a
balcony, viewed from below, it wouldn't be useful.

> Have you thought about stacking clear LEDs so that you can create the
illusion
> of depth?

As a matter of fact I did, but I think the result won't add much to the
already spectacular sight of the display itself. And even if you use clear
leds, the bottom layer will look blurred from certain viewing angles. I'd be
more tempted to try dual color leds.

> Have you tried a bit of thick grease on the gear mesh? The really viscous
stuff
> does wonders (100wt).

The gear mesh is lubricated with car motor oil (it's all I got), but the
problem really is the larger gear. It's just a cheap nylon one, and it's a
little bit a-centric and raspy. The motor's metal gear is nicely made.


_______________

I don't think I'll be working on the display some time soon, as it's in full
working condition right now, and I have more projects on-stack right now
(16x16 audio switch matrix w/ AD75019 chip) But having written the software,
it shouldn't be too hard to make a new one without all the downsides the
current display has. Improvements could/would be for instance:
- Dual color leds from edge to center
- disk carrier
- 220 VAC fan motor (3000 rpm)
- serial interface (current loop or IR) to edit scroll text, set time/date,
upload logos/software etc.

Talk to you later,

Joris.

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