[HH] Controlling lots of LEDs with a microcontroller

[Drew Van Zandt]

If it's spinning and you are moving, there will be gyroscopic effects that
may cause issues.

*
Drew Van Zandt
Artisan's Asylum Craft Lead, Electronics & Robotics
Cam # US2010035593 (M:Liam Hopkins R: Bastian Rotgeld)
Domain Coordinator, MA-003-D.  Masquerade aVST
*



On Sat, Jan 21, 2012 at 6:54 PM, Tom Metro <tmetro+hhacking at gmail.com>wrote:

> Drew Van Zandt wrote:
> > The flexible PCBs are insanely expensive in small quantities.
>
> That's if you farm it out, right?
>
> What if you etch it yourself? That should be practical if you can get by
> with a single sided board with SMD components. Can you get the flexible
> substrate for a reasonable price?
>
> If not, perhaps it can be hacked together using something like a thin
> sheet of polypropylene (often sold as temporary cutting boards) with
> some self-adhesive copper adhered to it.
>
> Then there is the approach of drawing the circuits using conductive
> paints. Instructables.com is full of projects for making flexible circuits.
>
> Now that I look at the picture of what David wants to make, I see the
> curve in question is actually a flat 2-D circle. Not what I expected. So
> there's really no need for a flexible circuit. A simple flat, rigid PCB
> will do.
>
> This is going to pose some challenges to the legibility of your text, as
> you are going to have varying dot density as you go from the inner to
> the outer circles.
>
> "That's roughly a 30" circumfrence." -that's a lot of LEDs!
>
>
> David Kramer wrote:
> > Since the background needs to be
> > white, I was thinking of using foamcore boards
> > http://en.wikipedia.org/wiki/Foamcore
> >
> > ...I should be able to just push the LEDs through...
>
> Do you want the unilluminated LEDs to be visible protruding from the
> mask? I had assumed the LEDs would be mounted from behind and visible
> through some sort of a window (smoked or mirrored).
>
>
> > ...and bend the leads out which should keep the LEDs relatively
> > straight.
>
> Rather than pushing the leads through the foamcore, another option would
> be to punch holes through it that are slightly smaller than the LED
> bodies (assuming you use traditional round body LEDs), such that when
> they are inserted they'll be flush with the outer surface.
>
> In theory, if you could get your math and assembly tolerances good
> enough, you could still use SMD LEDs mounted to a flexible circuit. But
> good luck getting 100+ LEDs to line up with 100+ hand punched holes. A
> little CNC help would be good.
>
> The simplest approach I can think of is to make the outer circle
> entirely from a single-sided PCB, with no traces on the side that the
> LEDs mount on (and thus you'd use through-hole LEDs), and paint the
> board white.
>
>
> > It's been decades since I made a PCB.  While that would certainly be the
> > neatest solution (though not the lightest), I'm definitely not up to
> > making a PCB with hundreds of trace lines all going to the same general
> > area.
>
> It's not trivial, but it may be much easier than you think. You wouldn't
> "hand tape" the board. You'd do the layout in software. You've then got
> 3 options to manufacturer it: 1. farm it out for professional
> production; 2. find someone with a CNC router to do it; 3. make it
> yourself by using one of many techniques, such as toner transfer from a
> laser print to the board.
>
> As for weight, use as thin substrate. Or hack something together like
> substitute plastiboard (similar to foamcore, but waterproof) with
> self-adhesive coper applied to it.
>
>
> > I feel if I go this route instead of the mechanical rotating ring
> > design, though, I'll end up with a much better product and more
> > experience in embedded software.
>
> Actually I think the best option is to ignore everything above, and
> combine the two designs: rotating electronic LED display.
>
> http://www.youtube.com/watch?v=ML6ZrWKTWPo
>
> It eliminates a whole pile of challenges mentioned above, like getting
> hundreds of LEDs wired up and evenly spaced, and the dot density
> problems I mentioned. Now you only have to deal with driving 8 or 10
> LEDs. And making them RGB becomes far more practical.
>
> You just need to figure out how to get them to spin at a few hundred RPM
> without being too heavy (use a stepper motor from an old floppy drive?),
> being a danger to yourself and those around you, how to synchronize your
> message with the rotation, and how to get power and/or signals onto the
> spinning mechanism.
>
>  -Tom
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