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 <[email protected]>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 > _______________________________________________ > Hardwarehacking mailing list > [email protected] > http://lists.blu.org/mailman/listinfo/hardwarehacking >
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