If it's spinning and you are moving, there will be gyroscopic effects that may cause issues.<div><br clear="all"><span style="font-family:arial,sans-serif;font-size:13px"><b><b><div><span style="font-weight:normal"><b><b><span style="font-weight:normal"><span style="font-size:x-small">Drew Van Zandt</span></span></b></b></span></div>
<div><span style="font-weight:normal"><b><b><span style="font-weight:normal"><span style="font-size:x-small"><span style="font-family:arial">Artisan's Asylum Craft Lead, Electronics & Robotics</span><br>Cam # US2010035593 (</span></span></b></b><span style="font-weight:normal"><span style="font-size:x-small">M:</span></span><b><b><span style="font-weight:normal"><span style="font-size:x-small">Liam Hopkins </span></span></b></b><span style="font-weight:normal"><span style="font-size:x-small">R:</span></span><b><b><span style="font-weight:normal"><span style="font-size:x-small"> Bastian Rotgeld)<br>
</span></span></b></b></span><span style="font-family:arial,sans-serif;font-size:13px"><b><b><span style="font-weight:normal"><b><b><span style="font-weight:normal"><span style="font-size:x-small">Domain Coordinator, MA-003-D. Masquerade aVST </span></span></b></b></span></b></b></span><br>
</div></b></b></span><font size="1"><br></font><br>
<br><br><div class="gmail_quote">On Sat, Jan 21, 2012 at 6:54 PM, Tom Metro <span dir="ltr"><<a href="mailto:tmetro%2Bhhacking@gmail.com">tmetro+hhacking@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im">Drew Van Zandt wrote:<br>
> The flexible PCBs are insanely expensive in small quantities.<br>
<br>
</div>That's if you farm it out, right?<br>
<br>
What if you etch it yourself? That should be practical if you can get by<br>
with a single sided board with SMD components. Can you get the flexible<br>
substrate for a reasonable price?<br>
<br>
If not, perhaps it can be hacked together using something like a thin<br>
sheet of polypropylene (often sold as temporary cutting boards) with<br>
some self-adhesive copper adhered to it.<br>
<br>
Then there is the approach of drawing the circuits using conductive<br>
paints. Instructables.com is full of projects for making flexible circuits.<br>
<br>
Now that I look at the picture of what David wants to make, I see the<br>
curve in question is actually a flat 2-D circle. Not what I expected. So<br>
there's really no need for a flexible circuit. A simple flat, rigid PCB<br>
will do.<br>
<br>
This is going to pose some challenges to the legibility of your text, as<br>
you are going to have varying dot density as you go from the inner to<br>
the outer circles.<br>
<br>
"That's roughly a 30" circumfrence." -that's a lot of LEDs!<br>
<br>
<br>
David Kramer wrote:<br>
> Since the background needs to be<br>
> white, I was thinking of using foamcore boards<br>
> <a href="http://en.wikipedia.org/wiki/Foamcore" target="_blank">http://en.wikipedia.org/wiki/Foamcore</a><br>
><br>
> ...I should be able to just push the LEDs through...<br>
<br>
Do you want the unilluminated LEDs to be visible protruding from the<br>
mask? I had assumed the LEDs would be mounted from behind and visible<br>
through some sort of a window (smoked or mirrored).<br>
<br>
<br>
> ...and bend the leads out which should keep the LEDs relatively<br>
> straight.<br>
<br>
Rather than pushing the leads through the foamcore, another option would<br>
be to punch holes through it that are slightly smaller than the LED<br>
bodies (assuming you use traditional round body LEDs), such that when<br>
they are inserted they'll be flush with the outer surface.<br>
<br>
In theory, if you could get your math and assembly tolerances good<br>
enough, you could still use SMD LEDs mounted to a flexible circuit. But<br>
good luck getting 100+ LEDs to line up with 100+ hand punched holes. A<br>
little CNC help would be good.<br>
<br>
The simplest approach I can think of is to make the outer circle<br>
entirely from a single-sided PCB, with no traces on the side that the<br>
LEDs mount on (and thus you'd use through-hole LEDs), and paint the<br>
board white.<br>
<br>
<br>
> It's been decades since I made a PCB. While that would certainly be the<br>
> neatest solution (though not the lightest), I'm definitely not up to<br>
> making a PCB with hundreds of trace lines all going to the same general<br>
> area.<br>
<br>
It's not trivial, but it may be much easier than you think. You wouldn't<br>
"hand tape" the board. You'd do the layout in software. You've then got<br>
3 options to manufacturer it: 1. farm it out for professional<br>
production; 2. find someone with a CNC router to do it; 3. make it<br>
yourself by using one of many techniques, such as toner transfer from a<br>
laser print to the board.<br>
<br>
As for weight, use as thin substrate. Or hack something together like<br>
substitute plastiboard (similar to foamcore, but waterproof) with<br>
self-adhesive coper applied to it.<br>
<br>
<br>
> I feel if I go this route instead of the mechanical rotating ring<br>
> design, though, I'll end up with a much better product and more<br>
> experience in embedded software.<br>
<br>
Actually I think the best option is to ignore everything above, and<br>
combine the two designs: rotating electronic LED display.<br>
<br>
<a href="http://www.youtube.com/watch?v=ML6ZrWKTWPo" target="_blank">http://www.youtube.com/watch?v=ML6ZrWKTWPo</a><br>
<br>
It eliminates a whole pile of challenges mentioned above, like getting<br>
hundreds of LEDs wired up and evenly spaced, and the dot density<br>
problems I mentioned. Now you only have to deal with driving 8 or 10<br>
LEDs. And making them RGB becomes far more practical.<br>
<br>
You just need to figure out how to get them to spin at a few hundred RPM<br>
without being too heavy (use a stepper motor from an old floppy drive?),<br>
being a danger to yourself and those around you, how to synchronize your<br>
message with the rotation, and how to get power and/or signals onto the<br>
spinning mechanism.<br>
<div class="HOEnZb"><div class="h5"><br>
-Tom<br>
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</div></div></blockquote></div><br></div>