[HH] Controlling lots of LEDs with a microcontroller

[Drew Van Zandt]

The flexible PCBs are insanely expensive in small quantities. If you're
doing this on a curve like the Daft Punk helmets, I'd suggest single-line
or dual-line PCBs with a vertically oriented row of LEDs plus a driver for
8 or 16 as applicable; SPI or I2C between.  Not good if you want to be able
to see through the LED matrix from behind, though.  Hand-soldering the LEDs
into an array is not so bad - use a wooden jig with a CAM-drilled hole
matrix to get the spacing perfect even in a hand-built array.  Red LEDs run
about a nickel each in quantity.

Some commonly available flexible RGB LED strips have LEDs roughly every
16mm, if that's close-packed enough for you, and they are cuttable into
groups of three.  Some trace-cutting and soldering is required to drive
them individually, though.  A 5-meter strip (300 LEDs) is about $30 shipped
from Hong Kong.

RGB takes 3X the I/O, however, for 360 LEDs worth.

*
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 2:59 AM, Tom Metro <tmetro+hhacking at gmail.com>wrote:

> Nuno Sucena Almeida wrote:
> > ...if you want to avoid too much soldering, consider using a led
> > matrix, instead of individual LEDs.
>
> That was my first thought as well. It'll give you a perfectly consistent
> LED spacing. But in addition to it not conforming to the curve, and that
> these types of matrix modules are a tad bulky, you would still have some
> soldering challenges. You'll still have a bunch of pins (12 for example)
> on each module and you'll have to mount it to perf board or sections of
> rigid PCB. You could, for example, put each display on its own PCB
> segment, and join the segments with some solid wire jumpers, which would
> act as a hinge.
>
> Another possibility is to use flexible LED strips, like these:
>
> http://www.google.com/products?as_q=flexible+led+strips&num=100&scoring=p&as_epq=&as_oq=&as_eq=&price1=&price2=&as_occt=any&show=dd&safe=active
>
> You'd presumably use as many strips as you want rows in your display.
>
> But they have two problems. One is that they typically don't have a
> dense enough spacing to make an effective display. The other is that
> they are typically wired in series, so you'd have to hack it by cutting
> traces and tacking on wires, which would be a mess.
>
> The ideal solution would be to create a custom display board using the
> same flexible PCB substrate used for the flexible strips. Incorporate
> the matrix driver onto the board. Use SMD LEDs and attach them with
> solder paste and baking in the oven, rather than individual soldering.
>
> Though not a quickie project.
>
> Also, consider using RGB LEDs so you can create even more effects.
>
>  -Tom
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