The Band’s Name In Lights, RGB LEDs To Be Exact.

A few of [michu]’s friends formed a band named Kalikut Now and needed an awesome stage show. The band made a few 80cm-high letters of their band name, cut a few pieces of acrylic, and wired them up with a few LED modules. The work of connecting these letters to a computer and programming them fell on [michu], and we’ve got to say he did a pretty good job.

You may remember [michu] from his StripInvaders and PixelInvaders projects, basically a few RGB LED modules that can communicate with an Arduino over an SPI interface. With these huge letters, [michu] ran into a problem: he had 11 meters of cabling between the clock and data lines, far beyond the maximum recommended length for any datasheet.

[michu] looked around the Internet for common problems with SPI interfaces and found a lot of good advice from a lot of very smart people. The issue with the SPI bus was eventually solved by correctly wiring the grounds of his LED modules, building a few dead-simple SPI buffers, and reducing the clock speed of the SPI bus.

After countless hours, the band’s name is in lights, and RGB LEDs to boot. Everything can be controlled with Abelton Live, and looks absolutely fantastic as seen in the video after the break.

18 thoughts on “The Band’s Name In Lights, RGB LEDs To Be Exact.

  1. In his ground routing example. The first image shows the ground being daisy chained. In the second he shows a loop. Wouldn’t his “correct” solution have the potential to create a noisy ground loop? Wouldn’t a better solution would be to create a seperate ground line and each module attach to that ground on its own. A sort of ladder if you will.

  2. “looks absolutely fantastic as seen in the video after the break.”

    Blank black area.

    When will people realize that Vimeo plain doesn’t work and stop trying to be “too cool for YouTube”?

    At least YouTube works.

    1. I click on the black and a player and start picture emerges, it does not play but I click on the word ‘vimeo’ in the corner and a new tab opens with the video on where it does play fine.

  3. A stage can be an incredibly (electrically) noisy environment. Most of the clubs I played in (many years ago) had bad power or noisy dimmer packs for stage lighting. We even did outdoor events where the stage was a flatbed semi…and power came from generators.

    Because of that, I’d never use a voltage-level protocol to communicate in that kind of environment– and that’s not even accounting for the difficulty in maintaining common grounds, or the susceptibility of a high impedance logic input to being zapped by a static charge when the equipment is being handled and set up.

    Instead, look at the way the physical interface for midi is constructed— an optoisolated current loop. Keep your SPI if you’d like, but add the midi front-end electronics.

    This will give you high noise immunity, robust protection against static, a decent data rate, and no worry about maintaining ground levels from device to device.

      1. Agreed on using RS-485. I’ve used it on a number of scalable LED lighting projects and while wiring can be a pain, it’s quite worth it. Plus, Cat 5 cable is basically free so it’s easy to route differential pairs.

        Just make sure you terminate your RS-485 lines. :)

    1. Agree – RS485 is the industrial standard in various forms for anything that has to talk over some distance in noisy environments. CCTV links, stage lighting (DMX), factory control systems, alarm systems.

      Then again, if I had a penny for every HaD project that reinvents the wheel, but squarer and held together with duck-tape, I’d have enough pennies for a few MAX485s ;)

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