Tetris on the ceiling: chapter 1

Oooooh!Mm is excited to be moving towers soon, to a new shiny office inside a new shiny tower… and in the new tower, for reasons too pedestrian to recount here, the boring standard office ceiling tiles are being replaced with clear acrylic ones. This, of course, is awesome. But in what particular way?

Over a few cocktails and glasses of champagne at Guildford’s entirely un-legendary and slightly creepy The-Shining-esque hotel-bar-blue-light-travelling-salesman-horror-venue ‘The Mandolay’, the Molecules put their heads together. ‘What’, slurred Paul ‘Aggie’ Davis, ‘about adding coloured lights above the tiles?’
What indeed! I feel a lab project coming on…

A little drunken 3 am googling session later, whilst contemplating how one might wire up and control 2000 ceiling tiles with coloured lights, I discovered this rather wonderful chip: the Allegro A6281.

Are all my dreams answered?

  • PWM brightness controller with constant current LED output stage? CHECK.
  • Serial input of data to reduce number of wires? CHECK.
  • Really simple to wire up because I’ve forgotten all my electronics? CHECK.
  • Easy to solder…. oh wait its surface mount only.

Never mind! It was late, I was drunk, details like circuit boards et al can be sourced later. Next: LEDs! Oh wait, no-body seems to want to supply LEDs to me in Europe, much less tell me which of the bewildering LED selection available on the whole of the internet’s six billion pages to order. Curses.
But then… America saved my ass. Specifically Macetech and their oh-my-god-it-was-made-for-me-surely-this-is-too-good-to-be-true, shiftbrite product.

Basically, shiftbrite is a cute little, 1 inch by 1inch, mini prefabricated circuit board with a little RGB LED and one of those Allegro chips all wired up and ready to go. On two of its edges are six pins, just like the ones you plug PC cpu fans into on your motherboard, to allow you to chain them together like fairy lights. Then you plug one end into a COMPUTER MACHINE, some JUICY FAT POWER, and it can control all the lights to be any colour you want. Witness 81 one of them gaffer taped to an ikea coffee table. so much win, we had to have them.

At this point, excitement was brewing. Ideas were flowing. If we could light all 2000 tiles of our ceiling under computer control, we’d essentially have a huge crazy RGB display on the ceiling… we could animate it in any way we wanted, we could run movies on it… we could play games on it… tetris or pong across the ceiling.  If someone broke the build, we could put a red light explosion above their desk. What else could we do?
An order for eight was made, and duly despatched. Maplin was raided for parallel port bits, my dodgy soldering iron was dug up, and this entirely safe monstrosity was created:
(Where Aggy found a pc with a working parallel port in 2010 is another story – but that’s what IT managers do, right? Find stuff that no-one else can find. It’s a kind of genius) The plan was, rather than using a fancy microcontroller as macetech advise, we’d plug eight chains of LEDs into the eight data pins of a linux based pc’s parallel port, and then use all the power of the pc to generate and play ‘awesome stuff’ over the internets.
A few lines of dodgy C later, we had the first 8 lights up and running:

Tune in next time, when I actually plug in for the first time, the first chain of 100 lights:
(despite epic temptation, unfortunately LBP work has prevented me from having time to try it. But oh, my blog reading friends, you’ll be the first to know when we switch on… well second I guess, we’ll know first!


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