This post is on the design of the counter enclosure and the digits and individual LED segments.
I wanted the enclosure to have a “hacked together” look-and-feel, to fit the theme of the piece (accidents), and also because my woodworking skills aren’t that impressive. If it’s going to look crap, it may as well be intentional.
The basic way to get LED segments of this size seems to be using LED arrays behind some sort of diffusing material. After searching the hackspace for a bit, I found some sheets of fibreglass-like material that looked pretty much ideal, apart from being marked with a manufacturer’s stencil. I decided that this wouldn’t be noticed once mounted on a wall, and luckily I was right. The size of the sheets pretty much dictated the size of each digit.
Rather than cut out the segment shapes from foamboard or anything like that, I went down a much lazier route of laser-cutting the mask out of black card, which was glued behind the fibreglass:
Making the masks this way was really, really quick and created zero mess. (read Sparkfun’s adventures with styrofoam to compare). But with just those masks, the light from one segment would diffuse into another without a separator. These just ended up being bits of pine strip cut to length and stuck down in the box. And the box itself is pretty simple, just an MDF base and plywood sides:
Each segment uses three 5mm “Piranha” LEDs. If you’re interested, I’d recommend Phenoptix for all your LED needs. Especially if you live down the road from them and go to the same hackspace.
The LEDs are mounted on stripboard and have 240R of current limiting resistor per segment. Cutting up the stripboard and attaching mounting standoffs, and then the associated soldering was; if not most time-consuming; at least the most boring part of the project. I just hot-glue-gunned each LED strip into place in the box.
After all that, the result is a box full of LEDs and strips of pine, and some bits of fibreglass with card stuck to it. To attach the segments to the box and allow access for maintenance, I use a long hinge that (luckily) happened to be in a box of fixings. Together with some strips of aluminium and an old metal box I cut up, I managed to get a suitably horrible looking front for the box:
The one lesson to take away from all this is that the “black card and bits of wood” method is really good for a quick-and-dirty way to make massive LED segments. Replacing the wood with plastic or anything else suitable would work just as well.
More to come soon/later/in the far future. The next post will look at the electronics in the auto-dimming LED drive – designed to dim the LED segments when the ambient light level drops.