It’s been way too long since I actually built this to remember exactly what was done, but, the pictures pretty much speak for themselves. We bought some wood, cut it appropriately to make a box w/out a back. Then, cut holes as best we could with an auger type drill bit. That might have been a mistake, those things catch on knots pretty easily, but it turned out pretty well. (Thanks Robby!).

Before or after wiring all the sockets ( I can’t remember anymore), 24 relay boards were made ( one for each column).  The relays are sharp solid state relays.  This is pretty important, number one, solid state, not mechanical.  That lets you switch at much faster speeds so the display can update faster, and it also doesn’t make any noise, think about that for a second, 120 relays switching as fast as they can would be overwhelmingly annoying.  Each relay is controlled from one of the shift register ports from the circuit, and switches power to an individual light bulb.  Also important, I’m using 7.5 Watt bulbs, that’s ~ 7mA per bulb.  These relays are rated to about 60mA, if you were to put in a 75 Watt bulb, you would blow the relay, but really, you would also be pulling 75 Amps of current!!  9 kW!  So don’t be stupid, that will never work, and would really be pretty blinding even if it did.

Next up, wiring all the sockets, this took….forever.  Each socket has two wires connected to it, one goes to the relay, one goes to the mains, each relay is connected to a shift register and also to ground, and also to mains.  Totallling……5 wires per bulb.  I made a few shortcuts here and there, but in the end there’s around 500 wires that need to be cut, stripped, and soldered on both ends.  That’s over one thousand soldering points!  Thankfully, I had help…