When Mark was in the lab last Thursday, he brought in the circuit with four cables attached. This was his first test with more than one alphanumeric split-flap display—a set of four, which we need to be able to program to display different letters. This will eventually lead to the final wiring of six letters and the two cartridges of the 24-hour clock display. After getting them to level out and running a few tests, we invited up Communications Studies’ own Douglas Hollingworth to see our run of four spell out his name. Here’s the wiring in action:
On our next test Mark moved on to try out his own name, but instead it flipped up as MORK. We guessed that this was because of the same dirty wheel conundrum we had with the new solo unit last week. We cleaned it off again with a little rubbing alcohol, reconnected it, and this time, it flipped perfectly to MARK. Seems like we’re going to need to clean the wheels on all of the units to make sure the display registers correctly. (On a side note, is it just me or are these all-caps 4-letter names somewhat reminiscent of the demons of Twin Peaks?)
Confident now that the board configuration will work for the Solari controller, Mark is now getting a PCB—a printed circuit board—made up. You’ll recall that Mark has been working from a large-size breadboard:
A breadboard makes it possible to plug in wires, capacitors, sensors, resistors, power sources, integrated circuits, diodes, and transistors and still move them around. It’s a temporary support consisting of a plastic board with rows of holes, and a metal backplate. The electrical parts are pushed through the board until they connect and hold with the metal plate. It’s a provisional circuit that can be tested, adapted, and moved around until you’ve got something you’re happy with. When I asked Mark about those two teal-headed pins in the center of the board, he told me that they’re used as placeholders. Sometimes you want to move a wire and try it somewhere else, but you don’t want to forget where it came from in case it doesn’t work and you need to move it back. The pin stands in and holds the place of the moved wire until you can confirm that the circuit will work in its new configuration.
Historically, breadboards were actually that—boards for bread. Electricians needed a way to affix and keep steady a circuit involving tubes, lights, transformers, and other large components. They would screw these components and wires into the board, and would be able to unscrew them and move them around as needed during the testing process. Check out a picture and more information here.
However, once the circuit is complete and ready to be used, the breadboard makes it very difficult to practically use. Though temporarily secure, wires can get fall out, the long metal arms of capacitors and resistors can lead to crossed wires, and the whole shebang can get tangled and messy. So, once your circuit is fixed, you can print a PCB, a circuit board which has all of those components, just laid out flat on a piece of non-conductive material. Wires are printed as copper lines, and other parts are soldered onto the board.
Our PCB will have our names silkscreened on it—Spikenzie Labs as the designer, and Flight YMX – Montreal Signs Project as the initiator. Like the small yellowing tag, written in Italian, that points towards the boards’ origin in Udine, this PCB will be our trace in the board, the index towards this project—this time and place.