Magnets: Is There Anything They Can't Do?
Also this project began the use of wall power instead of battery power. This involved voiding the warranty on an AC adapter by exposing the wires so I could feed them in to my projects however I choose. A neat pro-tip from the book: When stripping the ends of an electrical cord like this, cut the two wires to different lengths. This prevents them from casually bumping each other and short circuiting if the cord gets loose. I always find this kind of handy folk knowledge to be fascinating, and one of my life ambitions is to contribute some small piece of tribal knowledge like this to the world, which will live on in usefulness for generations...
In keeping with it's "learn by discovery" manifesto, the book instructed me to extract the case from my relay so that I could figure out which pins were doing what and what has happening as it functioned. This part was fun, who doesn't like chopping things to bits, especially when you "know you shouldn't"?
It was a useful exercise, as the use of each pin is reasonably apparent just from visual inspection. (Provided I already knew how the thing worked.) Time to wire it up.
Alligator Clips Can DIE!!!
Actually I discovered a useful lesson: Every clip is a weak point that will flex and fall apart, and each additional wire is more weight and ungainliness, and the project became much more manageable when I used as few clips as possible and relied on the stiffness of the wires to hold things in place. The whole thing became more rigid and stable, and it was actually easier to hook things in place, even though I was fiddling with more ends per connection, and in tighter spaces.
In addition, I crimped a few of the alligator clips on to the ends of wires, so that I'd have one less bit to stuff in the jaws. This helped a lot, and I figure I'd actually probably have encountered very little frustration if I had just followed the book's advice and bought a handful of patch cables (short flexible wires with clips pre-attached to both ends).
Well, once it was all wired up, I grinned and pushed the button...
Noises! Physical noises! I was really not expecting that. Even though it is a magnet pulling a plate, it's a physical process, in my mind "electronic switch" somehow meant it was an electric-only process so the heavy clack of it switching surprised me quite a bit.
Better prepared, I pushed the button again, and watched as the lights flicked. I also really appreciated the advice to pull the relay apart, because it's a physical device and there's moving parts inside to see! Phooey on LEDs, I want to watch the little metal plates flipping around.
That was fun! But it's time to move on, apparently the next project has the relay switching itself...