+1 for the soldering iron. There was nothing quite so stressful as the first time you plugged in the prototype relay controller you'd built on Veroboard out of

+1 for the soldering iron. There was nothing quite so stressful as the first time you plugged in the prototype relay controller you'd built on Veroboard out of salvaged parts and a couple of 74-series logic chips. The whole thing was connected directly to the CPU via the edge connector, and if you didn't have flyback diodes and enough decoupling then every time the relay switched, the computer would crash with a psychedelic random bitmap on the screen and you'd wonder if it would ever work again... Ah, the nostalgia!