Astable 555 timer - 8-bit computer clock - part 1

The best first breadboard build here for anyone who wants to understand what they are wiring, not just copy it. Ben Eater sets up a 555 timer as an astable oscillator, a circuit that pulses on and off by itself, and works out how the resistors and capacitor set the charge and discharge times, and with them the rhythm and the duty cycle. It opens the clock module of his 8-bit breadboard computer, but it stands perfectly well alone and needs no code. At about 28 minutes it is slow and careful, which is exactly right when you are checking every wire against his.