[Erik van Zijst] has had a long career as a programmer, but lacked an understanding of what was happening at a bare metal level. After building a few logic gates out of transistors to get a feel for electronics, he set out to build a working clock using 74-series logic. Naturally, it was quite the adventure.
The project starts out as many do on the breadboard. The requisite BCD counters and 7-segment displays were sourced, and everything was connected up with a cavalcade of colorful hookup wires. A 32.768 KHz crystal was pressed into service to generate the clock signal, divided down to get a 1Hz output to drive the seconds counter that would then run the entire clock. [Erik] then had to learn some more practical electronics skills, to deal with debouncing buttons for the time setting circuit.
With the clock now functional, [Erik] decided to take things further, aiming to build something more robust and usable. An automatic brightness control was created using a 555 to run a crude PWM dimmer for the LEDs. Additionally, a PCB was designed to replace the temporary breadboard setup. This led to problems with the oscillator that [Erik] couldn’t quite figure out. Rather than continue on the same path, he changed tack, instead replacing the quartz crystal with a modern MEMS oscillator that solved the problem.
It’s a great look at how to construct a working clock from bare logic, and one that serves to remind us just how complex even a seemingly simple device can be. We’ve seen other from-scratch builds before too, like this 777-transistor clock, or this attractive stacked design. Video after the break.