Reaction tester project from Vagrearg:
The single gate-type NAND version was put onto a PCB and tested. It works like a charm. There were only 74AC00 chips available at the time, but they are just about the same as HC chips. You can get the design files, which are made with KiCad. The layout is kept as symmetrical as possible and the A/B buttons are next to the LEDs. Power is supplied using three AA batteries in a standard battery-holder and the PCB is stuck onto the battery-holder with double-sided sticky tape.
Full details at Vagrearg project page.
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