The idea is simple, the nozzle pushes down on the PCB which has a tact switch underneath. When the switch closes, an LED lights. In practice, you measure the height of the board and use that for ...

[bobricious] might have just cracked it. For his Hackaday Prize entry, he’s created a tiny USB keyboard out of tact switches. What’s the secret? An entire panel of PCBs. It looks great ...