[Sprite_TM] was tapped to build a rather large quiz buzzer system. Judging from his past work we’re not surprised that he seemed to have no trouble fulfilling the request. As the system is not likely to be used again (or rarely if it is) he found a way to finish the project that was both quick and inexpensive.
Each buzzer consists of a base, a button (both mechanical and electrical), and a couple of LEDs to indicate who buzzed in first. The mechanical part of the button uses a plastic bowl from Ikea and a wooden dowel surrounded by some pipe insulation. A momentary push switch is glued on the top of that dowel, and the insulation projects above that just a bit. This way it acts as a spring. The Dowel has been sized so that the bowl lip will hit the wooden base just as it clicks the switch.
As you can see, all of the buzzers are interlinked using Ethernet cable. The real trick here is how to read 14 buttons using just one CAT5 cable. This is done with the clever use of a 4×4 button matrix for a total of 16 buttons. The matrix also includes the LEDs for each buzzer. Since CAT5 has four twisted pairs this works out perfectly.
Looking for a more robust system thank this? Here’s a pretty nice one.