I designed and built this simple "game show buzzer" device in 2007 for a college organization to use at special events. The device is an audio-visual annunciator system that is intended to be used by people during interactive group events such as game show competitions.
The device has six "call" channels, each which has a remote unit that consists of a large arcade-style push button switch. The switch is a spring-loaded momentary SPST switch that the user presses to register a "call". Each remote also contains four LED indicator lights; two amber lights to indicate the remote is ready "armed", and two blue lights to indicate when the remote has successfully completed a call.
The remotes connect to a central control unit via 4-conductor cables terminated with RJ-11 "modular" phone jacks. Since the cables use modular jacks, they can be easily extended using standard North American telephone cables and couplers (up to about 100 feet maximum length).
The central control unit consists of a power supply, power switch, 8-bit Atmel microcontroller, audible buzzer, and six standard (NEMA 5-15R) power output receptacles. Each receptacle is controlled via a SPST relay, and its operation corresponds to one of the six call channels. The buzzer is controlled by an additional relay and its operation corresponds to all of the six call channels.
When the device is turned on and in its idle state, the microcontroller continuously scans the six remote channels, waiting for a switch to be activated. During this time, the following conditions are true:
When a remote push button is pressed, its channel is activated for a duration of approximately 5 seconds, while the remaining channels are disabled (their input is ignored). During this time, the following conditions are true: