Hand Sensors
The targets main purpose was to contain a hand sensor. To detect a hand, we built and calibrated our own infrared emitter/detector pair for hands at a range of 1-6 in. Due to the number of sensors, we determined the best means of control would be through multiplexers. Each player had four targets dedicated to him or her, and each target had three circuits muxed together into the microcontroller.
The target was designed with three separately controlled circuits. The outer ring of 5 LEDs could be separately turned on and off in order to "brighten" the target (Fig. 2). The inner ring of 5 LEDs also included the IR LED. When a target was activated, this circuit would turn on (Fig. 3). Lastly the infrared phototransistor was separately connected to a signal conditioning circuit and was always active (Fig. 4). Finally, the conditioning circuit outputs a digital high/low square wave when it sees a hand (Fig. 5).