Wireless Data Transmission – Big Picture

Wireless data transmission is achieved via optical means utilizing receiver and transmitter units. The transmitter unit consists of a laser diode and supporting power and switching circuit. The laser diode is supplied power from an Arduino. The 3.3V from the Arduino is voltage divided to near 3.0V to match with the laser diode specifications. The 3.0V is provided for the diode through a transistor, which also functions as a current switch controlled by software running on the Arduino. The circuit is used by the microcontroller to transmit binary data in the form of diode off (0) and diode on (1). The data is transmitted common asynchronous serial format (8N1). The receiver unit consists of photoresistors and an accompanying resistive circuit, arranged in a Wheatstone Bridge configuration. An Xplained Mini Board then uses both points ‘D’ and ‘B’ in the circuit to measure signal strength; one as a reference to ambient light, the other as a measure of ambient light plus signal light (i.e laser diode light). The Xplained Mini Board then decodes the bits received (8N1) and extracts the data bits, finally translating them back into ASCII characters that can be displayed via the serial terminal on the connected host device; TeraTerm in the case of this experiment