Application of the photodiode in design and implementation of a 2-D position detector

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Virginia Tech

The goal of this project is to design and build a 2-D position sensing system. The design is composed of three major tasks: (1) design of the optoelectronic circuit, (2) design of the data acquisition and control circuit and (3) design of the system software. For the major sensor, the SC-10D photodiode manufactured by the United Detector Technology Inc. (UDT Sensors) is used, and for the system controller, the 8051 microcontroller manufactured by Intel is used.

During the operation, the current output from the SC-10D is converted into a voltage signal by operational amplifiers, and then converted into an 8-bit digital signal by the ADCO809 analog-to-digital (A/D) converter. The 8-bit data is then transmitted through the RS-232C channel to a host computer where numerical processing of the data is performed and the position values are displayed on the CRT screen. The system can detect the 2-D position of a small light source at 2 to 3 m. Methods of improving the resolution and the operating distance are also explored. The functional block diagram is shown in Figure 2 [See document]