Hardware Design and Software Development for a White LED-Based Experimental Spectrophotometer Managed by a PIC-Based Control System

In this paper, the design and testing of a PC-interfaced PIC-based control unit used to manage an absorption spectrophotometer, employing a white LED as light source, are described. LED technology allows to perform the absorption measurements reducing the analyte temperature variations and thus noise generation, which occur if a Xenon light source, usually employed, is used; also thanks to LED technology, the system results low cost, easy to use and with a low power consumption. The realized spectrophotometer can be used for atmospheric and industrial pollutant detection or for indoor air monitoring (e.g., in hospital rooms), being able to detect particulate matter, pesticides, volatile organic compounds as well as pollution produced by heavy metals. The realized system manages the different required functionalities, such as acquisition and processing, via firmware, of raw data provided by sensors, actuation of mechanical devices (stepper motor and solenoid valve), and synchronizing and controlling the data exchange between hardware sections, microcontroller, and PC. Both hardware and software sections were designed carrying out the appropriate tests to verify their proper operation. Results confirm the correct system functioning and interaction, via PC terminal, between user and the realized control unit.