Making an efficient but cost-effective automated goniometric device for a light-scattering study

Abstract

A goniometer is an instrument which is frequently used in optics and other branches of physics. It enables the study of light scattered in various directions from a solid, liquid or powdered sample. The goniometric instruments that are already available on the market are designed for a specific purpose and are quite costly. Fully-computerized devices—which automatically acquire data and control the positions of the light source and detector—are even more expensive. In this work, the instrumentation of a self-fabricated, low cost, but fully computerized goniometric instrument designed for studying a light-scattering problem in planetary science is described in detail. This device uses Arduino microcontroller boards for acquiring data, and stepper motors are employed for automated control of the positions of the light source and detector. A low-cost but high-intensity laser diode was used as the light source, and a very sensitive photodiode integrated circuit was used as the light detector. This work has a pedagogical value in the sense that the reader will benefit from learning about the techniques used, the components and their calibration, the software, etc. More importantly, the cost-effectiveness of this work may be beneficial to many experimentalists and instrument designers working in this field, to control their project budgets.