3 Optical density based polarization sensor (BT) J Bellare(chem engg)

This is a project related to a sensor needed in the processing of materials whose optical properties are affected by the processing. For example, in the production of plastic films, the extent of stretching of the film determines it molecular orientation and hence its strength. However, overstretching it can result in reversal of properties. So, an optimal stretch is needed. How to sense this optimum? It turns out that the stretch also affects the optical properties of the materials, specifically, its polarization state. This, in turn, can be sensed of noting the intensity of light falling on two photodiodes/transistors, and the extent of stretch noted by matching the intensities by rotating a suitable optical filter in fromt of the photosensors. This, the device you will have to build will have a light source, a fiber-optic light guide, a filter, a light-sensor pair, a comparator (instrument diff amp), and a microcontroller that senses the difference and drives a stepper/servo motor and displays the angle through which the filter had to be moved to make the intensities equal.

4 High voltage constant-current/constant voltage supply (BT) J Bellare(chem engg)

Such power supplies are needed in biotechnology applications for projects like the genome project, protein studies and the like. A high voltage is applied across the two opposite edges of a sheet of porous material like a gel or a filter paper. The gel has in it the material of interest, e.g., the protein mixture. The proteins move under action of the current, and this is used to perform analysis and separations. Various modes are needed: constant voltage, constant current, and constant power. Safety is also a concern, as the voltages could be high, and the device used in wet environments. This project is eminently suited for commercial production if perfected. A inverter design will be prefered, with a design frequency of about 50kHz. Control circuit design, magnetics design and system integration will all be important.