Smart Dust Seminar Report

                                             CHAPTER-1
                                                        

                                          INTRODUCTION

Smart dust requires mainly revolutionary advances in miniaturization, integration & energy management. Hence designers have used MEMS technology to build small sensors, optical communication components, and power supplies. Microelectro mechanical systems consists of extremely tiny mechanical elements, often integrated together with electronic circuitory. They are measured in micrometers, that is millions of a meter. They are made in a similar fashion as computer chips. The advantage of this manufacturing process is not simply that small structures can be achieved but also that thousands or even millions of system elements can be fabricated simultaneously. This allows systems to be both highly complex and extremely low-cost.

Micro-Electro-Mechanical Systems (MEMS) is the integration of mechanical elements, sensors, actuators, and electronics on a common silicon substrate through microfabrication technology. While the electronics are fabricated using integrated circuit (IC) process sequences (e.g., CMOS, Bipolar processes), the micromechanical components are fabricated using compatible "micromachining" processes that selectively etch away parts of the silicon wafer or add new structural layers to form the mechanical and electromechanical devices. MEMS realizes a complete System On chip technology.

            Microelectronic integrated circuits can be thought of as the "brains" of a system and allow microsystems to sense and control the environment. Sensors gather information from the environment through measuring mechanical, thermal, biological, chemical, optical, and magnetic phenomena. The electronics then process the information derived from the sensors and through some decision making capability direct the actuators to respond by moving, positioning, regulating, and filtering, thereby controlling the environment for some desired purpose. Because MEMS devices are manufactured using batch fabrication techniques similar to those used for integrated circuits, unprecedented levels of functionality, reliability, and sophistication can be placed on a small silicon chip at a relatively low costThe deep insight of MEMS is as a new manufacturing technology, a way of making complex electromechanical systems using batch fabrication techniques similar to those used for integrated circuits, and uniting these electromechanical elements together with electronics.Historically, sensors and actuators are the most costly and unreliable part of a sensor-actuator-electronics system. MEMS technology allows these complex electromechanical systems to be manufactured using batch fabrication techniques, increasing the reliability of the sensors and actuators to equal that of integrated circuits. The performance of MEMS devices and systems is expected to be superior to macroscale components and systems, the price is predicted to be much lower

Integrated into a single package are :-

MEMS sensors MEMS beam steering mirror for active optical transmission MEMS corner cube retroreflector for passive optical transmissionAn optical receiver Signal processing and control circuitory

A power source based on thick film batteries and solar cellsThis remarkable package has the ability to sense and communicate and is self powered. A major challenge is to incorporate all these functions while maintaining very low power consumption.

·       Sensors collect information from the environment such as light , sound, temperature ,chemical composition etc

·      Smart dust employs 2 types of  transmission schemes:-passive transmission using corner cube retroreflector to transmit to base stations and active transmission using a laser diode & steerable mirrors for mote to mote communication.

·       The photo diode allows optical data reception

·       Signal processing & control circuitory consists of analog I/O ,DSPs  to control &process the incoming data

·       The power system consists of a thick film battery,a solar cell with a charge integrating capacitor for a period of   darkness.

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