Designing a Multi-purpose GSM Based Interactive Embedded Data-Acquisition System Providing Solutions for Fire Accidents

The Data-Acquisition systems with remote accessibility are greatly demanded in industry and consumer applications. In this paper, a data-acquisition system which can save lives and property, based on GSM communication, accommodating a wide range of electronic devices is presented. The system has the special ability to automatically quench fire by spraying water during fire accidents, simultaneously informing the local fire station and the responsible persons as well, saving loss of life and property. Also the varying status can be instantaneously recorded and uploaded in internet, for failure analysis. By using a GPS receiver it is possible to acquire and display the images of the locations where there are fire accidents by decoding the text SMS data, which helps in continuously tracking the fire accident location using google maps, helping the fire engine to reach instantly. Also the cost-effectiveness of the overall system is proved. The embedded board acts as the main controller of this system which has a SIM card placed in it and thus communicates using GSM, making it accessible from anywhere in the world, providing a faster two-way data transfer between the Embedded system and the client, in real-time

Design and Implementation of Low Offset Sensor Interface for Differential Capacitive Sensors

Nowadays, due to advancement of micro fabrication technology, Micro-Electro-Mechanical-Systems (MEMS) based miniature sensors are becoming more popular. But sensing physical variables, which are analog in nature, with these sensors is a challenging task. Among different type of MEMS based sensors, capacitive sensors are preferred for the measurement of displacement, pressure, acceleration etc. in various applications ranging from bio-medical devices to automotive safety. An integrated capacitive sensor system comprises of a capacitive sensor and a signal conditioning circuit, which provides electrical output as a function of change in capacitance (ΔC). These sensors offer several advantages such as smaller size, lower power consumption, higher sensitivity, lesser temperature coefficient and compatibility for monolithic integration. But due to micrometer dimension, these micro capacitive sensors provide very small change in capacitance, in the range of few femto-farad (fF). Detection of such small capacitance in the presence of considerable parasitics is quite challenging. Moreover, non-idealities of the interfacing circuit components, such as DC offset, 1/f noise, kT/C noise etc. limit the performance of the system. Chopper modulation, Auto-zeroing, Correlated Double Sampling etc. are quite popular to improve the performance of the interfacing circuit. In this work, we have proposed five switched capacitor based interfacing circuit topologies, which reduces the non ideal effects of the circuit components. Apart from these five configurations, we have also proposed an auto-calibration method to reduce the offset from sensor mismatch which can be implemented fully on-chip. These interfacing circuits are analysed theoretically and simulated using spectre simulator in Cadence Virtuoso environment. Among five interfacing circuits, four are designed and fabricated in UMC 180 nm CMOS process technology and the fifth one is designed in SCL 180 nm CMOS process technology. The fabricated UMC IC is integrated with a SOI MEMS capacitive acceleration sensor and measurement is carried out. Static characterization of the fabricated IC is carried out with the help of on-chip capacitors and the dynamic testing of the integrated system is done by a custom-made vibration setup with a sub-woofer system. The static and dynamic measurement results along with the merits and demerits of the proposed interfaces are reported in this thesis

Advancing frequency locking : Modified FPGA-Guided direct modulation spectroscopy for laser stabilization

In this paper, we propose a cost-effective laser frequency locking scheme based on frequency modulation spectroscopy (FMS) for precision measurements and experiments in various fields. We demonstrate that by digitally modulating the detected signal frequency using a Field-Programmable-Gate-Array (FPGA) driven by a home-built lock-in and a proportional–integral–derivative (PID) control system, our system achieves higher precision, user-friendliness, and versatility. Our system generates a 20 V peak-to-peak amplified voltage to a piezo transducer (PZT), which enables a mode-hop free laser scan of approximately 2 ±0.2 GHz. We directly modulate the detected saturation absorption signal with a sinusoidal waveform, then demodulate it to obtain multiple zero crossing locking points on the D2 transition of Cs at 852.35 nm. We optimized the system for three commonly used atomic transitions and found that researchers can select any of the zero crossing peaks for frequency stabilization depending on their experimental requirements, we locked the laser at the crossover transition. We measured the long-time frequency fluctuation and power spectral density and found that the frequency fluctuation of the laser is much less than the natural line width of the D2 transition of Cs. Our results demonstrate that our laser frequency locking scheme is effective and practical for precision measurements and experiments in various fields.Peer reviewe