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Active Filter Design

A filter allows for useful frequencies of electronic signals to pass through while blocking or suppressing noise and unwanted frequencies. Using resistors, capacitors, and inductors filters can be designed. For low frequency filters op-amps instead of inductors are used, in order to avoid bulkiness and difficult production requirements. The later is called the active filter, and prior passive filter. Active filter design process is summarized in the block diagram.

Wave Form Generator

The aim was to analyze and implement a standard time-base wave generator that would produce 0 to 10 volts sawtooth and operate within the frequency of 100 to 1000 Hz. Also, 14 V p-p pulse waveform was required as an out-put. The circuit mainly consisted of hysteresis, which switched according to input from an integrator. The integrator was intern fed an adjusted output from the hysteresis. After analyzing systematically, the component values were determined and the circuit was implemented and tested part by part.

Phase Locked Loop

Phase Locked Loop is an important circuit found in various communication devices, and here studied in a set up to synchronize input and local carrier signals for coherent demodulation of AM signals. PLL consists of a phase detector, a loop filter, and a voltage controlled oscillator. The phase detector and loop filter combined produces an error signal which amplitude is linearly related to the phase difference of input and local carrier signals. The voltage-controlled oscillator adjusts appropriately to tune both signals as desired.

Temperature Measurement Device

Temperature is a physical quantity, which needs to be monitored for various applications. The design was part of a larger project where the data of humidity and temperature was to be recorded using a 68HC11 microprocessor over a week. The temperature sensor need to be within +/- 0.5 °c and function properly within the range of +30°c and -20°c.

Switch Mode Power Supply Implementation

The purpose was to construct a step-down switch-mode power supply with an output of 5v DC, and operative for current range of 0.1A to 1.0A. The design involved conversion, reduction, rectification, filtration and regulation of the standard AC voltage into the required output. A transformer was used to convert and reduce the AC input, and diodes were used for rectification. A RC network was used for filtering, and circuitry based on an IC pulse width modulator was used for voltage regulation.

Three phase Power Inverter

An inverter is a device that converts DC power into AC power. A three phase PWM controlled and sinusoidal output inverter is investigated. The specifications require a 10 KW output at a resistive full load of 4.8 W, and 220 volts line to line AC, rms. From the specifications a 37 A peak to peak to sinusoidal current was expected at the output. A standard topology of an three phase inverter consisting of three one-legged inverters was simulated using MATLAB/Simulink and Simulink Power Libraries. The current of 37 A and line to line voltage of 220 VAC, rms were adequately simulated. The resistive load is not a typical of many applications, thus need to be modified to model for inductive load.

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