Projects

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.

Imagine your self with out the knowledge of English or other modern languages. How will you use a computer? How can you e-mail a friend, browse the Internet, or listen to MP3 on line? You can not. In some cases the limitation extends to entire societies who lack the Information and Communication Technological (ICT) infrastructure needed to support computing in their respective languages. Just like reading, writing, and numeracy, computing is a sphere of modern life that no human can afford to ignore.

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.

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.