A common voltage-controlled oscillator (VCO) architecture used in the phase locked loop (PLL) is the ring oscillator (RO). RO consist of number of inverters cascaded together as the input of the first stage connected to the output of the last stage. It is important to design the RO to be work at desired frequency depend on application with low power consumption. This paper presents a review the performance evaluation of different delay cell topologies the implemented in the ring oscillator. The various topologies analyzed includes current starved delay cell, differential delay cell and current follower cell. Performance evaluation includes frequency range, frequency stability, phase noise and power consumption had been reviewed and comparison of different topologies has been discussed. It is observed that starved current delay cell have lower power consumption and the different of the frequency range is small as compared to other type of delay cell.

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This paper describes the design and development of a shoe dryer using a microcontroller. Nowadays, people often travel and sometimes in rainy day, they need to dry their shoe in a very short time anywhere. However, very rare of places including shopping mall and hotel provide a shoe dryer. The shoe dryer is designed to help people who are in hurry to dry their shoe on the go. A temperature sensor is used to measure the temperature inside the shoe dryer, while a program is uploaded in the microcontroller for reading and data collection. The programming includes the activation of shoe dryer with the GSM module, thus it can be controlled using a mobile phone. An experiment was conducted to test the performance of the shoe dryer. The optimum performance was obtained when the temperature is set at 36°C, and timer at 60 seconds with normal room temperature. The temperature and timer need to be adjusted accordingly based on the shoe condition in order to get very satisfying results. This paper proved that the shoe dryer was successfully designed, implemented and analyzed.