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This script is work by research as finally project for to obtain predicate Bachelor Science (B.Sc) in field Instrumentation Physics entitled : "Controller System for Oscillation based on Computer Personal (PC) with Signals Digital to Analog Converter Approaching".

ABSTRACT

The harmonics oscillation is a simple performance for physical system.  Physical system usually vibrates in sinusoid wave, therefore oscillation system which is not in sinusoidal wave can be created from different sinusoid with different frequency and amplitude. Generations of pure sinusoidal oscillation in the physical instrument commonly experience distortion. Many methods have been used to generate pure sinusoidal wave such as using  precision analog component as well as using digital system.

This research aimed to design an interface DAC card I/O that has ability to convert digital to analog signal. This analog signal has electric voltage  that is proportional with digital value. The card is  stacked in one of computer expansion slots and has a function to control vibrating (trembling) Melde experiment. The  controlling system based on  computers consists of I/O interface with PPI 8255. A circuit, which converts digital signal to analog signal using a DAC 0808/MC1408 chip (with  conversion time 150 ns), and a sampling signals with  RC passive filtering component.

The DAC card has 5 V dc output. It   can generate oscillation at the frequency of 8 to 62 Hz. The DAC signal output is amplified by differential Op-Amp therefore can operate at Melde experiment with harmonics frequency of 11 to 60 Hz. The oscillation is generated with a software program written in Pascal. The software system for  Melde experiment consists of  harmonics generated mechanism, data display, data analysis, data saving and data/graph printing. The program, DAC card and PC operate in  compatible way, therefore it can give a control system which can be used as equipment/tool in teaching process, especially in teaching physics which employs demonstration method.

THESIS (MASTER) 

This thesis work by research at field Material Electronic for Engineering (Compoud Semiconductor) entitled : " A Study of Gallium Nitride of Thin Film Crystall Structure Grown By Plasma Assisted MOCVD Reactor."

ABSTRACT

Thin film Gallium Nitride have been grown on sapphire (0001) substrate by using Plasma Assisted Metalorganic Chemical vapor Deposition reactor. As the group III precursor were used trimethyl-gallium (TMG) from carrier of H₂ gases and N₂ gases as precursor group nitride and used to supply N radicals of N₂ gases, respectively. Growth to process preliminary grown by buffer layer using (TMG = 0,8 scam and N₂ = 90 scam) obtained film thickness about 0,025 m m. Next, parameter growth studied by temperature grown variation from 560 to 640 ⁰C, cleaning effect of substrates surface, and V/III ratio variation from 162,5 to 325. X-ray diffraction characterization result, obtained thin film of and with formed single crystal and wurzite structure (0002) for growth temperature 640 ⁰C and at V/III ratio 162,5 property of FWHM is 0,25 degree. From result ultra violet – visible (UV-Is) spectroscopy either obtained wide optical bandgap of thin film in spectrum at the 3,40 eV. Future work in study can fabricated high quality of thin films and other group III-nitride compound or heterostructure for optoelectronic devices.

Tujuan research ini lebih sebagai pengembangan studi lanjut (karier), pemahaman dan pengayaan kasanah ilmu, kompetensi dan wibawa karier, prospek hidup masa depan, dan planning studi lanjut doktoral (PhD). Ini dilaksanakan atas kemampuan beaya sendiri, jika Anda bersimpati menjadi sponsor akan diterima dengan senang hati. Adapaun riset yang sedang dan akan dikaji antara lain :