Maman Budiman

Home‐made PIC 16F877 microcontroller‐based temperature control system for learning automatic control

A closed‐loop temperature control system, which is composed of a thermal plant and a controller, has been developed to support undergraduate students in learning automatic control delivered in the Special Topics in Instrumentation Physics course. The thermal plant was made from a plastic box covering a lamp and a fan, which heats and drains the air in the plastic box, respectively, as well as a temperature sensor. The controller with a proportional control action was realized by employing the PIC 16F877 microcontroller. The control signal updates pulse‐width modulators (PWMs) in which driver circuits turn on or off the lamp and the fan. A mathematical model of the closed‐loop control system was derived and a theoretical transient response was then obtained. It is found that the experimental transient responses were always much lower than the set point and the steady‐state errors were high for the proportional sensitivity (KP) lower than 10. For KP higher than 10, the transient responses tend to approach the set point to cause small steady‐state errors. These characteristics are consistent with the theoretical transient response. Further examination revealed that the closed‐loop system is a higher order system due to the action of the PWMs and the driver circuits.

A simple spectrophotometer using common materials and a digital camera

A simple spectrophotometer was designed using cardboard, a DVD, a pocket digital camera, a tripod and a computer. The DVD was used as a diffraction grating and the camera as a light sensor. The spectrophotometer was calibrated using a reference light prior to use. The spectrophotometer was capable of measuring optical wavelengths with a theoretical accuracy as high as 0.2 nm. Using this spectrophotometer, wavelengths are determined via image processing.

An AT89S52 microcontroller-based single board computer for teaching an instrumentation system course

A single board computer (SBC) based on the AT89S52 (a member of MCS‐51 family) microcontroller with an ADC, serial and parallel communications, and input/output devices such as a pushbutton, a keypad, LEDs, 7‐segment displays, and an LCD was developed for teaching an instrumentation system course to the sophomore students. Five microcontroller‐related laboratory experiments offered to the students within the 15‐week semester are (i) basic programming of the microcontroller, (ii) interfacing the DIP switches, LEDs, and 7‐segment displays, (iii) application of the analog multiplexer and the ADC with the LCD, (iv) serial communication and application of the HyperTerminal, and (v) measurement of water temperature, displaying the measurement result, and application of the LabView.

Development of digital water meter infrastructure using wireless sensor networks

Digital water meter infrastructure was developed to reduce weakness of the existing system, inaccurate, difficult to access and takes time to collect the data. The system has a distributed wireless network of water meter sensors placed in the mechanical device. The number of pulses will be counted by the microcontroller then sent by using Nordic NRF24. It is a communication module that works at a frequency of 2.4 GHz ISM. Its main advantage is that a mesh network can be built through the development of algorithms. To connect each cluster of the mesh network, a gateway was also developed. The system has successfully monitored the volume of water in real time and can be accessed by utilities and costumers.

Design of 3D scanner for surface contour mapping by ultrasonic sensor

Surface mapping systems have attracted great attention due to their potential applications in many areas. In this paper, a simple 3D scanner based on ultrasonic sensor was designed for mapping a contour of object surface. The scanner using an SRF02 ultrasonic sensor, a microcontroller and radio frequency (RF) module to collect coordinates of object surface (point cloud), and sent data to computer. The point cloud collection process was performed by moving two ultrasonic sensors in y and x directions. Both sensors measure a distance from an object surface to a reference point of each sensor. The measurement results represent the point cloud of object surface and the data will be sent to computer via RF module. The point cloud then converted to 3D model using MATLAB. It was found that the object contours can be reconstructed very well by the developed 3D scanner system.

High Performance Current-Voltage Characterization System for High Resistance Materials

The resistivity measurement finds many applications in semiconductors and insulating materials characterization. Conventional digital multimeter can provide resistance measurement up to about 10-200MΩ. However, in some cases, resistances in gigaohms (GΩs) and higher ranges need to be measured accurately. To measure the resistance of high resistivity materials, a programmable voltage source (-100V to +100V) combined with an electrometer system (100pA 10mA) have been built. The electrometer system and programmable voltage source have been calibrated with a calibrator (Fluke 5100B series) and digital multimeter (Fluke 8808A). Materials resistance up to 10 GΩ can be obtained by measuring the current-voltage (I-V) characteristics. It is found that the I-V curve of the 10 GΩ resistor fits very well the linear function with a high linear regression coefficient R2 of 0.999.

Optimization of Coating Temperature of TiO2 Nanoparticles on the Polypropylene Copolymer Surface for Photodegradation of Methylene Blue

TiO2 nanoparticles have been coated on the polypropylene (PP) copolymers using a milling method with temperature controller modification. These experiments were carried out at different milling temperature: 100 °C, 110 °C, 120 °C and 130 °C for 90 minute milling time for each experiment. Photocatalytic degradation of methylene blue (MB) was investigated using TiO2 coated PP copolymer which floats on the MB solution and illuminated under sunlight for 36 hours. It was found that TiO2 coated PP polymer at temperature of 100 °C resulted in optimum decomposition of MB solution. The concentration of MB in a test solution after 18 hours of exposure to the sun was 15.42%. The reaction rate constants (k) and the half‐reaction (t1/2) in the MB photodegradation using the catalysts with a coating temperature of 100 °C, are 0.106 hours−1 and 6.53 hours, respectively. This coated material is very potential for repeated use to purify bulk water in high sunlight intensity region.

Growth of Al x Ga 1−x N epitaxial thin film on sapphire substrate by plasma assisted metal organic chemical vapor deposition (PA-MOCVD)

This paper reported the study of growth of AlxGa1−xN thin film on a-plane sapphire substrate using plasma assisted metal organic chemical vapor deposition (PA-MOCVD). We have successfully growth the Al content AlGaN alloys and investigated the influence of TMA/TMAl+TMGa flow rate ratio to their crystal structure and surface morphology. From S EM image and XRD measurement, the AlGaN films grown with TMA/TMAl+TMGa flow rate ratio of 20% have single crystal orientation, homogeneous and smoother surface morphology. From ED X microanalysis results, all of the AlGaN alloys have high Al content. The Al content of the AlGaN alloys with TMA/TMAl+TMGa flow rate ratio of 20%, 30%, and 40% is about x = 0.5, 0.6, and 0.65, respectively and grown at the growth temperature about of 700°C.

Microstructure and Optical Properties of AlxGa1−xN/GaN Heterostructure Thin Films Grown on Si(111) Substrate by Plasma Assisted Metalorganic Chemical Vapor Deposition Method

Microstructure and optical properties of AlxGa1−xN/GaN heterostructures thin films grown on Si(111) substrate by Plasma Assisted‐Metalorganic Chemical Vapor Deposition (PA‐MOCVD) were investigated. The surface morphology and crystal orientation of the films were determined by scanning electron microscope (SEM) and X‐ray diffractometer (XRD), respectively. The content of Al in AlxGa1−xN films (x) was determined by means of NIR‐UV visible optical reflectance spectroscope. The surface morphology of films depends significantly on the content of Al. Films with higher value of x showed the smaller grain size and the smoother surface. Films with x = 0.29 and x = 0.36 showed crystal orientation of (101 0) plane, while films with x = 0.12 have two crystal orientation of (101 0) and (101 1) planes. The optical reflectance spectra showed that the ordered of oscillation depend on the smoothness of the film surface, while the number of oscillation related to the thickness of films. The calculated band gap was 3.34 ...

Study of Mg‐doped GaN Thin Films Grown on c‐Plane Sapphire Substrate by Plasma Assisted Metalorganic Chemical Vapor Deposition Method

Mechanism of doping of Mg in GaN thin film grown on c‐plane sapphire substrate by plasma assisted‐metalorganic chemical vapor deposition (PA‐MOCVD) method have been investigated. The growth was carried out at temperature of 680 °C, which flow rate of Cp2Mg as dopant source was varied of 0.003; 0.006; 0.009 and 0.012 sccm. The Van der Pauw technique, X‐ray diffraction (XRD) and scanning electron microscope (SEM) were used to characterize their electric, crystallographic and morphology properties. Hole concentrations of up to 1019 cm−3 have been observed for Mg‐doped GaN films without any post‐growth annealing. The XRD analysis showed change of the FWHMs for the (0002) orientation plane from Mg‐doped GaN films. The difference of the atomic radius between Ga and Mg atoms causes lattice distortion in crystal. This lattice distortion generates dislocation and causes growth of the layer to be three‐dimensional as showed on SEM images.