Applied Mechanics and Materials Vol. 771

Abstract: The development of a wireless sensor network system for temperature and humidity monitoring is described. The system is composed of two main parts, namely an end device and a coordinator. The end device consists of an SHT10 sensor, an XBee Pro RF module, an ATMega8535 microcontroller, and a battery. The coordinator consists of an XBee Pro RF module and an SIM900 GSM module. The temperature and humidity data were sent by the end device to the coordinator and they were forwarded to the web server via GPRS communication using the SIM900 GSM module. In order to the data stored in the database can be accessed in real time via the internet, a web server is developed by using CodeIgniter (CI). It was shown that each end device can communicate very well with the coordinator. Moreover, the data are received in accordance with the timing of delivery was given.

Abstract: A circuit for generating triangle waveform with variable, digitally controlled frequency has been developed. The circuit utilizes a Cygnal C8051F005 System-on-a-Chip (SoC) for controlling the output frequency. Two 12-bit Digital to Analog Converters (DACs) included in the SoC feeds a voltage to a frequency converter to generate symmetrical bipolar triangle signal using four op-amps, which is an improved version of commonly found voltage controlled oscillator circuit. With one DAC, the frequency can be swept from 7 Hz to 3000 Hz while the amplitude remains constant. The second DAC is used to fine tune the frequency. The circuit also outputs synchronous square wave for frequency measurement by the SoC. The circuit was applied for testing or characterizing electronic devices or samples with fully digital control input from the user.

Abstract: A portable electronic nose (e-nose) using low-cost dynamic headspace and commercially metal oxide gas sensors has been developed. This paper reports evaluation on the performance of the e-nose to classify vegetable oils (sunflower and grape seed oils) and animal fats (mutton, chicken and pig fats). The e-nose consists of a dynamic headspace sampling, a gas sensor array and a real-time data acquisition system based on ATMega-16 microcontroller. The dynamic headspace can divided into two chambers, i.e. sample and gas sensor array room. It is also equipped with three small fans for adjusting sensing and purging processes. Principal component analysis (PCA) was used for measurement data analysis after all features being extracted. The first two principal components were kept because they accounted for 91.1% of the variance in the data set (first and second principals accounted for 72.9, 18.2% of the variance, respectively). This results show that the e-nose can distinguish vegetable oils and animal fats. This work demonstrates for the future that the e-nose with low-cost dynamic headspace technique may be applied to the identification of oils and fats in halal authentication.

Abstract: Fluxgate sensor has high sensitivity and temperature stability, small size and low power consumption. Fluxgate sensors can often provide very useful alternative in determining the location or position of a magnetic object, where other technologies cannot be used. For example, the GPR only, does not provide maximum results when used to characterize the magnetic material in the conductive subsurface or has a high reflectivity zone, but fluxgate sensors are capable. Characterization of magnetic materials in the soil subsurface is required. It is used as a proxy to determine the content of heavy metals and pollutants in the soil. In this work, we have carried out the development of fluxgate sensors for detection of magnetic material in soil subsurface. The fluxgate element consists of two pick-up coils, four excitation coils, and the ferromagnetic core. The highest sensitivity of fluxgate sensors that have been developed is 877 mV/µT and a maximum absolute error of 0.066 mV/µT. This paper will discuss the influence of the frequency of the primary magnetic field of the solenoid on the sensor response, the influence of soil magnetic susceptibility, and the effect of the presence of magnetic material in the soil subsurface to the sensor response.

Abstract: In this paper, the FTC system for multiple operating condition nonlinear systems subjected to sensor faults is developed by applying reconfigurable control scheme. The scheme generates any modified control signal using appropriate additive reference signal to the nominal control system. The proposed observer is developed based on descriptor approach in the fuzzy Takagi-Sugeno model configuration in order to accommodate some operating conditions of a nonlinear system. The simulation result shows that the proposed method has capability to compensate more than one sensor fault occurred in a three-tank benchmark system even there is a change in condition operation as well as in reference signal.

Abstract: A study on the effect of light illumination introduced to the leaves of Mimosa pudica was carried out using different light intensities. The leaves will open gradually from the closed condition after the light was illuminated. Plant of M. pudica was placed in the dark box during measurement meanwhile the Petiole (part of the stem) of the plant was at normal position (hanging up). The camera was fixed to the box to monitor the leaves’ movement continuous and real time. By using this method the change of the top view area of the leaves could be observed. A crossed line was drawn on the image recorded and was measured its length. The calculation of the length gives the percentage of leaves at open during the observation time. Ultrasonic apparatus was also used to monitor the change of leaves. From the results, at an illumination intensity of 200 Lux, the percentage of leaves to open completely with respects to the observation time was found to increase nonlinearly by taking the time of 25 minutes. For intensities of 400 Lux, the trend of curve was also similar but increase rapidly. The ultrasonic signals show much stable at 200 Lux comparing to 400 Lux that was fluctuating. That may be due to the relatively faster movement of the leaves to open. This natural phenomenon is interesting and may introduce any change of natural indication that could be explored for further applications.

Abstract: One of the problems in intelligent mobile robot fire fighting contest is how the robot can find and can extinguish a fire without alot of sensors. The fire is located in a white circle area at one of the corner in room with random combinations. The way to solve this problems is conventional method-called-wall tracing. The robot uses wall tracing method to navigate, when entering the room this method still in used by the robot until its find the fire spot then uses one additional sensor to detect the white circle area where the fire located at. After detecting the white circle area, the robot will extinguishes the fire. This paper proposed a new method as optimization of conventional method. The proposed method is implementation of current algorithm (proportional derivatives algorithm) not only to wall tracing but also to TPA81 sensor (fire tracing) -called-wall and fire tracing method. Furthermore, this method is combination method between wall tracing and fire tracing. The robot will approach directly to the fire without wall tracing and without detecting white circle area. Then, the robot extinguishes the fire quickly. The robot uses only TPA81 sensor that can be used to detects the fire spot and its position in the room. Test result shows that 50% of the fire position variation on Indonesian Intelligent Robot Contest can be optimized using this method.

Abstract: A quantification of skin surface is one of challenging problem which is required in skin health assessment and efficacy evaluation of cosmetic products. Due to limitations of direct visual assessment of skin microscopic topography, an optical dermastocopy is commonly used as skin imaging device to magnify skin topography based on a white light reflection. The limitation of this method is its poor spatial resolution to quantify skin topography. In this paper, a skin imaging based on photometric stereo is proposed to visualize microscopic topography of human skin. The prototype was developed based on modification of illumination source system on the digital microscope. The illumination system consists of 6 and 9 super-bright LED. Additional electronic circuit was integrated with illumination system in order to control LED so that it can light successively. After that, set of images acquired in different angle of illumination was recorded. All images will be reconstructed using software to obtain stereo images, which shows the depth of the surface. Implementation on skin surface profile performed on three test areas: the back of the hand and knuckle creases. Based on qualitative analysis, our proposed scheme of skin imaging based on photometric stereo is promising for surface profile measurement and imaging of the skin.

Abstract: This paper presents a fire sensor module which is powered by harvested energy from the surrounding environment. The complete system consists of a transmitter module that sources energy from a mini generator energized by wind and thermal energy. The presented green energy poweredfire sensor is environmentally friendly and can be mass produced at a very low cost. A prototype of the forest-fire sensor consisted of transmitter and receiver module of STM110 EnOcean Firma has been constructed. The fire-sensor module detects the presence of fire in the vicinity using an NTC (negative temperature coefficient) temperature sensor. The thermistor is mounted on the exterior of the prototype (casing) and its switch-temperature is set between 90°C and 95°C. A rapid rise in the temperature above the set switch-temperature causes a rapid change in the sensor resistance, indicating the presence of a nearby fire. In response, the sensor would send a telegram to the central station (receiver module).

Abstract: Diathermy is commonly used treatment method for pain relief in musculoskeletal tissue, rheumatisms, inflammation etc., by which the increased temperature in tissue induces better blood perfusion and quickens the healing process. But improper maintenance and incorrect handling might lead to degrade the output power or may cause serious burns, respectively. So correct regular QA measurements for the output power would be necessary, in order to give the correct and safe treatment plan. A suitable tissue phantom is then needed to accomplish this task. For this purpose, a glycerol-based solid tissue phantom has been self-fabricated with insertion of four precission temperature sensors (LM 35) at locations of of 1.0 cm, 1.5 cm, 2.0 cm, and 2.5 cm from the surface (each of which are 2 cm laterally separated). Prior calibration of these four sensors for temperature range of 20 - 50°C (using a calibrated temperature calibrator) show very good accuracy and precission properties. The phantom is then tested by exposing it with RF waves output of SWD unit with time variation of 2-14 min (step 2 min), and output power variation of 20% - 80% of its maximum power (incremental step of 20%).