A solar simulator suitable for universities' lab was designed and developed using a quartz tungsten halogen lamp as its light source, an alternating current phase-cut dimmer, a light intensity meter, and an ATMega328p microcontroller with a computer and a liquid crystal display. Noting that the quartz tungsten halogen lamp suffers bulb overheating and longterm degradation that leads to the decrease in its light intensity, a control mechanism was applied. The control mechanism employed a proportional-integral-differential action with Some-Overshoot Ziegler-Nichols tuning rule. It was shown that the control mechanism works well in stabilizing the quartz tungsten halogen lamp irradiance between 273 and 1182 W/m 2. The developed solar simulator was then tested to obtain I-V (current-voltage) characteristics of 3 W peak and 5 W peak commercial solar panels (GH Solar, GH5P-9). Based on the gained I-V characteristics, it was shown that the obtained characteristics of the commercial solar panels are in the range of the characteristics provided by the manufacturer's data sheets. The developed quartz tungsten halogen lamp-based solar cell simulator can therefore be used to characterize solar cells.

According to WHO, indoor and/or outdoor air pollution is one of the main contributors to over two million premature deaths each year. As most of the human's life is spent indoor, Indoor Air Quality (IAQ)-an air quality inside of a building represented by pollutant concentration and thermal condition-is one factor that needs to be concerned to sustain healthy living. In this research, we developed an Internet of Things (IoT)-based IAQ monitoring device using low-cost sensors that measure the concentrations of Carbon Dioxide (CO 2), Oxygen (O 2), and Particulate Matter (PM 2.5). This device connects to an Android application to further observe these parameters inside two practicum laboratories in Telkom University, Bandung, for a total duration of six weeks. The location is surrounded by urban air pollution, particularly industrial activities, and residential waste burning. We also have sites of outdoor air quality monitoring system for simultaneous measurement. The environmental conditions were observed under no human activities, human intervention, and indoor plants' influence (i.e., Dieffenbachia sp.). Results show that pollutant concentrations are considerably influenced by outdoor conditions, occupancy level, and ventilation rate. Indoor plants can reduce CO 2 concentrations inside the room (21-47%). On the other hand, there is no clear evidence that PM 2.5 mass concentrations were affected by human activities. The bigger particles (PM >2.5 microns) probably were the ones induced by occupants during practicum. Therefore, using low-cost sensors is trustworthy to monitor IAQ for a better quality of life.

Field observation of PM2.5 and CO2 concentrations and meteorological conditions using low-cost sensors in real-time was carried out in the Greater Bandung air basin on Mar. 12 – Apr. 25, 2019. PM2.5 and CO2 sensors, as well as detectors of meteorological parameters, have been calibrated in the Laboratory. The instruments were placed in two locations (±300 m apart horizontally and ±20 m vertically), namely Tokong Nanas Building (Location 1 / L1) and Deli Building (L2), Telkom University, Bandung. Data was stored in the data logger and sent to the cloud database every 2-min through the GSM module. The results show that the same air mass in both locations has identified, except for some events that are affected by anthropogenic activities (those concentrations in L2 L1) and wind speed/direction (time delay). The daily-average PM2.5 and CO2 concentrations at L1 and L2 are 52 µg m-3 and 580 ppm, and 70 µg m-3 and 809 ppm. PM2.5 and CO2 mass concentrations relatively higher (±172 µg m-3 and 916 ppm) at night due to a stable atmosphere (potential temperature, dθ/dz 0, typical data from 20:00 to 3:00 local time), lower planetary boundary layer, and mixed local emissions and transboundary air pollutants. Meanwhile, lower CO2 concentrations in daytime mostly occur due to the activity of vegetation, which actively absorbs CO2 in the photosynthesis process. The fluctuation of those concentrations due to polluted air suggests that the performances of low-cost sensors can be adequately used properly for ambient air quality monitoring. Keywords: CO2, low-cost sensors, PM2.5, potential temperatureABSTRAKPemantauan konsentrasi PM2.5 dan CO2 serta kondisi meteorologi berbasis low-cost sensors secara real-time di cekungan udara Bandung Raya telah dilakukan pada 12 Maret-25 April 2019. Sensor PM2.5 dan CO2, serta detektor parameter meteorologi telah dikalibrasi di Laboratorium. Alat ukur ditempatkan di dua lokasi dengan perbedaan jarak ±300 m dan ketinggian ±20 m, yaitu Gedung Tokong Nanas (Lokasi 1 / L1) dan Gedung Deli (L2), Universitas Telkom, Bandung. Komunikasi data menggunakan modul GSM (SIM900A) dan data disimpan di data logger dan dikirimkan ke cloud database per 2 menit. Hasil pengukuran menunjukkan bahwa massa udara di kedua lokasi memiliki tren data konsentrasi PM2.5 dan CO2 yang relatif homogen, kecuali pada beberapa kejadian yang dipengaruhi oleh aktivitas antropogenik (konsentrasi PM2.5 dan CO2 di L2 L1) serta arah dan kecepatan angin (adanya perbedaan konsentrasi massa PM2.5 akibat penundaan waktu). Rerata harian konsentrasi PM2.5 dan CO2 di L1 dan L2 berturut-turut adalah 52 µg m-3 dan 580 ppm serta 70 µg m-3 dan 809 ppm. Konsentrasi massa PM2.5 dan CO2 yang relatif lebih tinggi (±172 µg m-3 dan 916 ppm) di malam hari akibat atmosfer yang lebih stabil (temperatur potensial, dθ/dz 0, tipikal dari pukul 20:00-03:00), penurunan planetary boundary layer, dan terjadinya pencampuran partikulat lokal dengan polutan udara lintas batas. Sedangkan, konsentrasi CO2 yang relatif lebih rendah di siang hari sebagian besar terjadi akibat aktivitas vegetasi yang aktif menyerap CO2 pada proses fotosintesis. Fluktuasi konsentrasi karena udara tercemar menunjukkan bahwa kinerja low-cost sensors dapat digunakan dengan baik untuk memantau kualitas udara di atmosfer.Kata kunci: CO2, low-cost sensor, PM2.5, temperatur potensial

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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.

Water surface level should get special attention as water can cause disasters such as flood when its surface exceeds a certain level. A real time early warning system to monitor water surface level is necessary for avoiding severe effects of flood to human life. A web-based water level measuring system using an ultrasonic sensor can be an alternative choice for developing the early warning system. It is known that the system has advantages in the installation and maintenance compared to other systems. This paper discusses the design of a water level measuring system integrated with an internet web server. Ultrasonic sensors are used to measure the water surface level. A GSM / GPRS-based communication system is applied for sending measured water levels to a web server. The results indicate that the measurement data are in accordance with the water levels manually obtained. The results also show that the system works real time.

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