Controlling of DC-DC Buck Converters Using Microcontrollers

This paper presents a technique to digitally control the output voltage of a DC-DC converter via a microcontroller. The voltage regulation and controlling were achieved utilizing an LM2596 buck converter. A digital potentiometer MCP41050 is utilized to smoothly control the regulated output DC voltage via the SPI digital protocol. The proposed design is manufactured and tested for various loads. This device is considered as a step-down voltage regulator capable of driving 3A load with high efficiency, excellent linearity, source-voltage variation, and load regulation. The results show that the system can control the output voltage with satisfactory performance and high accuracy. With various loads, the proposed system shows a mean square error of 0.015±0.037 volts tested with a regulated voltage of 5 volts. The efficiency improves from about 80% to around 91% at a 1 kΩ load. This design eliminates the possible errors that arise when manually varying the voltage of the buck converter; by means of using a microcontroller. Such a system ensures a proper digitally controlled output voltage with a better performance, which can be applied in various applications.

Memristors as Candidates for Replacing Digital Potentiometers in Electric Circuits

Digital potentiometers are substantial components for the design of many mixed-signal electronic circuits and systems. Their capability to program resistance value almost instantly provides hardware designers an additional level of freedom. Unfortunately, this feature is limited to DC and lower frequencies, due to parasitic effects. Nowadays, memristors as continuously tunable resistors are becoming candidates for potentiometer successors. Memristors are two-terminal non-volatile devices which have less significant parasitic effects and a wide resistance range. The memristance value can be changed on the fly. Using nanotechnology, memristor implementation has a nanoscale footprint with nanosecond transition between resistive states. In this paper, we present a comparison between the frequency characteristics of digital potentiometers and the only commercially available memristors. Memristor parasitic effects dominate at higher frequencies which extends the bandwidth. In order to present the advantages of memristive circuits, we have analyzed and implemented tunable circuits such as a voltage divider, an inverting amplifier, a high-pass filter, and a phase shifter. A commercially available memristor by KnowM Inc. is used for this purpose. Experimental results obtained by the measurements verify that a memristor has equal or better characteristics than a digital potentiometer. Memristive realizations of voltage dividers and inverting amplifiers have a wider bandwidth, while filters and phase shifters with a memristor have almost identical frequency characteristics as the corresponding realizations with a digital potentiometer.

Pembangkitan Pulsa Orde Nanodetik Berbasis Mikrokontroler Untuk Eksitasi Transduser Ultrasonik

ABSTRAK Makalah ini melaporkan suatu teknik pembangkitan pulsa lebar orde nanodetik (ns) repetitif yang terprogram berbasis mikrokontroler untuk keperluan eksitasi transduser ultrasonik. Pembangkitan pulsa dan pengaturan jarak antar pulsa dilakukan melalui operasi timer mikrokontroler. Sebuah monostable multivibrator mengubah lebar pulsa dari mikrokontroler dalam orde nanodetik melalui pengaturan komponen pewaktuan resistor-kapasitor (RC) dengan cara pengaturan nilai R yang dibuat dari sebuah potensiometer digital. Hasil pengujian menunjukkan bahwa mikrokontroler membangkitkan pulsa repetitif dengan interval terprogram dalam orde 1 detik dan lebar pulsa minimum 1,25 ms. monostable multivibrator dapat mengubah lebar pulsa tersebut menjadi sekitar 140 ns. Berdasarkan hasil pengujian, dapat disimpulkan bahwa sistem berfungsi sesuai rancangan, sistem dapat membangkitkan pulsa repetitif dengan lebar pulsa hingga 140 ns dengan parameter interval dan lebar yang dapat diprogram. Kata kunci: generator pulsa, lebar pulsa singkat, mikrokontroler, monostable multivibrator, eksitasi transduser ultrasonik ABSTRACT This paper reports a repetitive, programmable, microcontroller-based pulse width generation technique for the purpose of ultrasonic transducer excitation. Pulse generation and distance adjustment between pulses is done through the microcontroller timer. A monostable multivibrator changes the pulse width of the microcontroller in the order of nanoseconds by adjusting the resistor-capacitor time constant which are done by adjusting the R value made from a digital potentiometer. The test results show that the microcontroller generates repetitive pulses with programmed intervals in order of 1 second and pulse width of 1.25 ms. A monostable multivibrator converts the pulse width to ca. 140 ns. Based on the test results, it can be concluded that the system functions according to the design as the system can generate repetitive pulses with pulse widths up to 140 nanoseconds with programmable interval and width parameters. Keywords: pulse generator, short-width pulse, microcontroller, monostable multivibrator, ultrasonic transducer excitation

Develop and implementation of PC based controller for humanoid robot using digital potentiometer

This paper introduced to develop and implementation of PC based controller for humanoid robot using digital potentiometer. The main objective in this paper is to develop and implement the joystick controller by using a digital potentiometer circuit board that be able to control the humanoid robot movement. The Arduino board and digital potentiometer will be integrated by connecting both pins in between wiper, W pin and ground, GND to the DB9 pins of remote control platform, which is TX and RX pins respectively. Humanoid robot as known as TOMY i-SOBOT is used as a preferred model due to wide usage in many applications. A digital potentiometer will be transmitted the voltage and current value depend on the digital level through serial communication to give the instruction for humanoid robot movement. The humanoid movement based on Guided User Interface (GUI) where the user give a commands by pressing the button on the GUI such as turn left, right, forward, and reverse. The results show that the humanoid movement able to control based on the voltage and current in a digital potentiometers value.

Mortality in Pacus (Piaractusmesopotamicus) caused by Pantoeaagglomerans and Pseudomonas aeruginosa in Excavated Tank

Background:Fish production in Brazil is growing strongly. This growth is being mainly driven by mainland aquaculture, which in 2017 produced 691.700 tons of fish. Toimprove production levels, fish farms have become increasingly intensive, but in these systems, the high fish densities in the ponds, the high feeding rate, and the high organic matter levels in the water can lead the fish becoming stressed. This can cause bacterial proliferationand an increase in mortality. Most species of fish-causing bacteria are saprophytes. They are found naturally in the environment and are usually responsible for secondary or opportunistic infections.Thisstudy reports on an outbreak of Pacus (Piaractusmesopotamicus) mortality at an intensive fish farm, in the municipality of Campo Grande, MS, Brazil,that used excavated tanks.Cases:The outbreak occurred at a fish farm in the municipality of Campo Grande, MS, during August, 2015. A total of 200 pacus in two tanks died after they showedthe following symptoms: lethargy, anorexia, increased mucus production, and disordered swimming and water surface searching. The temperature and dissolved oxygen were measured using a digital thermometer and an oximeter, respectively, and water transparency was measured with a Secchi disc. The pH was measured usinga portable digital potentiometer. The values for the water quality parameters analyzed during the mortality period were temperature, 22.5oC; transparency, 20cm; oxygen dissolved in the early morning 3mg/L and at the end of the afternoon, 4.5mg/L; pH 8.3; and toxic ammonia, 0.002ppm. Five fishes were collected from the tank, immediately cooled to 4°C, and sent to the Microbiology and Pathology Laboratories to perform the microbiological and pathological laboratory procedures.After the replication process, the slow glucose fermentation characteristics in MacConkey Agarand other biochemical tests showed that the lactose non-fermenter bacterium was Pseudomonas aeruginosa and the fermenting bacterium was Pantoeaagglomerans. A necroscopic examination revealed congestion of viscera in general and thickening of the gills; the histopathological examination showed an intense inflammatory reaction in the gills; andthe liver showed congestion and dilation of the central, hepatoportal, and sinusoidal veins,marked cytoplasmic vacuolization, the presence of hemosiderin and leukocytosis, and coagulation necrosis and cholestasis foci.Discussion:The water temperature in the tanks (22.5°C) was lower than what is considered ideal for tropical fish. It ranged from 25 to 32°C. Furthermore,the pH (8.3) was close to the limit of what is considered appropriate. The mean tank flow rate at the time of death was 15 L/min, corresponding to a daily renewal rate of 1.2%, which was lower than the 10% per day recommended as the ideal ratefor excavated ponds in a semi-intensive production system. The decreased water flow in the tank during the period when mortality was recorded caused an increase in the amount of accumulated organic matter. This rise is commonly referred to as eutrophication, which is characterized by an increase in the rate of decomposition and release of nutrients into the water. The excess nutrients, mainly nitrogen and phosphorus, cause excessive phytoplankton and aquatic macrophyte growth, which results in a significant reduction in the amount of dissolved oxygen, particularly during periods of low photosynthetic activity.In this case study, the cause of the fish mortalitywas attributed to opportunistic infection by Pantoeaagglomeransand Pseudomonas aeruginosacaused by imbalances in water quality.

Smart Antenna for Application in UAVs

In the present paper, a smart planar electrically steerable passive array radiator (ESPAR) antenna was developed and tested at the frequency of 1.33 GHz with the main goal to control the main radiation lobe direction, ensuring precise communication between the antenna that is implemented in an unmanned aerial vehicle (UAV) and the base station. A control system was also developed and integrated into the communication system: an antenna coupled to the control system. The control system consists of an Arduino, a digital potentiometer, and an improved algorithm that allows defining the radiation-lobe direction as a function of the UAV flight needs. The ESPAR antenna was tested in an anechoic chamber with the control system coupled to it so that all previously established requirements were validated.