Davor Vinko

Experimental Investigation of Symmetry-Breaking in Ferroresonant Circuit

This study focuses on the impact of circuit parameters on the breaking of steady-state symmetry in a ferroresonant circuit. Symmetry-breaking occurs owing to pitchfork bifurcation and results in the ambiguousness of steady-state solution through two possible waveform types. The two types are distinguished in this study by positive and negative peak values of capacitor voltage. Circuit parameters analyzed in detail are source voltage RMS value U1 and initial values of capacitor voltage and coil remanent flux. There is symmetry of occurrence in the two types of waveform, which is expected because of the odd symmetry of characteristics of all passive circuit elements. It is shown that the property of symmetry could be experimentally demonstrated and through simulation using a mathematical model of the experimental ferroresonant circuit. In addition, measurements have been carried out with two further coils to investigate the impact of the nominal voltage and type of core material on the initiation of the two types of waveforms.

Influence of Node Deployment Parameters on QoS in Large-Scale WSN

Quality of Service (QoS) support in large-scale Wireless Sensor Networks (WSNs) is becoming a hot topic in WSN area of research, primarily due to the fact that very complex problems need to be solved using resource constrained WSN nodes. On the other hand, with the large number of nodes in a network, a collective intelligence approach comes into focus for solving various issues. However, as node density and number increases various related problems comes into focus, such as increased RF interference on physical layer, large number of hops in data routing and the overall coverage area issue. All of these parameters are the result of WSN node deployment strategy and their influence on QoS cannot be neglected. To analyze this problem the paper simulated the behavior of large-scale WSN (up to 1000 nodes using OMNeT++) randomly deployed over an area of interest, based on deployment parameters (coverage area, number of nodes and TX power) and in respect to QoS metrics. From simulation results it can be concluded that deployment parameters substantially affects the QoS that a network can support. By choosing optimal deployment parameters it is possible to maximize QoS in a network.

Household power outlet overload protection and monitoring using cost effective embedded solution

With the widespread use of smart house systems monitoring power consumption in household applications is becoming a standard. In this scope a concept of a smart house or a home automation system is often characterized by the ability to control and monitor various household appliances to provide improved convenience, comfort, energy efficiency and security. In recent years costs of smart house systems are being reduced, however even for smaller systems they can be substantial (costs of installation, ongoing costs etc.). In this paper we propose a basic architecture for a smart house system targeted at increased safety and user awareness on power consumption. The main goal here is the design of cost effective solution used for monitoring power consumption at power outlets with the ability of user notification. The system has the ability to report instantaneous power consumption levels and issue a warning of a possible power overload. Communication component was realized using Power Line Communication (PLC) proposed communication protocol. Main advantages of the proposed system include low cost, overload protection and power consumption estimation at each power outlet, increasing user awareness resulting in more effective power consumption.

JavaScript virtual web page for wireless sensor node under AVR microcontroller architecture

This paper presents a developed wireless sensor node with an embedded JavaScript virtual web page implemented in the AVR microcontroller architecture. The presented design is capable of operating in real-time environment and has an improved performance with respect to the previously developed HTML virtual page. The major advantage of the presented system over the existing ones is the fact that the remote monitoring and control system is fully integrated in the microcontroller. The microcontroller is accessible over the Ethernet and with an integrated virtual web page it can replace the web server commonly used in similar systems. This feature makes the presented design extremely cost effective.

100 nA power management circuit for energy harvesting devices

This paper presents a power management circuit suitable for energy harvesting devices. Energy harvesting methods provide very low instantaneous power which is not sufficient to continuously power a wireless sensor node. Presented power management circuit is designed to turn on the wireless sensor node when the voltage across storage capacitor reaches 5 V and turns it back off as the voltage drops to 4.5 V. In such operating conditions maximal current that power management circuit draws is under 100 nA. Laboratory model of a power management circuit is realized and the performance measurements for various inputs were conducted. Additionally, a mathematical model of the power management circuit is derived and compared with measurement results.

Applicability of Dickson Charge Pump in Energy Harvesting Systems: Experimental Validation of Energy Harvesting Charge Pump Model

Energy harvesting methods provide very low instantaneous power. Accordingly, available voltage levels are low and must be increased so that an energy harvesting method can be used as a power supply. One approach uses charge pumps to boost low AC voltage from energy harvester to a higher DC voltage. Characterized by very low output current and a wide span of operating frequencies, energy harvesting methods introduce a number of limitations to charge pump operation. This paper describes and models behavior of Dickson charge pump in energy harvesting applications. Proposed Energy Harvesting model is evaluated and compared with Standard and Tanzawa charge pump models and with measurement results. Based on the proposed model, the conditions that need to be satisfied so that a charge pump can reach maximum power point of energy harvesting system are defined. Parameter selection method optimized for maximum power point is presented and is experimentally validated.

Power management circuit for energy harvesting applications with zero-power charging phase

Energy harvesting systems are becoming an exciting alternative for powering low-power electronics. For applications where real time response is not mandatory, energy harvesting systems can also be used with electronic devices whose power demand exceeds available power. Hence, it operates in two phases: charging and discharging phase. For switching between these two operating phases a power management circuit is used. This paper proposes power management circuit with zero power consumption during charging phase. The proposed design of a power management circuit is evaluated through measurements on a developed prototype. Compared to other power management circuit designs, switching time of the proposed design is up to 30 times faster, debounce-like behavior during switching is eliminated, it supports wider range of output currents and has a lower level-of-complexity.

Impact of propagation medium on link quality for underwater and underground sensors

With the rapid development of wireless networks new application domains are continuously proposed. One of these applications includes an underwater and underground sensor which relies on the properties of diminished RF performance to send the gathered information to a base station. Although many researchers deal with the theoretical background of the channel and propagation models, very few experimental studies regarding the link quality were conducted. Due to the fact that new and more powerful sensor nodes are continuously being developed, the question that arises is how these new and more powerful classes of wireless sensors can handle the harsh environment in underwater and underground networks. Therefore, in this paper the authors analyze the impact of soil, water, moisture and other parameters on the link quality between two sensor nodes in various scenarios. The obtained results present a basis for designing and planning an underground/underwater sensor network.

Impact of capacitor dielectric type on the performance of wireless power transfer system

In loosely coupled wireless power transfer systems, the efficiency is directly affected by the quality factor of the resonant LC tank in both the transmitter and the receiver. This paper studies the impact that the capacitor dielectric type has on the quality factor of the resonant LC tank. Experimental investigation is conducted for low ESR capacitor types and the performance of the wireless power transfer system is evaluated. Focus of the experimental evaluation is placed on the receivers end, i.e. the evaluated parameters are current-voltage characteristics of the receiver and maximum power values. Capacitors are also compared with respect to their ESR values on different frequencies and price. The results show that the capacitor type has a significant impact on the performance of the wireless power transfer system. The correct choice of capacitor type can increase the efficiency of power transfer and the maximum achievable power up to 400 %.

Integrator clamping for asynchronous sigma-delta modulator central frequency increment

Hysteretic comparator (Schmitt trigger) is the basic part of the asynchronous sigma-delta modulator (ASDM). If propagation delay of a hysteretic comparator is not equal to zero and it has measurable value, than it affects the ASDM output frequency spectrum. As ASDM is a circuit with serial connection of an integrator and a hysteretic comparator followed by a negative feedback loop, propagation delay of the comparator will introduce the timing errors in ASDM output signal-triggering events. Therefore ASDM central frequency will be lower then it is in the case for propagation delay equal to zero. This study provides mathematical analysis of the hysteretic comparator propagation delay influence to the ASDM output frequency spectrum. The method for ASDM central frequency improvement using integrator voltage clamping has been proposed. Mathematical analysis, together with simulation and measurement results, shows partial central frequency increment. As ASDM circuit can be used as an oscillator for zero-input signals, central frequency improvement can be significant.