Andrei Drumea

Modelling, simulation and testing of an autonomous embedded system supplied by a photovoltaic panel

The concept of energy harvesting, to produce electrical energy from other existing forms of energy from the environment, has become very popular for a range of low power applications, like wireless sensor networks, data-loggers or identification devices. Solar energy is the best type of energy harvesting in terms of produced power, but has a major drawback - no available energy during the night. A solution to compensate this problem is to store electrical energy in the daytime and to offer it in the night; there are many implementations, involving use of different type of accumulators (lead-acid, NiMH, LiIon) or supercapacitors. Presented paper focuses on modelling and simulation of an autonomous embedded system that uses supercapacitor for energy storage and photovoltaic panel for power generation. Design, implementation and testing of the embedded system are also presented.

Control of industrial systems using Android-based devices

Computer control systems for industrial processes need good processing power and memory resources, standard networking options and enough input/output lines for connecting to sensors, actuators and field buses. The explosive development of mobile devices running Android operating system brought us low cost devices that fulfill almost all these requirements for industrial control, missing only input/output lines. This last aspect was solved with launching of the latest 4.x Android release and of multi-interface Android USB hosts chips. The paper presents some test and results of controlling of an industrial system - hydraulic test bench- with a Google Nexus 7 tablet; hardware and software aspects are analyzed and advantages and disadvantages of this solution compared to PC-based one are discussed.

Designing low cost embedded systems with ethernet connectivity

This paper focuses on hardware and software aspects in development of low cost embedded systems with Ethernet interface for industrial applications like smart sensors and mechatronic control. Ethernet connectivity allows a standard and easy networking method as well as remote Internet access but usually requires higher resources (processing power and memory) than serial connections like RS232/485. Embedded systems based on low cost 16 bit microcontrollers have limited resources so Ethernet access implementation requires careful hardware and software design. Our paper presents a simple solution for implementation of Internet access for simple industrial control systems and smart sensors. Hardware is based on low cost Ethernet controller chips attached to 16 bit low power microcontroller with limited memory resources (0.5…4Kbytes RAM) and software is a simplified, low memory footprint TCP/IP stack implementation that offers Ethernet connectivity in local network. For Internet access, a standard router with enabled VPN (Virtual Private Network) can be attached to local network. Some performance tests and analysis regarding communication speed, RAM memory requirements for microcontroller are presented.

Modelling and simulation of energy harvesting with solar cell

The paper focuses on modelling and simulation of energy consumption of an autonomous embedded system with a solar cell as energy source. Mathematical models for energy consumption/generation for solar cell, microcontroller and its peripherals are elaborated, tested and coupled together for complete system simulations that allow system configuration and optimization for specific cases.

Modelling and simulation of an inductive displacement sensor for mechatronic systems

The paper presents design, simulation, implementation and testing of an inductive displacement sensor based on a Linear Variable Differential Transformer (LVDT) controlled by a single chip electronic module with 16 bit RISC microcontroller. LVDT device is widely used in hydraulic and pneumatic mechatronic systems for measuring physical quantities like displacement, force or pressure; it consists of two magnetic coupled coils with a common moving core; its displacement is converted in reluctance variation of magnetic circuit. Standard electronics for LVDT sensor conditioning is analog - quadrate oscillator, synchronous demodulator and amplifiers - but has its drawbacks – relative complex, hard to adjust, many components and packages, no connection to computer systems. The originality aspects of the work come from the unique method of finding displacement information by switching supply voltage in the coils of inductive device. This method uses only peripherals from a microcontroller so is low cost and easy to adjust. Present paper focuses on modelling and simulation of displacement measuring method but analyzes also implementation aspects for a real application (an electro hydraulic position control system).

GSM solutions for low cost embedded systems for industrial control

Control systems with remote access capabilities become today more and more popular due to their extra advantages - control from distance and possibility to automate (batch processing) different tasks. An off-the-shelf technology for remote access is GSM (Global System for Mobile Communications) and can be easily integrated into embedded systems using modern GSM serial modems. Another trend in control systems is represented by architectures based on system on chip devices - advanced 8 or 16 bit microcontrollers. These paper studies hardware and software aspects - performance, tradeoffs and pitfalls - of GSM communication implementation using low cost system on chip devices like Atmel ATMega128 and Texas Instruments MSP430FJ49

Analysis of current carrying capacity of silver-based conductive pastes for PCB repair

This paper presents some investigations on the current carrying capabilities of PCB traces repaired with silver-based conductive paste. Such PCB traces with different parameters (width, gap and substrate) are tested at different currents and electrical and thermal measurements are performed. An automated measurement system is used for observing any change in trace resistance for the time span of each test.

Modelling and simulation of sensors for position control for hydraulic mechatronic systems

Many electro-hydraulic applications like automated manufacturing tools and systems, robotics or seismic test benches for civil engineering require precise control of hydraulic cylinders. This control can be obtained only using reliable and accurate position sensors, usually resistive or inductive. The paper presents design, modelling, simulation and implementation of two types of position sensors for hydraulic mechatronic systems - differential inductive type and integrated accelerometer-based. Both sensors use microcontrollers for data processing and communication. Each type has its advantages - the inductive sensor is more accurate, accelerometer-based one requires simpler mechanical construction. The idea of using of accelerometer-based sensor was to replace standard displacement transducer attached on the cylinder with an accelerometer connected to a microcontroller that reads acceleration data and calculates displacement, thus eliminating mechanical coupling between cylinder rod and cylinder body. Both solutions are analyzed and compared on the same hydraulic test bench.

Thermal investigations on high power LEDs

The present and near future lighting solutions will include surely power light-emitting diodes (LEDs). With increasingly power offered by the modern structures, thermal management issues can arise. In this paper we present thermal investigations on three type of power LED, of 1W, 3W and a 10W module. The investigations are oriented in direction of offering trusty suggestions and solutions regarding the thermal regime of discrete LED used as stand-alone or in assembly modules. The temperature will be determined through thermal simulation. The simulation based on finite-element models will bring valuable results, especially for multiple LED modules for which the model with thermal resistance offer only global results, without information of PCB temperature. For the measurements preparation the LEDs are attached to printed circuit boards (PCBs): classic FR4 and metal core PCB (MCPCB). The measurements will be done by combining thermocouples data acquisition system with IR thermovision camera.

Universal development board for education in embedded systems

Design and programming of embedded systems require skills that need training and practice. Usually these activities are performed using a development board equipped with a specific microcontroller and a software environment for firmware development. The main problem of such approach is its focus on only one device type - other microcontroller families require other development boards. This aspect becomes important in a university laboratory, where students have to work with different types of embedded systems. For example, in our department of Electronic Technology, three8-bit and one 16-bit microcontroller families are used in different projects. Each microcontroller type requires its own development board with its own set of peripheral devices; this is a waste of resources and so came the idea to use the same set of peripherals on a motherboard and to plug in a daughterboard with a specific microcontroller and its associated circuitry. One motherboard and three daughter boards were designed and tests were performed.