Ljubomir Vracar

Thermal Energy Harvesting Wireless Sensor Node in Aluminum Core PCB Technology

This paper reports the design of a self-powered telemetric wireless sensor node for temperature measurement. The device is realized with a conventional off-the-shelf thermoelectric generator as a power source. It is sandwiched between two aluminum core printed circuit boards (PCBs). One board is exposed to the heat source and has the role of a heat collector, whereas another one with the mounted low profile heatsink acts as a heat spreader. Electronic components of the node are placed on the inner surfaces of the boards. Implemented step-up circuitry is accommodated to achieve stabile cold boot of the node at a low temperature difference between its hot side and ambient (less than 15 °C), even when it is in thermally inefficient position. Operational autonomy of the node in the absence of the heat source is extended by 30% comparing with the common step-up circuitry implementation. The aluminum core PCBs provide node simplicity and compactness, with small overall dimensions.

An Electromechanical Approach to a Printed Circuit Board Design Course

This paper describes a printed circuit board (PCB) design course based on electromechanical workflow. The course relies on the premise that a PCB is an integral component of any electronic apparatus, along with its other electromechanical and mechanical components. To emphasize this to students, electrical and mechanical computer-aided design tools are used in synergy. The course content is described in detail, and the design workflow is illustrated, using a project to design a data acquisition instrument as an example.

Capacitive Pressure Sensing Based Key in PCB Technology for Industrial Applications

This paper reports the design and manufacturing of a device suitable for use in command panels of industrial equipment in the place of mechanical buttons and switches. The device consists of a capacitive pressure sensor, low-cost microcontroller, current driver, and state indication LEDs. All components are embedded into multilayer printed circuit board using standard manufacturing steps. The device has user-programmable properties and it can behave either as a key or as a switch. An interconnection feature is provided in a sense that multiple devices can be organized into an array thus forming a keyboard. A simple two-wire communication interface for controlling the keyboard is described.

The Effect of Flat Panel Reflectors on Photovoltaic Energy Harvesting in Wireless Sensor Nodes Under Low Illumination Levels

This paper discusses the application of flat panel reflectors in conjunction with photovoltaic cell used to power wireless sensor node. The aim of the reflectors is to increase the indoor ambient light energy harvesting efficiency, especially under low illumination levels (<;200 lx). The benefit of the reflectors usage is in the reduction of the node cold boot time and increase of the data transmission frequency. In addition, the physical placement and orientation of nodes in a wireless sensor network is less dependent on the illumination conditions. This paper presents a simple theoretical model suitable for the calculation of the optimal inclination angle for the reflectors. Experimental data show that the cold boot time can be reduced up to 30% and data transmission frequency increased almost twice by using two reflectors of the same size as the photovoltaic cell. The reflectors are produced in the conventional printed circuit board technology, so they can be incorporated into the node design with negligible costs.