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In this paper, we present a family of fluxgate magnetic sensors on printed circuit boards (PCBs), suitable for an electronic compass. This fabrication process is simple and inexpensive and uses commercially available thin ferromagnetic materials. We developed and analyzed the prototype sensors with software tools based on the finite-element method. We developed both single- and double-axis planar fluxgate magnetic sensors as well as front-end circuitry based on second-harmonic detection. Two amorphous magnetic materials, Vitrovac 6025X (25 [micro]m thick) and Vitrovac 6025Z (20 [micro]m thick), were used as the ferromagnetic core. We found that the same structures can be made with Metglas ferromagnetic core. The double-axis fluxgate magnetic sensor has a sensitivity of about 1.25 mV/[micro]T with a linearity error of 1.5% full scale, which is suitable for detecting Earth's magnetic field ([+ or -]60 [micro]T full-scale) in an electronic compass. Index Terms--Amorphous magnetic material, electronic compass, magnetic sensor, planar fluxgate sensor.

This paper presents a complete autonomous power supply generation system which can find application in a wireless sensor network. Every part of the system is powered only by the energy harvested by an electromagnetic transducer. Besides the transducer, the system comprehends an integrated electronic interface working as step-up ac/dc converter, a high-efficiency step-down dc/dc voltage regulator, and, finally, a load which closely replicates the characteristics of the Analog Devices ADF7242 2.4-GHz low-power transceiver, Texas Instruments MSP430 16-bit microcontroller, and Analog Devices AD7814 temperature sensor with 10-bit digital output. The core of the autonomous power supply system is the transducer's dedicated electronic interface which is designed for transferring the harvested energy to a storage capacitor and is able to process every voltage pulse coming from the transducer, providing the supply voltage for itself and the rest of the circuitry. The system will be analyzed and experimental results demonstrating the possibility of supporting a wireless communication with the harvested energy will be presented for two situations: in the first one the transducer is driven at its mechanical resonance frequency, and in the second one the same transducer is activated through the body movements of a person. [ABSTRACT FROM PUBLISHER]

This paper presents a self-powered, active electronic interface for an energy harvesting system including a vibration-based electromagnetic transducer. The transducer provides a peak voltage of 3.25 V when operated close to its mechanical resonance frequency (about 10.4 Hz) and the power converter has been designed to transfer the harvested energy to a storage capacitor. The circuit is a full-cycle inductive step-up ac/dc converter able to process every voltage pulse coming from the transducer; furthermore, it is supplied by the harvested energy, making the system fully autonomous. The interface has been designed exploiting an accurate model of the transducer in simulations. A printed circuit board version of the interface has been simulated and built to gather experimental results and validate the idea. The system demonstrated to be able to build a voltage across the storage capacitor, which is limited only by the safe operating area of the devices. [ABSTRACT FROM AUTHOR]

We present a photovoltaic energy harvester, realized in 0.35-μm CMOS technology. The proposed system collects light energy from the environment, by means of 2-mm2 on-chip integrated microsolar cells, and accumulates it in an external capacitor. While the capacitor is charging, the load is disconnected. When the energy in the external capacitor is enough to operate the load for a predefined time slot, the load is connected to the capacitor by a power management circuit. The choice of the value of the capacitance determines the operating time slot for the load. The proposed solution is suitable for discrete-time-regime applications, such as sensor network nodes, or, in general, systems that require power supply periodically for short time slots. The power management circuit includes a charge pump, a comparator, a level shifter, and a linear voltage regulator. The whole system has been extensively simulated, integrated, and experimentally characterized. [ABSTRACT FROM AUTHOR]

The paper considers the readout and analogue-to-digital conversion circuitry of the output signals coming from sensors, especially MEMS sensors. The study focuses on the effects that take place when the supply voltage is used as reference voltage for the system instead of the usual reference voltage produced by a band-gap circuit (sigma-delta modulator ratiometric with respect to the power supply). This replacement allows us to save the power dissipated by the band-gap circuit and by the reference buffers, thus optimising the power consumption of the system. The presented results show which are the effects on the converter resolution when its reference voltage is not stabilised. [ABSTRACT FROM AUTHOR]

A high-sensitivity vector two-dimensional (2-D) magnetic sensor system for low magnetic field measurements has been realized and tested. The system, made in PCB technology, consists of a double-axis Fluxgate magnetic sensor and the readout electronic circuitry, based on second-harmonic detection. The amorphous magnetic materials Vitrovac 6025X (25 μm thick) and Vitrovac 6025Z (20 μm thick) were used as the ferromagnetic core of the sensor. By applying a sinusoidal excitation current having a 450-mA peak at 10 kHz with Vitrovac 6025Z, the measured magnetic sensitivity was about 1.25 mV/μT. This value seems to be adequate for the Earth's magnetic field detection (±60 μT). The full-scale linearity error was about 1.5%. By using the thicker Vitrovac 6025X and a sinusoidal excitation current having a 600-mA peak at 10 kHz, a maximum sensitivity of approximately 1.68 mV/μT with a linearity error of about 1.55% full scale in the range of ±60 μT were measured. Due to the use of commercially available ferromagnetic materials, the vector 2-D magnetic sensor system presented is characterized by a very simple fabrication process, thus allowing low-cost devices to be designed. [ABSTRACT FROM PUBLISHER]

The paper presents a switching power system as an alternative to linear power systems driving voice coil motors (VCM) in hard disk drives (HDD). The system is made up of a switching power stage and a suitable modulator. The power stage uses the zero voltage transition technique to control the output voltage slope. The modulator uses the sigma-delta technique and controls the VCM current through a single-loop architecture. Although the structure of the system makes it general purpose, the authors of the paper chose a VCM for HDDs as a target application to test the system. This application is particularly challenging because it requires high-precision current regulation and is particularly sensitive to disturbance and noise. All the significant aspects of the system are then described and discussed. Results derived from the application of the proposed system to a real HDD are presented. The results demonstrate that the output-voltage slope is a parameter fundamental to avoiding interference between the output stage and the channel circuitry and for which an upper limit does exist. Nevertheless, it is high enough to make a switching drive worth considering. In particular, the relationship between the output-voltage slope, HDD performance, current-sensing properties and power-stage efficiency was analysed. The system was designed to be fully integrated. [ABSTRACT FROM AUTHOR]