http://hdl.handle.net/2117/1140 2013-05-24T14:53:41Z http://hdl.handle.net/2117/18861 Title: A design method for active high-CMRR fully-differential circuits Authors: Hornero Ocaña, Gemma; Casas Piedrafita, Óscar; Spinelli, Enrique Mario; Haberman, Marcelo 2013-04-18T10:16:22Z http://hdl.handle.net/2117/13386 Title: Hacia la convergencia de las redes inalámbricas de sensores con IEEE 1451 Authors: Higuera Portilla, Jorge Eduardo; Polo Cantero, José Abstract: El mercado mundial de sensores es muy diverso y se extiende ampliamente, con diversos dispositivos que incluyen la detección de variables mecánicas, eléctricas, térmicas, magnéticas, químicas y radiantes. Los avances en sistemas microelectromecánicos (MEMS) han permitido desarrollar sensores embebidos con capacidades de procesamiento y comunicación que reemplazan a los sensores analógicos tradicionales reduciendo los costos de fabricación y con tendencia hacia el desarrollo totalmente digital. 2011-09-29T08:26:06Z http://hdl.handle.net/2117/13324 Title: IEEE 1451 standard in 6LoWPAN sensor networks using a compact physical-layer transducer electronic datasheet Authors: Higuera Portilla, Jorge Eduardo; Polo Cantero, José Abstract: The adoption of the Internet Protocol version 6 (IPv6) networking in IEEE 802.15.4 sensor networks, using IEEE 1451 standardization, increases the interoperability of low-power smart-sensor devices over IP networks. This paper explains the design and implementation of the IPv6 sensor network over low-power wireless personal-area networks (6LoWPANs), and it uses the IEEE 1451 standard in IEEE 802.15.4 sensor networks. We propose the design of the 6LoWPAN physical-layer transducer electronic datasheet (PHY-TEDS) using data-type redefinition with the header compression. Each TEDS was analyzed in terms of memory size, obtaining a reduction of 48% in the PHY-TEDS and 25% in themeta-TEDS with respect to the standard definition. Finally, the IEEE 1451 commands are encapsulated in User Datagram Protocol datagrams to establish communication from the network capable application processor to the wireless transducer interface module in an environmental monitoring application. 2011-09-26T09:58:33Z http://hdl.handle.net/2117/12860 Title: Sensorica: el mundo de los sensores Authors: Pallàs Areny, Ramon; Casas Piedrafita, Óscar; Polo Cantero, José 2011-07-04T09:19:09Z http://hdl.handle.net/2117/12859 Title: Sensorica: el mundo de los sensores y sus interfaces Authors: Pallàs Areny, Ramon; Casas Piedrafita, Óscar; Polo Cantero, José 2011-07-04T09:15:46Z http://hdl.handle.net/2117/12857 Title: Sensórica: el mundo de los sensores y sus interfaces Authors: Casas Piedrafita, Óscar; Pallàs Areny, Ramon; Polo Cantero, José 2011-07-04T09:11:59Z http://hdl.handle.net/2117/12856 Title: Sensórica: el mundo de los sensores y sus interfaces Authors: Pallàs Areny, Ramon; Casas Piedrafita, Óscar; Polo Cantero, José 2011-07-04T09:06:35Z http://hdl.handle.net/2117/12597 Title: Thermal energy harvesting through pyroelectricity Authors: Cuadras Tomàs, Àngel; Gasulla Forner, Manuel; Ferrari, Vittorio Abstract: Pyroelectric cells based on fabricated screen-printed PZT and commercial PVDF films are proposed as thermal energy harvesting sources in order to supply low-power autonomous sensors. The cells are electrically modelled as a current source in parallel with output impedance. Heating and cooling temperature fluctuations generated by air currents were applied to the pyroelectric converters. The generated currents and charges were respectively in the order of 10−7 A and 10−5 C for temperature fluctuations from 300K to 360K in a time period of the order of 100 s, which agrees with the theoretical model. Parallel association of cells increased the generated current. The dependence of the generated current on relevant technological parameters has been also characterized. Finally, current from cyclic temperature fluctuations was rectified and stored in a 1 F load capacitor. Energies up to 0.5 mJ have been achieved, enough to power typical autonomous sensor nodes during a measurement and transmission cycle. 2011-05-18T10:57:24Z http://hdl.handle.net/2117/10973 Title: Runtime extension of low-power wireless sensor nodes using hybrid-storage units Authors: Penella López, María Teresa; Gasulla Forner, Manuel Abstract: The sensor nodes of wireless sensor networks remain inactive most of the time to achieve longer runtimes. Power is mainly provided by batteries, which are either primary or secondary. Because of its internal impedance, a significant voltage drop can appear across the battery terminals at the activation time of the node, thus preventing the extraction of all the energy from the battery. Additionally, internal losses can also be significant. Consequently, the runtime is reduced. The addition of a supercapacitor in parallel with the battery, thus forming a hybrid-storage device, has been proposed under pulsed loads to increase the power capabilities and reduce both the voltage drop and the internal losses at the battery. However, this strategy has not yet thoroughly been analyzed and tested in low-power wireless sensor nodes. This paper presents a comprehensive theoretical analysis that extends previous works found in the literature and provides design guidelines for choosing the appropriate supercapacitor. The analysis is supported by extensive experimental results. Two low-capacity (< 200 mAh) batteries were tested together with their hybrid-storage unit counterparts when using an electronic load as a pulsed current sink. The hybrid-storage units always achieved a higher runtime. One of the batteries was also tested using a sensor node. The runtime extension was 16% and 33% when connecting the hybrid-storage unit directly and through a dc–dc switching regulator to the sensor node, respectively. 2011-01-12T09:29:51Z http://hdl.handle.net/2117/10122 Title: A new MPPT method for low-power solar energy harvesting Authors: López Lapeña, Oscar; Penella López, María Teresa; Gasulla Forner, Manuel Abstract: This paper describes a new maximum-power-pointtracking (MPPT) method focused on low-power (< 1 W) photovoltaic (PV) panels. The static and dynamic performance is theoretically analyzed, and design criteria are provided. A prototype was implemented with a 500-mW PV panel, a commercial boost converter, and low-power components for the MPPT controller. Laboratory measurements were performed to assess the effectiveness of the proposed method. Tracking efficiency was higher than 99.6%. The overall efficiency was higher than 92% for a PV panel power higher than 100 mW. This is, in part, feasible due to the low power consumption of the MPPT controller, which was kept lower than 350 μW. The time response of the tracking circuit was tested to be around 1 s. Field measurements showed energy gains higher than 10.3% with respect to a direct-coupled solution for an ambient temperature of 26 ◦C. Higher gains are expected for lower temperatures. 2010-11-04T16:34:51Z http://hdl.handle.net/2117/8072 Title: On the stability of shield-driver circuits Authors: Spinelli, Enrique M.; Reverter Cubarsí, Ferran 2010-07-08T10:36:47Z http://hdl.handle.net/2117/1396 Title: Thermal noise in a finite bandwidth Authors: Vargas Drechsler, Manuel; Pallàs Areny, Ramon Abstract: In a practical circuit, the output noise due to the thermal noise of a resistor will depend on the actual transfer function of the noise source. The bandwidth will never be infinite because the transfer function of either the noise source or the device measuring the output noise will cause limitations. Consequently, the thermal noise voltage of a resistor in a finite bandwidth is maximum for a given resistor value. That maximum thermal noise voltage depends on the stop frequencies and decreases for both smaller and larger resistor values. 2007-12-03T11:59:38Z http://hdl.handle.net/2117/1395 Title: A novel robust index to assess beat-to-beat variability in heart rate time-series analysis Authors: García González, Miguel Ángel; Pallàs Areny, Ramon Abstract: A new index is proposed to estimate the variance of the differentiated heart rate (RR) time series from its truncated histogram. The index is more robust to artifacts than the standard deviation of the differentiated RR time series (rMSDD) and, unlike the pNN50, does not saturate for very high or very low heart rate variability. 2007-12-03T11:30:15Z http://hdl.handle.net/2117/1393 Title: Error analysis and reduction for a simple sensor-microcontroller interface Authors: Custodio Ruiz, Ángel; Pallàs Areny, Ramon; Bragós Bardia, Ramon Abstract: Error analysis of a resistive sensor-to-microcontroller interface based on pulse-width modulation and time–ratio measurement shows that internal input and output resistances in microcontroller digital ports produce zero, gain and nonlinearity errors. The time–ratio measurement technique cancels these errors when the sensor resistance equals the reference resistor and reduces errors around that point. We propose two simple methods of reducing those errors for sensors with a wide dynamic range. Both methods use time–ratio measurements. The first method uses several reference resistors covering the sensor resistance range; the second method uses two-point calibration. The second method is more efficient and yields errors that can be smaller than 0.5 Ω for a sensor resistance from about 600 Ω to 3550 Ω. 2007-11-30T08:38:35Z http://hdl.handle.net/2117/1392 Title: Compensation of impedance meters when using an external front-end amplifier Authors: Torrents Dolz, Josep M.; Pallàs Areny, Ramon Abstract: Four-terminal impedance meters based on pseudo-bridges yield unexpected uncertainties when using high-contact-impedance electrodes. Adding a front-end amplifier to the impedance meter and rearranging the connection of the meter terminals overcome the contact impedance problem. However, because the compensation provisions in the instrument are meant to compensate only impedance residuals of test fixtures, by either an open/short or an open/short/load correction procedure, the external front-end increases the inaccuracy of the measurement setup. This paper shows that an open/short/load correction can also compensate complicated impedance residuals such as those from external amplifiers. The paper details the correction procedure and provides the equations to calculate the impedance under test from the readings of the impedance meter. 2007-11-30T08:15:27Z