Embedded systems with Linux: programming the Beaglebone board

Postprint (published version

Embedded systems with Linux: programming the GPMC driver

Peer ReviewedPostprint (published version

Embedded systems with Linux: working with the TT01 cape

Postprint (published version

Analysis of the dynamics of an active control of the surface potential in metal oxide gas sensors

Postprint (author's final draft

Using a Second Order Sigma-Delta Control to Improve the Performance of Metal-Oxide Gas Sensors

Controls of surface potential have been proposed to accelerate the time response of MOX gas sensors. These controls use temperature modulations and a feedback loop based on first-order sigma-delta modulators to keep constant the surface potential. Changes in the surrounding gases, therefore, must be compensated by average temperature produced by the control loop, which is the new output signal. The purpose of this paper is to present a second order sigma-delta control of the surface potential for gas sensors. With this new control strategy, it is possible to obtain a second order zero of the quantization noise in the output signal. This provides a less noisy control of the surface potential, while at the same time some undesired effects of first order modulators, such as the presence of plateaus, are avoided. Experiments proving these performance improvements are presented using a gas sensor made of tungsten oxide nanowires. Plateau avoidance and second order noise shaping is shown with ethanol measurements.Postprint (author's final draft

Characterization of dielectric charging in MEMS using Diffusive Representation

Postprint (author's final draft

Effect of dielectrophoretic force in the self-assembly process of electrosprayed nanoparticles

In this work the effect of the dielectrophoretic force (DEP) in the self-assembly process of nanoparticles electrosprayed onto a substrate, is examined. DEP force is originated by the electric field created by the electrospray gun and by the distortion of the field created by the effective dipole of each nanoparticle. It is also shown that the modulus of this force is large when the distance between particles is few times its diameter, provided the medium is wet and the electric field is not switched off. The directional nature of DEP In this wet phase, is shown to chain nanoparticles aligned with the main electric field direction. Although there is a repulsive force between chains in the orthogonal direction to the field, it is minimum when the beads align with the voids in the nearby chains. DEP is a dominant force in the close distances of nanoparticles compared to double layer, van der Waals, electrophoretic retardation, weight and buoyancy.Preprin

Circuit modeling of a MEMS varactor including dielectric charging dynamics

Electrical models for MEMS varactors including the effect of dielectric charging dynamics are not available in commercial circuit simulators. In this paper a circuit model using lumped ideal elements available in the Cadence libraries and a basic Verilog-A model, has been implemented. The model has been used to simulate the dielectric charging in function of time and its effects over the MEMS capacitance value.Peer ReviewedPostprint (published version

Pulsed digital oscillators

The objective of this paper is to collect the main latest results on pulsed digital oscillators. Rigorous and experimental results are presented that show what kind of sequences are at their output, the relation between these sequences and those of first-order sigma-delta modulators and how is their performance in practical applications. A new variation of the standard topology of PDOs, on which the feedback variable is not position but the velocity of the resonator, is also presented. The first preliminary results obtained with a PDO working with a MEMS cantilever for chemical sensing are presented, which show that it is possible to infer the oscillation frequency directly from the bitstream at the output of the oscillator. Finally, the dependence of the oscillation frequency as a function of the initial conditions of the resonator are also analyzed with simulations.Peer ReviewedPostprint (published version

Multiphysics simulation of REMS hot-film anemometer under typical martian atmosphere conditions

The purpose of this paper is to describe numerical electro-thermal simulations of the REMS wind sensor unit [3] and the results obtained by using COMSOL multiphysics. This device is a hot-film anemometer for 2D wind measurements, which does not have movable parts and is based on the air stream forced heat convection to the environment. This wind sensor works as a thermo-electrical transducer where the same equilibrium temperature is reached for every value of the wind speed, by means of a power supply modulations. Therefore, thestraightforward relationship between the amount of power delivered to the unit and the wind speed can be derived as earlier presented [2]. Detailed finite element simulations enabled us to predict the temperature distribution, recognize hot and cold spots and characterize besides the thermal profile the operating sensing magnitudes.Postprint (published version