F.J. Ferrero

A Discharge Lamp Model Based on Lamp Dynamic Conductance

A model for discharge lamp based on lamp electrical conductance is proposed. Physical assumptions are used to obtain this model. The model allows simulating lamp behavior at different frequencies and delivered power levels. The model has been verified using a high pressure sodium lamp supplied at 50 and 100kHz

Measurement of low oxygen concentrations by phosphorescence lifetime using optical fibers

In this paper, a relatively simple, low-cost industrial prototype for measuring low oxygen concentrations in gaseous medium based on phosphorescence lifetime of Al-Ferron in sol-gel probe is presented. The main advantages over other techniques are an excellent sensitivity, precision, selectivity, response time, and facility of maintenance. Fiber optics is used to guide the light. This fact allows one to reach difficult places and to make the measurements from a distance. The design of the system and best ways to maximize the emission maximizing the excitation light from the light source, the optimal distance from the optical fibers to the chemical sensor, and a simple method to filter the response are discussed and verified with the prototype developed. The system allows the detection of oxygen concentrations of 0.005%.

An Acoustic Resonance Band Detection Workbench for HID Lamps

This paper describes an automatic computer-controlled acoustic resonance detection workbench for high-intensity-discharge (HID) lamps. The detection method is based on optical measurements of the discharge arc path. With the aid of a dual lens projection system, relative light intensity measurements at different points of the arc are guided by fiber optic to a photodiode array. These measurements are statistically analyzed to identify when acoustic resonance occurs. Experimental results confirm this method to be a valuable tool to automatically obtain an acoustic-resonance-frequency map for HID lamps.

Design of a Low-Cost Portable Potentiostat for Amperometric Biosensors

This work shows the design of a low-cost, portable instrument for amperometric biosensors, which measures the faradaic currents originated by the electronic interchanges between a specific substance and a biological recognition system, present on an electrode and kept at an appropriate potential. The final objective is to obtain a direct relationship between those currents and the concentration of the substrate to be analyzed. This instrument may be used for sensors or cells with two or three electrodes in order to detect extremely low concentrations of a wide variety of substances. The instrument was evaluated comparing calibration curves from glucose, ethanol and cholesterol biosensors to those obtained from very expensive commercial equipment. Good linearity and sensibility, as well as low noise measurements were obtained. Moreover, thanks to its reduced size and low cost, this instrument can be used directly in field applications

A PSpice model for HPS lamps operated at high frequency

A PSpice circuit model has been developed for the electrical characteristics of high-pressure sodium lamps (HPS). The model is constructed from a two-parameter equation, which is based on a set of two measurements. This model is easily constructed and it is suitable for a preliminary design of electronic ballast. Simulated and experimental results are used to verify the analytical discussions, and an electronic ballast design using the proposed model is presented to further demonstrate its application.

Accurate detection algorithm of battery full-capacity under fast-charge

The expanding number of battery portable products has widely increase the use of sealed NiCd/NiMH batteries. Battery fast-charge (in less than one hour) is very useful but, in fast-charge, cell pressure and temperature increase quickly during overcharging (after the battery reaches full-charge). Usual fast-charge end methods do not avoid the overcharge or they require complex calculation processes. In this paper, a new fast-charge end method is proposed. This method is based on a simple and easily implemented algorithm and it allows us to know accurately and reliably the moment when the battery reaches full-capacity. In this way, a safe fast-charge without negative effects on the effective capacity of the battery and on battery cycle-life is guaranteed.

An equivalent conductance model for high intensity discharge lamps

This paper proposes a model for HID lamps based on equivalent conductance. Model equations have been solved at low and high frequency using a PSPICE. Model results show fairly agreement with experimental data.

The influence of surface coating on the properties of water-soluble CdSe and CdSe/ZnS quantum dots

It is well-known that ligands coating the surface of luminescent semiconductor nanocrystals (quantum dots [QDs]) play an important role in the preparation, stability and physical properties of the colloidal QDs in both organic and aqueous media. Here we report on the synthesis and characterization of core (CdSe QDs) and core–shell structured QDs (CdSe/ZnS QDs), both of them stabilized in aqueous medium through different mechanisms of modification of their surface chemistry. The approaches evaluated for QDs transfer to aqueous media were ligand exchange and polymer coating. Experiments were performed using two typical thioalkyl acids as ligands, namely mercaptoacetic acid (QDs-MAA) and 2-mercaptoethanesulphonic acid (QDs-MES), and an amphiphilic polymer (PQDs) based on poly(maleic anhydride) functional groups. The effects of pH (buffer solution), illumination and the presence of ions in the QD environment on the spectroscopic properties of the different synthesized QDs are reported. The stability of the prepared QDs has been comparatively evaluated aimed to elucidate which surface chemistry provides the suitable properties to be employed as fluorescence labels in distinct types of applications. The experimental results and conclusions will be useful for the development of sensitive sensors or assays adopting QDs as fluorescence labels.

Low-cost system based on electro-oculography for communication of disabled people

This paper describes a new low-cost real-time communication assistive system for disabled people, especially those with only eye-motor coordination. The retinal resting potential causes an electric field around the eyeball, centred on the optical axis, which can be measured by placing electrodes near to the eye. An acquisition system was implemented for measuring this potential in order to detect the movement of the eyes and to provide a relative gaze position, making it possible to codify ocular actions as commands. A human-computer interface (HCI) to control the mouse and a virtual screen keyboard, that offers simple setup combined with high performance, have also been developed. This device has multiple applications, especially in assistive research, where control is governed by means of the ocular position (eye displacement in its orbit). The theory behind the device and the hardware and software design of the system are presented.

Comparison between Different Discharge Lamp Models Based on Lamp Dynamic Conductance

Discharge lamp models based on dynamic lamp conductance are derived from physical equations that describe lamp behaviour. Lamp constructive data are not necessary to build the models, just lamp current and voltage data are necessary. In addition, these models have a relatively low complexity and not much calculation time is necessary to obtain them. They can be used to simulate low and high pressure lamps at low and high (20 kHz < f < 1 MHz) frequencies. Two of these models, derived from different physical equations, are tested and compared using fluorescent and HPS Na lamps.