Marko Jankovec

Optimal I-V Curve Scan Time of Solar Cells and Modules in Light of Irradiance Level

High-efficiency solar cells and modules exhibit strong capacitive character resulting in limited speed of transient responses. A too fast I-V curve measurement can thus introduce a significant error due to its internal capacitances. This paper analyses the I-V curve error of a measured solar cell or module in light of scan time and irradiance level. It rests on a two-diode solar cell model extended by two bias-dependent capacitances, modelling the junction, and the diffusion capacitance. A method for determination of all extended model parameters from a quasistatic I-V curve and open-circuit voltage decay measurement is presented and validated. Applicability of the extended model and the developed parameter extraction method to PV modules is demonstrated and confirmed. SPICE simulations of the extended model are used to obtain the I-V curve error versus scan time dependence and the I-V curve hysteresis. Determination of the optimal scan time is addressed, and finally the influence of the irradiance level on the I-V curve scan time and error is revealed. The method is applied but is not limited to three different wafer-based silicon solar cell types.

Analog circuit development system

An analog circuit development system as a support in analog circuits design procedure is described. Analog circuit can be designed on a personal computer, uploaded to the board via a USB interface and immediately evaluated. The development board is based on Anadigm AN10E40 Field Programmable Analog Array (FPAA), which is controlled by a MC68HC908GP32 microcontroller, connected to the USB interface. The board features 4 analog inputs, 4 outputs and 5 selectable input/output lines. The whole system is powered from personal computer over USB 5V power lines by means of a DC-DC converter, so that it does not require any additional power supply. Analog circuit design is supported by Anadigm Designer software which also features time domain simulation and filter design tools.

Intercomparison of Temperature Sensors for Outdoor Monitoring of Photovoltaic Modules

Solar cells’ temperature is a very important parameter that affects performance of photo-voltaic (PV) modules since main electrical parameters of PV cells and modules are tem-perature dependent regardless the technology. The present study evaluates and comparesdifferent sensor types and mountings for long term outdoor temperature monitoring ofPV modules along with a standardized method for determination of cell’s temperaturefrom open-circuit voltage. For that purpose, a special multicrystalline silicon PV modulewith miniature in situ Pt1000 temperature sensors was used for reference temperaturemeasurement. On the back side of the PV module different temperature sensors wereattached, including thermocouple (TC), platinum Pt1000 (PT) and digital temperaturesensors DS18B20 (DS). All sensors except one were covered by a 1cm thick insulationblock. The whole setup was mounted on the outdoor PV testing site and all temperatureswere monitored for several days with selection of different environmental conditions. Onthe basis of measurement results, deviations of different temperature sensors are investi-gated and compared to temperature calculated from open-circuit voltage measurementaccording to standard EN 60904-5. Among sensors attached at the back side, covered PTand TC sensors deliver the best results in range of 1–2 C of lower temperature in aver-age; while the covered DS sensor gives additional 1–2 C underestimated temperaturevalues. The worst measurement results demonstrate the PT sensor without insulation. Alltemperature sensors exhibit similar and adequate time response regarding the thermalcapacitance of the PV module. DS sensors, although showing somewhat worse results,offer great advantages if several temperatures have to be acquired simultaneously andrequire very simple data acquisition equipment. They feature comparable measurementaccuracy than commonly used Pt1000 temperature sensors if they are covered by insula-tion with 10mm thick walls in lateral direction to avoid micro-environmental changes.[DOI: 10.1115/1.4023518]Keywords: photovoltaics, measurement

Feasibility Study of Attitude Determination for All-Rotating Unmanned Aerial Vehicles in Steady Flight

All-rotating unmanned aerial vehicles (UAVs) are an interesting subgroup of unmanned aerial vehicles because of their excellent aerodynamics and simple construction. The flight control principle of these vehicles is similar to that of the helicopters. However, due to the all-rotating nature of these vehicles, their flight control mechanism must rely solely on attitude determination. Since the all-rotating aerial vehicles spin at very high angular velocities, the problem of attitude determination requires special attention. This paper deals with the feasibility issues of attitude determination for all-rotating UAVs, based on observations of the gravity and magnetic field vectors. It presents the analysis of magnetometer and accelerometer applicability on board the all-rotating UAV platform, revealing the problematic effects which arise from high spin velocities. The problem of attitude determination is simplified for steady flight, followed by the proposition of a method for eliminating the spin-induced acceleration and a corresponding calibration procedure. Both methods are evaluated in a controlled test environment simulating the steady flight conditions. Test results serve as a proof of concept, making the application of the proposed methods reasonable for future real-flight experimentation and analysis.

Low-frequency noise measurement of optoelectronic devices

A noise measurement setup was designed with emphasis on low frequency noise characterization of optoelectronic devices. Two different low noise amplifiers can be chosen according to desired measurement quantity. By using voltage amplifier SR560, the noise floor of 280nV//spl radic/Hz can be achieved, while for current amplifier an equivalent input current get down to 10fA//spl radic/Hz both at f=100 mHz. The noise spectra can be acquired by a SR780 FFT network signal analyzer in the range from 102.4 KHz down to 244 /spl mu/Hz. The amplifiers feature built in battery power supply, which together with an effective shielding arrangement enables good low frequency interference protection in noisy environments.

FM RDS PnP radio receiver

This paper describes development of a radio receiver that was designed as a personal computer (PC) plug-and-play peripheral device. The radio is capable of receiving FM signals in a standard FM band of 87.5 MHz to 108.0 MHz. Sound output is provided as a line output and a headphones output. All circuits of the radio receiver are controlled using Microchip PIC16F873 microcontroller which communicates with the PC using Universal Serial Bus (USB). RDS data is captured from Microtune 1390EHC tuner and send to the PC where it is decoded and presented to the user. USB also provides power supply to the radio receiver.

Numerical and experimental study of a-Si:H based ultraviolet sensitive detectors

Abstract Thin PIN and NIP ultraviolet detectors are numerically and experimentally studied. The influence of the front contact design on the device performance as well as the transport properties of these thin diodes are investigated. Dark current measurements of PIN and NIP devices with thin I layer (d I nm ) indicate semi-exponential voltage dependent increase at reverse voltages, which can be explained by an electrical model applying a trap-assisted tunneling (TAT) mechanism. The same model explains the low spectral response at longer wavelengths that cannot be simulated using a standard electrical model. Comparison between Ag/PIN and Ag/NIP structure shows worse optical adjustment of Ag/NIP device mainly due to the lower optical gap of N-type a-Si:H layer. Thus, the Ag/PIN device exhibits a better performance than the Ag/NIP device.

Mathematical Model of a Monocopter Based on Unsteady Blade-Element Momentum Theory

This paper presents a simplified nonlinear dynamic mathematical model of a monocopter. A monocopter is an all-rotating unmanned aerial vehicle with a design inspired by a samara, which is the seed from a maple tree. The aim of the model is to describe the essential dynamics of a monocopter in various regimes of flight. The model is based on the unsteady blade-element momentum theory and combines methodologies that are found both in helicopter and wind turbine theories. A qualitative validation of the proposed model shows that the obtained simulation results are in good agreement with the empirical findings and the simulation results of a more advanced monocopter model. The results also agree with the predictions based on helicopter theory and the stability study of a samara seed. The paper demonstrates that simpler methods (such as the unsteady blade-element momentum theory) could be applied to develop efficient and computationally undemanding monocopter models, which are suitable for further research in ...

Analysis of a Single Supply Constant Current Source for Bioimpedance Measurements

Constant current source is one of crucial components of every bioimpedance measurement device. Here we present an analysis of a single supply current source based on a modified Howland circuit. The analysis of track to track capacitances has been performed by finite element numerical device simulation and compared to measurements on developed PCB without soldered elements. Capacitances of the order of 1 pF were simulated/measured the largest being the voltage source to ground capacitance (3 pF). The measured transconductance bandwith was about 3 MHz at 100 Ω load and 100 kHz at 100 kΩ. Circuit analysis with Spice resulted in larger bandwidths compared to the measured ones.

Active Instrument Controller With Script Interpreter

A concept of an active instrument controller with a script interpreter is proposed. It represents a gateway between the computer network and the instrument bus, but, in addition, it can locally execute the measurement script. This introduces distributed code execution in the measurement system, where time-critical measurement loops are locally executed with the main program running on a personal computer (PC). The local execution capability also allows stand-alone operation. We demonstrate the concept with a self-developed active general purpose interface bus (GPIB) controller that uses a CompactFlash (CF) slot. By inserting a communication or a storage card, the controller can operate in network or storage mode. Performance comparison of different operational modes shows a clear advantage of local script execution over conventional network use. Its execution speed is comparable to the commercial script performance implemented in some Keithleys instruments but, in contrast, is applicable to a wide range of different measurement instruments and setups.