Real-time demonstration of the main char. of chaos in the motion of a real double pendulum 1 Abst... more Real-time demonstration of the main char. of chaos in the motion of a real double pendulum 1 Abstract. Several studies came to the conclusion that chaotic phenomena are worth including in high school and undergraduate education. The double pendulum is one of the simplest systems which are chaotic, therefore, the numerical simulations and theoretical studies of it have been given large publicity, and thanks to its spectacular motion, it has become one of the most famous demonstration tools of chaos, either through simulations or in real experiments. Although several attempts have been made to use the experiment in laboratory exercises, as the friction in the real experiment changes the nature of the motion and the values of characteristic parameters during the motion, examining the measured (dissipative) motion and to compare with theoretical results raise several questions. In our review, we are presenting a measurement system which is able to analyse these questions. The system, which consists of simple yet precise data acquisition electronics, easily attainable sensors, a Bluetooth module (to the communication with the PC), and an open-source software, demonstrates on-line the main characteristics of chaos and the methods of its study and allows to analyse the dissipative motion. Further information (including downloadable software) is provided on a dedicated page, http://www.inf.u-szeged.hu/noise/Research/DoublePendulum/.
Recently, we have reported on a compact microcontroller-based unit developed to accurately synchr... more Recently, we have reported on a compact microcontroller-based unit developed to accurately synchronize excimer laser pulses (Mingesz et al. 2012 Fluct. Noise Lett. 11, 1240007 (doi:10.1142/S021947751240007X)). We have shown that dithering based on random jitter noise plus pseudorandom numbers can be used in the digital control system to radically reduce the long-term drift of the laser pulse from the trigger and to improve the accuracy of the synchronization. In this update paper, we present our new experimental results obtained by the use of the delay-controller unit to tune the timing of a KrF excimer laser as an addition to our previous numerical simulation results. The hardware was interfaced to the laser using optical signal paths in order to reduce sensitivity to electromagnetic interference and the control algorithm tested by simulations was applied in the experiments. We have found that the system is able to reduce the delay uncertainty very close to the theoretical limit and performs well in real applications. The simple, compact and flexible system is universal enough to also be used in various multidisciplinary applications.
Photogates are probably the most commonly used electronic instruments to aid experiments in the f... more Photogates are probably the most commonly used electronic instruments to aid experiments in the field of mechanics. Although they are offered by many manufacturers, they can be too expensive to be widely used in all classrooms, in multiple experiments or even at a home experimentation. Today all computers have a sound card – an interface for analogue signals. It is possible to make very simple yet highly accurate photogates for cents, while much more sophisticated solutions are also available at a still very low cost. In our review we show several experimentally tested ways of implementing sound card photogates in detail, and we also provide a full-featured, free, open-source photogate software as a much more efficient experimentation tool than the usually used sound recording programs. Further information is provided in a dedicated page, www.noise.physx.u-szeged.hu/edudev.
Recently we have shown a system developed to precisely control the laser pulse timing of excimer ... more Recently we have shown a system developed to precisely control the laser pulse timing of excimer lasers [1]. The electronic circuit based on an embedded microcontroller and utilized the natural jitter noise of the laser pulse generation to improve the long term regulation of the delay of the laser related to an external trigger pulse. Based on our results we have developed an improved system that uses additional, programmable time delay units to tune the noise source to further enhance performance and allows reduction of complexity in the same time. A mixed-signal microcontroller generates a randomly dithered delay of the pulse generation moment to enhance the resolution and also runs a dedicated algorithm to optimize regulation. The compact, flexible hardware supports further enhancements ; the signal processing algorithm can be replaced even by in-system reprogramming. Optimized processing and the relaxed hardware requirements may also support low-power operation, wireless communication, therefore the application possibilities may be extended to many other disciplines .
Sound cards, which count as standard equipment in today's computers, can be turned into measureme... more Sound cards, which count as standard equipment in today's computers, can be turned into measurement tools, making experimentation very efficient and cheap. The chief difficulties to overcome are the lack of proper hardware interfacing and processing software. Sound-card experimentation becomes really viable only if we demonstrate how to connect different sensors to the sound card and provide suitable open-source software to support the experiments. In our talk, we shall present a few applications of sound cards in measurements: photogates, stopwatches and an example of temperature measurement and registration. We also provide the software for these applications.
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Papers by János Mellár