The thesis deals with analyses of the laboratory symmetrical supplies with adjustable output voltage. It also describes different kinds of current cut-out circuits and several most frequent supply connection schemes. Analyses (simulation program OrCAD) show the characteristics and behaviour of the mentioned supplies. To set the output voltage, operational amplifier structures or linear three-terminal voltage regulator are very often used. The suggested supply was tested and its parameters compared with the simulations. The value of output voltage and current can be controlled with a computer with a USB port. For controlling of the output voltage and current the digital potentiometers were used and controlled by I2C bus.

Abstract The aims with this report are to document the upgrade and development of new software for the distance laboratory at Blekinge Tekniska Högskola. The work has been focused on implementing the identification number in a microcontroller, to read its data from a so called look-up table and to be able to control digital components through a serial bus (SPI). The look-up table is a list of data from which the software reads data for the different types of printed circuit boards in the hardware component of the distance laboratory is in focus. The results of the report are an implemented, upgraded version of the software and all three aims has been accomplished. Sammanfattning Syftet med detta arbete har varit att utveckla och uppgradera en ny mjukvara till distanslaboaratoriet på Blekinge Tekniska Högskola, genom att implementera adressen till en microcontroller, att läsa dess data från en så kallad look-up table, samt att kunna styra digitala komponenter med en seriell buss (SPI). Fokus i programmeringen har legat på look-up table, vilket är en datalista som mjukvaran läser funktionsdata från för de olika korttyperna i matrisen. Resultatet är en implementerad, uppgraderad version av mjukvaran och alla tre målen har gått att genomföra.

This diploma thesis is focused on complete construction of lab source which is controlled and powered by USB in personal computer. Different types of possible solutions are mentioned and finally one of them has been picked up as a best choice, which is developed in the rest of this thesis. Besides hardware construction there is also shown creation of main program for PIC18F14K50 microcontroller and main application that provides controlling of USB source via personal computer.

The aim of this work is to design a filter of the type low–pass of order 5th with Butterworth’s approximation in the range of over-tuning 10 – 100 kHz and if it will be possible so! achieve even higher marginal frequencies. To compare two typical representatives of the frequency filters cascading and non-cascading synthesis from the viewpoint the accuracy of an! approximation function, sensitivity to the tolerance values of components, number of the components (mainly OZ) and viability, especially the possibility of electronic over-tuning in selected frequency range. On the basis of these conditions will be chosen one design, which will be realized later. Further it will be necessary to consider the possibilities of electronic over-tuning and to choose for this over-tuning suitable component, to design user management changes of marginal frequency fm by the help of keyboard + LCD and control application on the PC. For this hardware will be programmed appropriate control software. At the end of this work will be constructed appropriate device, which fullfils requirements written above and will be subjected to the laboratory measurements that verify function of this device. The constructional details of the filter are presented in the enclosure at the end of this work. At the CD are available all materials, which were created during the master’s thesis or which are necessarily concerned.