Technical field

The technical solution involves a modular demonstrational panel with electronic protection, powered by short circuit resistant power sources of safe low voltage for safe execution of experiments in school classes and educational institutes in the field of physics classes - electrical engineering and electrical chemistry.

Current technical status

Various kits (demonstrational panels) are used to perform experiments in physics classes (electrical engineering and electrical chemistry), demonstrational panels are powered by various systems - battery power sources, local adjustable sources of safe low voltage, central adjustable source of safe low voltage. In the way they are currently being used, these power supply systems pose a threat to health and/or the material parts of demonstrational panels. They also limit the possibilities of experiments - time-wise, as well as limiting the conclusions, and do not enable equal conditions for experiments across all panels.

Demonstrational panels are usually assembled from plastic module elements (boxes), with electrical wiring diagram symbols printed on them. The module elements are put onto a base board. These demonstrational panels allow a variety of possible experiments, but are limited by the number of module elements within the particular kit. Additional module elements need to be purchased for other experiments. Demonstrational panels made of module elements usually have battery or local power supply. If a central power supply is used, there is a danger of module damage. There is an alternate option to the demonstrational panels, so-called suitcase kits, which consist of one large, unmodifiable circuit board rather than individual modules. These only allow a limited number of experiments. Other experiments require another suitcase kit, which presents more possibilities for experimenting. These modules have battery, local power supply; alternatively, they can have a central adjustable power supply. Neither demonstrational panel types have any electrical protection. Batteries are the most common power supply type for the demonstrational panels. It is not possible to control the voltage settings and the battery needs replacement. Experiments with increased current draw can only be performed for short periods of time. There is a risk of burning yourself when using powerful batteries. Electronic pieces may be destroyed and require replacement if an improper connection is made during an experiment. Experiments employing battery power supply are limited by the extent of the voltage of the used batteries. That means it is difficult to perform experiments in higher voltage ranges.

Usage of local independent power sources is a matter of setting this source for each demonstrational panel. The voltage cannot be set centrally from the teacher's switchboard. This usage also poses risks of damaging the demonstrational panel or burning a student if they set a higher voltage value or higher current limitation. While this source, which can be purchased separately for the kit, includes safety sockets, it is not possible to use safety cables as the kit itself is not fitted with safety sockets.

On the other hand, a central adjustable source used to power the demonstrational panels is located at the teacher's workstation and can be used to set the voltage centrally. The teacher's switchboard contains a low-voltage circuit as well as galvanically separated low alternated voltage. This concept usually utilises one source of safely galvanically separated low alternated voltage, comprising of a transformer with socket switching, or up to three sources of safely galvanically separated low alternated voltage with AC/DC output voltage switching. The safely galvanically separated low alternated voltage sockets are in parallel connection and usually placed in the electrical box along with the low voltage sockets. This connection can dangerously influence individual parts of demonstrational panels used by students to perform experiments. A short circuit may occur in case of incorrect connection, resulting in outage at the teacher's workstation or diverting the entire power to a single demonstrational panel. This can result in excessive heating of demonstrational components and burning of students (e.g. when experimenting with resistor wires). This is because the power of the source in the current technical status needs to be a sum of the power values required to all of its demonstrational panels. Additionally, a short circuit can damage demonstrational modules on the demonstrational panels and influence all other workstations, making it impossible to carry on with the current experiment. Distribution of low voltage from the teacher's distribution board to individual demonstrational panels also causes non-negligible voltage loss, which results in varied voltages on individual demonstrational panels. If a student has connected a device with higher power consumption to one demonstrational panel, the voltage loss in the line causes the voltage on other demonstrational panels to be significantly lower. The cable circuit voltage loss ( and therefore voltage on demonstrational panels) is dependent on the distance from the source aaid power consumption of devices connected to individual demonstrational panels. This means that wires with a large cross-section have to be used to distribute the low voltage from the teacher's switchboard to individual demonstrational panels.

Technical solution basis

Tlie new technical solution is comprised of a modular demonstrational panel with electronic protection, powered by short circuit resistant power sources of safe low voltage for safe execution of experiments in classes in the field of physics - electrical engineering and electrical chemistry.

This solution allows central setting of equal voltage for all modular demonstrational panels included in the student workstation system from the teacher's workstation, with limitation of source output power, where the power for modular demonstrational panels can be safely limited by the power of the local source, meaning that a short circuit of one modular demonstrational panel will not influence other modular demonstrational panels. There is also an output voltage setting option. The modular demonstrational panels included in this technical solution consist of individual swappable modules on a circuit board. On the front side, the circuit board is imprinted with its description and corresponding diagram symbol or its wiring and described real element. These swappable modules have electronic protection built into their bottom side. In case of any error during experiments, this protection prevents any damage to the power source, module or module components. The technical solution offers a collection of individual known technical elements, arranged in a technical solution ordered from the top. It forms one invention concept under the specified condition. This technical solution lies in a safe and time- unlimited execution of experiments, which allows equal conditions during experiments at all student workstations, without the limitations to experiment conclusions present in contemporary solutions. Overview of figures

The modular demonstrational panels with electronic protection powered by short circuit resistant power sources of safe low voltage are illustrated by the following figures: Figure 1 - technical concept of the modular demonstrational panels with electronic protection, powered by short circuit resistant power sources of safe low voltage; Figure 2 - modular demonstrational panel; Figure 3 - demonstrational module; Figure 4 - demonstrational module electronic protection

Example of technical implementation

The technical solution is implemented by fitting student workstations 1 , which include modular demonstrational panels 2, with short circuit-resistant sources of safe low voltage 3 powered by adjustable voltage of 0-230 V from an automatic transformer 4 at the teacher's workstation 5. Modular demonstrational panels 2 consist of individual demonstrational modules 6. These demonstrational modules 6 consist of a circuit board 18 fitted with components 7 such as LEDs, safety sockets 8 and a protective circuit 9. The circuit is located at the bottom side of the demonstrational modules 6. In case of incorrect safety socket connection 8, this circuit ensures that the excess power is discharged safely.

The teacher's workstation 10 contains a control switchboard 5 and short circuit-resistant source of low voltage 3. The short circuit source of safe low voltage 3 is conceived by a short circuit resistant separating transformer 12 and generates safe galvanically separated low alternated voltage 11 (between the output terminals 17). The control switchboard 5 at the teacher's workstation 10 is powered via a power supply cable 13 from the public distribution network by low alternated voltage and is fitted with an automatic transformer 4 and an alternated voltage voltmeter 14. The automatic transformer output voltage 4 is connected via cable 15 to the input terminals 16 of all short circuit sources of safe low voltage 3 at the same time; these are also placed at all of the student workstations 1. All short circuit sources of safe low voltage 3 include short circuit-resistant safety separating transformers 12, which are unconditionally resistant to short circuit and of the same type. Secondary transformer voltage is connected to the output sockets 17. Since the included short circuit-resistant safety separating transformers 12 are of the same type, they have the same primary voltage (i.e. automatic transformer output voltage 4) as well as the same secondary voltage (within the transformers' production allowance). The short circuit-resistant source of safe low voltage 3 at the teacher's workstation 10 is identical to the short circuit-resistant sources of safe low voltage 3 at all student workstations 1. The teacher may perform the experiment simultaneously with the students and compare the results. Voltage is set using the automatic transformer 4 and the output voltage value is read from the alternated voltage voltmeter 14. The range of the voltmeter is 250 V AC 50 Hz, but the scale corresponds to the related output voltage of the short circuit-resistant source of safe low voltage 3 at all of the student workstation 1. There can be 1-99 student workstations.

Industrial applicability

The technical solution is applicable for performing experiments at elementary and high schools, as well as other educational institutes, especially in the field of physics - electrical engineering, electrical chemistry - and leisure facilities.