This thesis describes the development of a device for automated start-up testing of electric motors. The device is connected between a laboratory power supply and the motor control electronics under test. It then automatically switches the motor's supply path on and off at user-defined time intervals, measures the motor current to determine whether each start-up attempt was successful, and keeps statistics of the results.
We developed both a printed circuit board and the accompanying software for the device. The motor's supply path is switched by a power relay, which the microcontroller controls through an auxiliary relay and a transistor, while the current is measured with a galvanically isolated sensor based on TMR technology. From the input voltage, two switching regulators generate the 24 V required for relay control and the 3.3 V that powers the microcontroller and the logic section of the circuit. The software, written in C, is designed so that time-critical tasks are executed by a timer interrupt every millisecond, while slower tasks are handled by the main loop. Settings, start counters, and statistics are stored in flash memory. A display and four buttons form a simple user interface through which the user can change settings and monitor the device's operation.
Finally, we assembled and tested the device. Based on the faults we found, we made the necessary corrections and built an improved version, which works as expected and is ready for practical use.
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