In this master’s thesis, conducted in collaboration with the Biotechnical Faculty, University of Ljubljana, we developed a bio-logging device for recording audio and movements of wild cats (Felidae). The device must be sufficiently small and lightweight to reduce the negative impact on animals, particularly for smaller species like Eurasian lynx. It also requires enough energy storage and needs to be efficient enough to work independently for at least one year in the field. It is mounted on existing collars, which already have built in GPS tracking of the animal. The collar falls off the animal after a predetermined time and gives off a signal to facilitate retrieval. Consequently, all data are stored locally on the device, eliminating the need for external communication once recording begins.
The greatest challenge is the device’s limited energy supply. Due to space constraints, we were able to use only two 2/3AA batteries, providing just 15.12 Wh of energy. Power consumption was reduced through the use of an STM32U535 microcontroller, optimized for low-power operation. We employed autonomous peripheral units that offload tasks and allow the main core to remain in sleep mode during most operations. A low-loss switching voltage regulator was used for power conversion. The microphone employs sound detection to further reduce consumption, activating recording only when the animal vocalizes.
The final device will be capable of operating for more than one year while occupying only 4 * 4 cm, making it suitable for attachment to all species of wild cats and other animals. In addition, it will support extended functionalities that can prolong operation to over two years.
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