
Use a temperature responsive element such as a thermistor or LM35 module connected to a simple electronic layout that activates an alarm once a preset threshold is reached. A typical build uses a 10k NTC thermistor, a voltage divider with a 10k resistor, and a comparator such as LM358 or LM393. When ambient temperature rises, resistance of the thermistor drops, altering voltage at the comparator input and switching the output state.






