Abstract: In order to prevent electrical fire accidents, a combined electrical fire detector is designed and developed with STM32F103VCT6 as the main controller and NB-IoT as the communication module. The detector collects fault information such as short circuit, open circuit, over-voltage, under voltage, over-current, temperature abnormality and leakage of electric equipment and transmission lines, will immediately send out an audible and visual alarm and display its fault information on the screen, and simultaneously upload the information to the Internet of things platform, push the fault information to the user in time through the computer and mobile phone, and conduct remote supervision on it.The test results show that the electrical fire detector is sensitive,stable and the equipment operates stably.

Key words:  MCU, NB-IoT, electrical fire detector, Internet of things