With the development of social technology, people's safety awareness is constantly improving. In modern residential areas or public places, the establishment of various safety devices is very important. Smoke detectors and emergency lighting are two common safety devices among people. Smoke detectors are generally composed of smoke sensors and smoke detection chips. Emergency lighting usually consists of a set of charging and discharging circuits connected to the indoor power supply. Inside buildings, they all require separate wiring, which wastes resources and affects aesthetics. If there is a product that can achieve both emergency lighting function and smoke sensing alarm, then the problem will be easily solved.

System design: As the main functions of the system are emergency lighting and smoke alarm, it can be divided into several main parts for separate design. The following is the system composition diagram. Using MSP430 microcontroller as the core control unit of the entire circuit, it controls other modules to complete various operations. The power circuit adopts an integrated three terminal voltage regulator, which not only needs to charge the battery, but also meets the normal operation of the system. Many modules of the system are easily mature application examples, which will not be repeated here. The following focuses on the design of several important modules.

This article selects MSP430 microcontroller as the core component for the central processing unit. The MSP430 series microcontroller is a 16 bit ultra-low power hybrid digital signal processor launched by TI. It integrates many analog circuits, digital circuits, and microprocessors into one chip for practical application needs. MSP430 is a 16 bit microcontroller based on the Reduced Instruction Set (RISC) architecture. When using an 8MHz crystal oscillator, the instruction speed can reach 8MIPS. The power supply of the MSP430 microcontroller uses a low voltage of 1.8-3.6V, and the power consumption under RAM data retention mode is only 0.1 μ A. The leakage current of the I/O input port is only 50nA. MSP430 has normal operating mode (AM) and 5 low-power operating modes (LPM0~LPM4). When the power supply voltage is 3V, the working currents of various modes are AM: 340 μ A, LPM0: 70 μ A, LPM2: 17 μ A, LPM3: 2 μ A, LPM4: 0.1 μ A. The microcontroller can easily switch between various working modes.

The ultra-low power consumption of MSP430 makes it exhibit excellent characteristics in applications that require very strict power supply, such as alarm systems and portable devices. The MSP430 series microcontrollers combine TI's high-performance analog technology, and each member integrates a wide range of on-chip and off chip peripherals (depending on the model), including multi-channel high-precision ADCs and DACs, on-chip analog comparators, multiple timers with PWM functions, on-chip USART, hardware multipliers, LCD drivers, watchdog timers (WDT), on-chip digital controlled oscillators (DCO), a large number of I/O ports, and large capacity on-chip memory. A single chip can meet the needs of the vast majority of applications. The high integration of MSP430 allows application personnel to easily design truly single-chip systems without having to spend too much effort on various peripherals.