Fingerprint recognition car anti-theft system module circuit

Fingerprint identification is a type of biometric identification. It uses the uniqueness and lifelong immutability of fingerprint characteristics to authenticate personal identity, and is extremely safe and easy to use. This article applies fingerprint recognition technology to the car anti-theft system and combines it with the GSM wireless communication network to achieve remote alarm, effectively ensuring the safety of the car.

Working principle: After the car owner stops the car and turns off the engine, the anti-theft device enters the locked state. At this time, if the car key is not in the ON position, fingerprint recognition cannot be performed; only when the car key is in the ON position, fingerprint recognition can be used to unlock the anti-theft device and automatically ignite. In the locked state, the car's oil lines, circuits, etc. are cut off, and the car key cannot ignite; if the connection between the fingerprint collection module and the control box is forcibly cut off, or the car key is forcibly ignited without recognizing the fingerprint, the car will ignite through the horn, Flashing lights and wireless communication network alarm. Insert the password key in the locked state to enter the unlocked state, and perform operations such as fingerprint registration/deletion, mobile phone number setting, and emergency ignition through the keypad according to the LCD and voice prompts.

USB interface circuit

The USB interface circuit is mainly implemented by the file management control chip CH376T. CH376T supports USB device mode and USB host mode, and has built-in basic firmware of the USB communication protocol, firmware of the dedicated communication protocol for handling MassStorage mass storage devices, and communication interface firmware of the SD card. , FAT16, FAT32 and management firmware for FAT12 file systems, supporting commonly used USB storage devices and SD cards. CH376T supports two communication interfaces: SPI interface and asynchronous serial port. This design uses the SPI interface to communicate with the MCU for data, and the circuit connection method is shown in Figure 2. The serial data input SDI, output SDO and clock SCK are connected to SPI1_MOSI of STM32F103VC respectively. SPI1_MISO and SPI1_SCK, the interrupt request output terminal INT is connected to PC0, and the chip select terminal SCS is controlled by PA1. RESET in the figure is the system reset signal, and the crystal oscillator Y1 is selected to be 12 MHz. When the car owner performs fingerprint registration/deletion or emergency ignition, connect the password key (U disk) to J1 to read the password information.

voice circuit

The schematic diagram of the voice circuit is shown in Figure 3. It is composed of the voice chip ISD4004-16 of the American ISD Company and the audio power amplifier LM386 of the National Semiconductor Company. The recording and playback time of ISD4004-16 is 16 minutes (can be segmented). It adopts CMOS technology and operates with a single power supply of 3 V. It contains an oscillator, anti-aliasing filter, smoothing filter, audio amplifier, automatic squelch and high-density multiplexer. The level flashes to store the display. It has built-in microcontroller SPI bus serial communication interface. Analog voice data can be written directly to a single memory unit without A/D or D/A conversion. The ISD voice circuit has many advantages such as natural sound quality, easy use, single-chip storage, repeated recording and playback, low power consumption, and resistance to power outages. LM386 has a wide operating voltage range and adjustable voltage gain. It has the characteristics of low power consumption, wide range of voltage gain adjustable power supply voltage, few external components and low total harmonic distortion. In this design, STM32F103VC transmits voice information to ISD4004 through SPI2. V1 and V2 in Figure 3 are connected to the +3.3 V and +12 V power supplies respectively through transistors. The on and off of the transistors are controlled by PCI1 and PCI2 of STM32F103VC. Only when voice prompts are needed, the transistors are turned on to supply power to ISD4004 and LM386. .