Circuit Design of Intelligent Alarm System Based on Single Chip Microcomputer

　　The system uses the 16-bit single-chip microcomputer SPCE061A of Lingyang Company as the main controller. The smoke sensor and the human body pyroelectric infrared sensor respectively sense the smoke and human infrared signals, and the single-chip microcomputer makes an alarm action. Two Lingyang single-chip microcomputers are used as slave stations to achieve the purpose of remote network monitoring. The design of dual photoelectric switches is used to sense the entry and exit of personnel. The radio frequency signal transmitting and receiving device is used to sense the entry and exit of valuables. The test results show that the system works well, and the entry and exit of personnel and valuables in a few days are recorded. The main innovation of this design is the use of single-chip microcomputers for control, which can realize network monitoring.

　　Smoke Detection Circuit Module

　　The MQ-2 smoke sensor is used, which has the advantages of wide detection range, high sensitivity, fast response recovery, excellent stability, long life, etc. It can realize smoke detection with a simple driving circuit. The smoke sensor circuit is shown in Figure 2. When no smoke signal is detected, the comparator outputs a low level; when the sensor detects a smoke signal, the comparator outputs a 5V high level and the alarm is activated.

　　Figure 2 Smoke sensor structure diagram

　　Human infrared detection circuit module

　　The passive infrared human body sensor is composed of chip BISS0001, pyroelectric infrared sensor KBS-6B and a few external components. The addition of Fresnel lens greatly increases the detection range and satisfies the human body detection requirements. When someone passes through the pyroelectric sensor, the Vo port of BISS0001 outputs a positive pulse and the alarm is activated. The circuit structure is shown in Figure 3.

　　Figure 3 Structure of pyroelectric infrared sensor

　　Personnel entry and exit detection circuit module

　　Two infrared photoelectric switches placed front and back are used to determine whether a person enters or leaves the dormitory by detecting the switch sequence. When someone leaves the dormitory, control signal 1 is set high first, and then control signal 2 is set high. By judging the timing sequence, it can be concluded that the person has gone out. The same applies when someone enters. The detection circuit is shown in Figure 4.

　　Figure 4 Personnel entry and exit detection circuit diagram

　　 Valuables detection circuit module

　　In order to meet the requirements of valuables detection, a single tuned loop resonant amplifier is placed in the card, the card is hung on the valuables, the card sends out a radio frequency signal, when it enters or leaves the dormitory, it resonates with the secondary coil, the load voltage changes, and the entry and exit of the person can be recorded by detecting the load. The circuit is shown in Figure 5.

　　Figure 5 Valuables detection circuit diagram

　　To realize remote monitoring of dormitory security, a master-two-slave mode is adopted for simulation. The master station can search the slave station, display whether the slave station is online in real time, receive, process, display, record and alarm information, and the slave station acquires and sends information. The master station can display the slave station information in real time, and store the alarm and valuables in and out information in the master station's FLASH, eliminating the need for external storage chips, which can be easily read and displayed. The human body sensor is used to determine the number of people in the dormitory by counting the number of people entering and leaving the dormitory, and the door is locked. The internal clock of the microcontroller is used as the time reference, and the time is set through the keyboard to record the alarm time. The voice module inside the microcontroller is used to realize voice alarm, which is intuitive and practical. This control scheme makes full use of the internal resources of the microcontroller, uses fewer external devices, and is simple and practical.