This paper introduces an automatic fire detection and alarm controller controlled by PLC. The smoke detector and the temperature detector are connected to PLC, and judged by PLC logic. The special acousto-optic alarm integrated circuit is used for fire alarm, abnormal alarm (one of smoke detector and temperature detector) and fault alarm, and different acousto-optic signals are sent out to display the accident type and location. The controller is suitable for libraries, archives, computer rooms and other places with a total construction area of less than 1000 om2. Because PLC system has high integration, strong anti-interference, simple programming and convenient development, maintenance and upgrade, it has simple structure, strong reliability, low development, use and maintenance costs and is easy to popularize. Keywords: programmable controller; Automatic fire alarm; Smoke detector; Temperature sensing probe; Automatically monitor the sudden change of indoor smoke and temperature and give an alarm. 2. If the detector is left behind, the wiring is faulty or the internal components are damaged, it can give an audible and visual alarm. 3. If one of the two detectors indicates that there is an abnormal phenomenon in the room (such as excessive smoke concentration or excessive indoor temperature difference), the device can send an abnormal alarm signal so that the personnel on duty can go to the scene to deal with it. 4. If the smoke and temperature detector act at the same time, it indicates that there is a fire, and the device will give a fire alarm. 5, failure, abnormality, fire alarm sound, light is different, there are obvious differences, and can accurately display the accident type and location. 6. Interface is reserved for future system maintenance and upgrade. I. Introduction In recent years, the construction industry has developed rapidly, and modern buildings need fire alarm and even automatic fire control systems. At present, domestic manufacturers still produce products based on transistors, small-scale integrated circuits or single-chip computers, which are complex, costly and difficult to maintain. Therefore, I put forward the idea of an automatic fire alarm controller controlled by PLC, which is simple in structure, moderate in cost and easy to maintain and upgrade. The device can meet the following requirements: 1. The device has a smoke detector and a temperature detector, which can be used to check the system composition and working principle. The hardware principle of the system is shown in figure 1. 1 is a detector, including temperature and smoke to collect various information; 2. PLC controller to realize logical judgment and control; 3 is power supply, which provides 24V DC power supply; 4 alarm display panel, which can accurately display the accident type and location; 5 is an acousto-optic alarm circuit, which sends out three different acousto-optic alarm signals. PLC constantly sends detection signals to the detector, and its feedback signals are collected by PLC to judge whether it is normal, faulty, abnormal or fire, and then control the acousto-optic alarm circuit. 1, detector sensor world 2000.7-27 technology and application technology &; The mechanical differential temperature detector is used for the ~ (1) temperature detector of Xiangyi brand in California, USA. The detector has simple structure and high sensitivity, and is suitable for occasions with small temperature change. It consists of bimetals with different expansion coefficients. When the temperature changes, the two metal strips will bend, thus making the contacts connected. The working principle of temperature sensor signal detection is shown in Figure 2(a). The temperature detector K has three terminals, and L is the detection line to check whether the detector is faulty; 2 is the power cord; 3 is a signal line from which a signal can be sent if the temperature detector operates. Usually, a rectangular wave signal is applied to the detection line, as shown in Figure 2(b), and the high level is the detection period. As can be seen from Figure 2(a), when the 1 terminal is at a high level, the output of the 3-terminal signal line is at a high level, which is normal. On the contrary, if the terminal L is high and the terminal 3 is low, it indicates that the temperature sensor is faulty, so whether the detector is normal or not can be checked according to the level of the signal line at the terminal 3 of the inspection cycle. During the test, there is no voltage at terminal 1. If the temperature sensor does not operate (k is not closed), the signal line 3 should also have no level output. If the temperature sensor operates when the K contact is closed, even if there is no level input at the 1 terminal, the signal line 3 will have a level output, which is the power supply voltage. Therefore, whether the temperature sensor operates or not can be judged according to the voltage at the terminal 3 in the detection period. Therefore, it is judged whether the detector is lost or disconnected and whether the indoor temperature is abnormal according to the output level on the signal line 3 in different time periods of the detection line. Baba County Cascade Tu Tu 1 System Hardware Schematic Diagram Guang Guang Guang Guang 22222222222222222PLCCCCC Alarm Circuit Lulu lllll Detector Device Device Device Device Device Device Device Device Device Device Device Device Device Device Device 1 1 Inspection Line 222 Power Line 333 Signal Line ((a)) The terminals of temperature detectors are connected one by one, (b). (2) The smoke detector adopts ion smoke sensor. Fig. 3(a) is a schematic diagram of an ion smoke sensor, and fig. 3(b) is an operating voltage waveform diagram. It consists of 1 inspection ionization chamber, 2 compensation ionization chamber, 3 signal amplification circuit, 4 switch conversion circuit, 5 fire simulation inspection circuit and 6 fault automatic monitoring circuit. When there is no smoke, the voltage of compensation room and inspection room is almost equal; When there is smoke, the smoke enters the inspection room, which reduces the ionization charge migration speed, ionization current, equivalent impedance of the monitoring room and the impedance in the compensation room, thus causing the change of the partial pressure ratio of the ionization room and generating voltage △V at the input end of the signal amplification circuit. When the voltage increases to a certain value, the switching circuit will act immediately, send out an alarm signal and light the confirmation lamp. In order to prevent circuit disconnection, poor contact and sensor loss between sensor and controller, an automatic fault monitoring circuit is provided. When one of the above situations occurs, the fault monitoring circuit works and sends an alarm signal to prevent the internal components of the detector from being damaged and causing false alarm. The sensor is equipped with a fire simulation check circuit, which is regularly connected to the level, and the signal terminal should have a signal, otherwise the sensor fault should be reported. As can be seen from the working voltage waveform diagram in Figure 3(b), a rectangular voltage waveform is applied to the sensor detection line. If the sensor is normal, the level on the signal line is the same as the waveform of the detection line. If the internal components of the sensor are damaged or disconnected, the signal line voltage has no voltage regardless of the detection line voltage, which is the fault state. When the detection line has no level input, the signal line still has voltage output, indicating that the smoke detector has acted. 2.PLC control system PLC adopts C20 programmable controller of Omron Company of Japan. Its input terminals 0000-00 15 are respectively connected to the smoke and temperature sensing signal lines in each room (at most 16). The output terminal 0500 outputs a rectangular wave signal, which is connected to the smoke temperature inspection circuit of each room, 050 1-0503 is connected to audible and visual alarm to send out different acousto-optic signals, and 050 1-0508 is connected to the alarm display panel to display the accident type and address. 3. Alarm display panel The panel of the alarm display panel is shown in Figure 5. The status signal sent by PLC output terminal 050 1-0505 is sent to the alarm display panel, which can display smoke, abnormal temperature or fault or fire status, and the four-digit address signal sent by 0506-0509 is sent to the display panel, which can display the specific address (up to eight digits). SenSOrWOrjd2D00.7 ~~ dry acoustic cutting technology and its application technology &; Apply for a white dagger, ... span class =' class1' > 7U-A inspection line B power line 6 fault automatic all-inclusive customer confirmation lamp inspection ionization chamber signal amplifier 5 fire simulation inspection circuit 4 fault automatic monitoring circuit 2 compensation ionization chamber C signal line D ground line (a) ion smoke detector principle inspection line one by one-learning signal line (normal) signal line (abnormal) (b) working voltage waveform Figure 3 ion smoke detector schematic diagram and waveform smoke signal 1 temperature signal/ Kloc-0/ 0000 C20 0500+ military r~~~~ connected with sensors, smoke signal 2 temperature signal 2 00020502 0503 system adopts modular structure, and the programming adopts ladder diagram language. Audible and visual alarm 0504 input 001400152V0505 output 0506 0507 alarm display panel smoke letter ... warm letter ... +24v 0508 0509, address b, address c/ address, material diagram 4, 4PLC system schematic diagram}}}}}. There are always doors, doors, doors, doors, doors, doors, doors, doors, doors, doors, doors, doors, doors, doors, doors, doors, doors, doors, doors, doors, doors, doors, doors, doors, doors, doors. Fire, fire, fire, fire, fire, fire, fire, fire, fire, fire, fire, fire, sound signal and status information: fire alarm, abnormal alarm, fault alarm and display position. The instrument is simple in structure, high in reliability, easy to develop, maintain and popularize, and has highly integrated embedded and modular systems, such as etureand and 15. Key words: mableLogiealController in PROR field, automatic fire alarm, smoke detector, temperature detector, aut 0it 10 litor-III. This automatic fire alarm controller is different from other special fire alarm controllers, and it uses PLC as the control core. Author's brief introduction Zhang Yansheng: geophysical prospecting for coal Institute of China, sensor world 008, reader service card 072750, Yongzhou, Hebei, July 2000.