Foreword
With the rapid development of the national economy and the continuous expansion of the city's scale, industrial and commercial enterprises have gradually increased, new residential communities have emerged, and the floating population has increased rapidly. These have brought about economic prosperity and the continuous improvement of people's living standards, as well as the entire city. The comprehensive management and security guarantees have brought many negative impacts and problems. Fires, theft, and gas leaks have seriously affected people's lives and property and normal living order. How to improve the overall security system of large and medium-sized cities and enhance the city's comprehensive management capabilities is an important issue in the relevant government departments.
In this regard, after analyzing and comparing the practical applications of similar systems and products at home and abroad, we launched the “Urban Intelligent Security Integrated Management Systemâ€, which uses computer and network topology technology, with the city monitoring and management center as the hub, with intelligence The control terminal is a service object, scientific, systematic and digital from the aspects of establishing scheduling, monitoring, integrated management and information release, making full use of modern remote sensing technology (RS), geographic information system technology (GIS), office automation technology ( OA), Global Positioning System (GPS) and modern communication and network technologies, establish and improve a comprehensive "Urban Intelligent Security Integrated Management System." The system has been tested in the provincial capital city, and the effect is good.
The new terminal monitor is a control unit that performs bidirectional real-time data exchange with the control center, local control execution, and provides relevant user terminal information at any time. It is an important part of the urban intelligent security integrated management system network.
Overall design and main technical functions
The design of the new terminal monitor is mainly considered from the application of the security monitoring and management subsystem and the user's off-network use to meet the requirements of two-way data transmission and local service, ensuring the controller is stable and reliable, the user operation is simple and practical, reducing false alarms and improving the accuracy of the alarm.
1: It adopts world famous IC microcomputer chip, with perfect functions, high integration, strong anti-interference and excellent EMC (electromagnetic compatibility).
2: Take the lead in using the caller ID detection circuit to actively identify and monitor incoming calls and user private calls, and reduce the interference of ringing to the user.
3: Set dual-tone multi-frequency automatic dialing circuit and decoding circuit to meet the two-way data transmission and individual monitoring of the network.
4: Intelligent alarm sequencing design, which can be automatically identified and processed according to the alarm priority level. 5: The microcomputer contains permanent memory, and the current working parameters are permanently saved when the power is turned off, and the original working state is maintained when the call is made.
6: It is suitable for multi-standard and multi-model sensor input. It can effectively process both switching signal and pulse electric signal input. The microcomputer contains 10-bit analog/digital conversion unit. The input signal resolution can be as low as 4mV, which greatly improves the alarm work. Reliability, effectively preventing false positives.
7: The monitor is designed with a number of self-test circuits to detect the main functions at any time, fault reporting and local prompts. 8: Equipped with engineering keyboard installation interface and user infrared remote control to meet different needs.
Hardware circuit design functional block diagram
Introduction to main circuit design
Automatic off-hook telephone interface circuit
The hardware principle is shown in Figure 3. The rectifier bridge provides polarity conversion. The photocoupler TLP521-1 circuit unit provides ringing current detection. The triode Q1 and Q2 circuit units provide off-hook load and dual-tone multi-frequency (DTMF) output. When working, the MCU sets port RB0 to be valid for the falling edge of the interrupt input, and RB1 is the output control port. When there is no incoming call, RB0 is high level and there is no signal transition. When a ringing current arrives, the photocoupler TLP521-1 is turned on, RB0 is low level, and after several effective interrupt counts, the ringing current is confirmed. If it is valid, RB1 outputs a high level, and drives the high-voltage transistor Q2 to conduct. After the polarity is changed by the load circuit, the voltage is reduced to about DC 8V, and the off-hook is completed automatically. The working circuit is simple and practical, and the work is stable and reliable. The load characteristics of the interface circuit conform to the relevant standards of the telecommunications, and the circuit characteristics of the commonly used 1:1 isolation transformer for the off-hook interface are changed, the cost is reduced, and the productivity is improved.
Caller ID detection circuit
BELL202 data stream protocol
Caller ID (ie, calling number identification) has become an important function in telephone communication. It is indispensable in many switch and customer service call centers. Most of the ordinary telephone users have also been opened, but they are used in security monitoring systems. There are few reports in the middle. Our company took the lead in developing and applying this technology in the new terminal monitor of urban intelligent security system, which laid a good foundation for improving the overall performance of the system and improving customer service.
Calling number identification is a method of transmitting information such as the calling telephone number to the called party in the call phase of the telephone according to the V.23 or BELL202 data stream protocol (ie, Caller ID). The typical Caller ID protocol consists of The following three levels are composed:
Physical layer: asynchronously transfers 8-bit characters through the physical layer, including start and stop bits and 6-bit data. Data link layer: The link layer combines content data frames into one data packet. The data format is as follows:
Schematic layer: The data format is as follows:
FSK (frequency shift keying)
FSK (Frequency Shift Keying) is a modulation method for binary transmission of data on a telephone line. It uses different carrier frequencies to represent binary data "0" and "1". It has high data transmission efficiency and good anti-interference ability. specialty.
Circuit principle and working process
In this unit circuit, our company designs the FSK (Frequency Shift Keying) decoding chip of MT88E39 of American MITEL Company. The device is a 16PinSOIC package, 5 input pins, 8 output pins, 1 pair of power pins, and 1 internal connection pin, as follows:
(1) Pins 1 and 2: The analog input terminals IN+ and IN- of the op amp are input from the FSK modulation signal.
(2) Pin 3 (GS): Op amp gain adjustment terminal.
(3) Pin 4 (VRE): Reference voltage output (2.5V).
(4) Pin 5 (CAP): External 0.1 F ceramic capacitor access terminal (grounded at the other end).
(5) Pins 6 and 7 (OSC1 and OSC2): The connection terminals OSC1 and OSC2 of the crystal oscillator. OSC1 clock input, OSC2 is the clock output.
(6) Pin 9 (DCLK): Different functions in different working modes. In mode 0, it is the serial data output bit synchronous clock. When there is no FSK signal input, it is high level; when there is a signal, its rising edge indicates that the data bit is stable and can be read. In mode 1, it is the input and needs to be connected to the read signal of the microprocessor.
(7) Pin 10 (DATA): The serial data output terminal is high when there is no FSK signal input. When there is a signal, each byte is in the low position and the high bit is sent out.
(8) Pin 11 (/DR): A data word is ready for the flag signal, that is, the output word sync clock.
(9) Pin 12 (/CD): The carrier is detected during the specified time.
(10) Pin 13 (PWDN): Low power operation control input. The high level is disabled and the op amp, oscillator, and internal circuitry are not working.
(11) Pin 14 (MODE): The operation mode selects the input terminal and is divided into mode 0 and mode 1. The difference between the two-clock mode is only the interface between the data output and the microprocessor. Mode 0 is used more.
(12) Pin 15 (IC), internal connection, and line data output.
(13) Pins 8 and 16 (Vss, Vdd): A pair of power pins.
In the circuit, we choose MT88E39 for working mode 0, disable low power mode, and the data signal (DATA) receiving baud rate is 1200B/s. When the valid ringing signal is detected, the MCU port RA1 monitors the MTCLK of the MT88E39 pin 9 at any time. When there is a falling edge transition, the port RA2 has a baud rate of 1200 (internal timing of the MCU) from the MT88E39 pin 10 DATA (data output) After obtaining valid data, the caller ID identification work is completed after analyzing the BELL202 data stream protocol format.
Case Analysis
This example is the FSK data received from Chengdu Telecom Bureau of Sichuan Province. The calling number is mobile phone 13980818810, the called number is 85141190, and the caller ID sample data is: 0X55, 0X55...0X55, 0X55, 0XFB, 0X04, 0X13, 0X310X30 , 0X31, 0X38, 0X31, 0X30, 0X30, 0X35, 0X31, 0X33, 0X39, 0X38, 0X30, 0X38, 0X38, 0X31, 0X38, 0X37, 0X30, 0X53 Data Explanation: 1 channel valid data: 0X55, 0X55...0X55 The number of 0X55 varies from 24 to 32, and is related to the first ringing start. 2 Start signal: 0XFB This data changes every time. 3 Information type: 0X044 Data length: 0X135 Talk time ASCII code: 0X31, 0X30 , 0X31, 0X38, 0X31, 0X30, 0X30, 0X35 analysis for October 18, 10:05 6 caller mobile phone number 13980818870: 0X31, 0X33, 0X39, 0X38, 0X30, 0X38, 0X38, 0X31, 0X38, 0X37, 0X307 Checksum: 0X53
Audio dialing circuit
The DTMF dual-tone multi-frequency dialing IC in the audio dialing circuit uses the HT9200A of Taiwan Hetai Technology Co., Ltd. The chip series includes HT9200A, HT9200F, HT9200B and other series, of which 9200A input signal is serial port receiving mode; 9200F and 9200A receiving mode are the same, but the clock only allows external input, the chip increases the chip select start signal; 9200B input signal is 4 Line parallel port receiving method. Taking into account the cost and system requirements, we chose the HT9200A model. Due to the insufficient dual-tone multi-frequency amplitude at the DTMF output, the first-level triode driver is added with good results.
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Dongguan XINYUDA Technology Co., Ltd. , https://www.gdxige.com