Design of an intelligent warning device for outdoor high-voltage devices

introduction

With the continuous advancement and deepening of the national rural power grid transformation work, the power network conditions and distribution equipment in rural areas of my country have been fundamentally improved. In each township or village, a group of distribution transformer equipment will be set up outdoors far away from residential areas. The transformer equipment is responsible for the normal power supply of industrial and agricultural production in the surrounding areas and people's daily life. These transformer and distribution equipment are all high-voltage dangerous devices. Close approach or contact by non-professional operators may constitute serious safety accidents. At present, the vast rural areas of my country usually use painting or hanging warning signs in these outdoor high-voltage distribution equipment sites to remind people of the dangers of the high-voltage area. However, these methods have great limitations in warning different groups in rural areas, and various electric shock accidents involving people and animals have occurred repeatedly.

The author has developed a stable, reliable and practical intelligent warning device that can be easily installed in these high-voltage dangerous places, and can provide reliable and timely warnings to people and animals entering the high-voltage dangerous areas, thereby effectively protecting people's lives and property.

System hardware circuit

The designed intelligent alarm device is mainly composed of a circuit controlled by an AT890S52 single-chip microcomputer, including a Chinese character warning LED display circuit, a pyroelectric infrared detection voice alarm circuit and peripheral circuits. The system circuit structure block diagram is shown in Figure 1. Among them, the Chinese character warning LED display circuit uses a display screen composed of 16 monochrome high-brightness 8×8 LED arrays to display 4 Chinese characters at a time, dynamically changing and cyclically displaying warning slogans; the pyroelectric infrared detection voice alarm circuit uses a pyroelectric infrared detection sensor to continuously detect the surrounding area. When a person moves within the effective range of its infrared detection, the detector will send the captured signal to the single-chip microcomputer, and then the single-chip microcomputer controls the response to voice alarm and prompt.

Chinese character warning LED display circuit

The circuit connection of the LED array unit that displays a Chinese character is shown in Figure 2. It consists of chips IC1~IC3, NPN transistors Q1~Q16, current limiting resistors R1~R32 and 4 single-color high-brightness 8×8 common anode LED modules. The circuit adopts a high-state row scanning method, that is, at any time, there is only one high-level signal in the output of the scanning signal through 74LS154, and the others are low-level signals. After a row is scanned, the high-level signal is transferred to other adjacent rows. The scanning signal is connected to the base of an NPN transistor. When the high-level signal scanning signal is input, the emitter current of the transistor will flow into the row pin of the LED array, which can make the LED in the row have the conditions to light up [1]. Under the control signal, the two 74LS373 latches latch the character data sent by the shared eight data lines P0.0~P0.7 respectively, and provide them to the column pins of the LED array, so as to form the corresponding Chinese characters on the display screen composed of 4 8×8 LED arrays.

[page]

This intelligent alarm device contains four such unit circuits and can display four Chinese characters at the same time.

Pyroelectric infrared detection circuit

The core component of the pyroelectric infrared detection circuit is the pyroelectric infrared GH-7181 module, which has a detection distance of about 7 meters (the required detection distance can be easily adjusted by adding isolation films of different thicknesses on its surface). The detection area is fan-shaped with an angle of about 110 degrees. Four infrared detection head devices are installed around the high-voltage equipment to ensure reliable detection of people or animals entering the detection range over a large area without blind spots [2-3].

The pyroelectric infrared detection wiring circuit is composed of four infrared probe modules, transistor Q17, capacitor C1 and resistors R33~R35 (see Figure 3).

When a person or animal moves within the infrared detection range, a set of pulse signals will be generated at point A. The pulse signals will be sent to the microcontroller through the P1.6 pin for judgment and response.

Voice alarm circuit

[page]

The voice alarm circuit consists of chips IC4 and IC5, capacitors C2 to C7, potentiometer W1 and a speaker. The wiring is shown in Figure 4. In the figure, IC4 is an ISD4000 voice chip, which contains an oscillator, an anti-aliasing filter, a smoothing filter, an audio amplifier, an automatic squelch and a high-density multi-level flashing storage array [4]. When the P1.6 pin of the single-chip microcomputer receives the pulse signal triggered by the infrared, the rising edge signal of P1.0 is set to the 1 pin of the ISD4000 chip, making it in the chip select working state, thereby sending the internal preset audio signal to the input end of the LM386 through the 13th pin (AUOUT), and driving the speaker to play after the power amplifier. If the preset voice in the ISD4000 chip is stored in multiple segments, the chip's 2 pins (MOSI) and 3 pins (MISO) need to be connected to the two idle I/O ports of the single-chip microcomputer respectively, and the voice signal of a certain segment is selected for output through the single-chip microcomputer control command.

Circuit power supply

The circuit power supply uses JYUS-10W AC/DC micro-switching power supply, which can stably output 5V/2A DC signal under the dynamic voltage signal range input state between voltage amplitude (85V～265V) and frequency (45HZ～65HZ).

System software programs

[page]

The system program mainly includes the main program, Chinese character warning LED display subroutine, infrared detection subroutine, voice alarm interrupt subroutine, etc. The program flow chart is shown in Figure 5.

System initialization mainly includes: pin configuration initialization, system parameter initialization and timer setting, etc. The Chinese character warning display subroutine calls the warning code program to complete the display of Chinese characters. This part of the display program can be modified to various display modes according to the needs of different users. The infrared detection subroutine mainly scans and determines whether there is a pulse on the P1.6 pin of the microcontroller. If no pulse appears, it returns; if a pulse appears, the voice alarm interrupt subroutine is called through the control instruction, and the audio signal preset in the ISD4000 voice chip is played through the speaker to complete the voice warning function.

Conclusion

This system uses a high-brightness monochrome LED array to display Chinese characters for warnings, which are clear and eye-catching both during the day and at night. It is also equipped with infrared detection and voice alarm. The system rationally combines the visual and auditory warning functions, making it more humane. When used outdoors, this device needs to be equipped with some rain and lightning protection facilities. The device has passed the experimental stage and has begun to be used in some rural areas in the north. After being improved and equipped with temperature and humidity detection and upper computer data recording systems, this system can also be used in various environmental monitoring and security places such as granaries, library archives, etc. [5]. It is less affected by specific environmental factors, is easy to install, and has a wide range of applications.

References:

[1] Zhang Yihe, Chen Dibei. Example 8051[M]. Posts and Telecommunications Press, 2006

[2] Li Guanghua. Practical application of infrared and microwave probe alarm system [J]. China Security, 2005(21)

[3] Chen Youqing. Infrared induction high voltage alarm[J]. Electronic Production, 2001(9):12-13

[4] Fan Hanbai, Chen Xusheng, Li Xuemei. Design of intelligent recording and playback system based on ISD4000 series chips[J]. Application of Electronic Technology, 2007(11):44-46

[5] Li Xudong. Application research and design of digital security system[J]. Security Technology, 2008(3):35-36