Circuit Design and Implementation of College English Autonomous Learning Monitoring System

0 Introduction

The Ministry of Education proposed in the overall idea of ​​college English teaching reform: reform the existing teaching model, change the model of teachers, textbooks, chalk, blackboard and students, teachers talking and students listening to a personalized and active learning model with computers (network), teaching software and classroom comprehensive application. The new "College English Course Teaching Requirements (Trial)" also stipulates: focus on and emphasize students as the main body, promote personalized learning and autonomous learning. In order to adapt to the new teaching model, many colleges and universities have set up autonomous learning centers or multimedia teaching centers. However, some problems were found in the autonomous learning teaching practice, such as students cannot persevere, or for various reasons, they eventually give up halfway; autonomous learning becomes a formality, and students play games, surf the Internet or do other things during the autonomous learning process; the autonomous learning equipment has a high failure rate, including student hosts, monitors, headphones and other computer peripherals as well as tables and chairs. Analyzing the reasons, most colleges and universities only monitor the changes in concepts and rules and regulations, but the corresponding rules and regulations are not sound or implemented in place, and the concepts cannot be completely changed, resulting in the lack of effective monitoring of the autonomous learning process and the teaching process of teachers. Therefore, researching equipment that can monitor the autonomous learning process of college English is of great significance to promoting the smooth implementation and effective monitoring of college English teaching reform.

1 Overall design of autonomous learning monitoring system

The monitoring of the English self-learning process is mainly to realize the audio and video monitoring of each self-learning classroom. The monitoring system studied in this project can monitor up to 32 self-learning classrooms, which can meet the current needs of most universities and the system expansion in the future. The overall solution block diagram of this system is shown in Figure 1.

As shown in Figure 1, the video acquisition in the whole system is completed by the camera, the audio acquisition is realized by MIC, and the audio signal is amplified by logarithmic amplification. Since this system can monitor 32 classrooms for audio and video, considering the cost of the acquisition card and the effectiveness of the display (too many classrooms are not convenient for observation at the same time), this system adopts a solution of monitoring 4 classrooms at the same time, and 32 classrooms are monitored in time. At the same time, in order to monitor flexibly, the system uses a matrix switcher to realize the switching selection and monitoring of audio and video. The selected audio and video signals are transmitted to the audio and video acquisition card and displayed and played on the PC. This system uses the Tianmin 10MOONSMD2040 acquisition card. At the same time, the selection of audio and video is controlled by the upper PC (controller), that is, the control command is sent. The control command is transmitted to the main controller of the system through the RS232 protocol. The main controller receives the command, parses the command and controls the corresponding peripherals to execute the command. The peripherals in the system are mainly matrix switchers and terminal controllers. The terminal controller mainly receives the control commands of the main controller for the pan/tilt and aperture, and executes the control commands and audio acquisition and amplification.

2 Circuit Design and Implementation

2.1 Main controller circuit and implementation

Because the main controller and the matrix switcher are installed in the same cabinet and are very close to each other, they can be controlled directly through the I/O port of the microcontroller. To enhance the driving capability, an inverter CD4069 is added to the output I/O port of the microcontroller.

2.2 Matrix switch circuit and implementation

This system is designed for monitoring with a capacity of 32 channels of audio and video. To simplify the design and facilitate debugging, installation, and upgrading, the 32 channels of audio and video are not processed on one PCB board, but are divided into 4 sub-boards. Each sub-board has N8 channels of audio and video, realizing the 8-choice-1 output function of 8-channel audio and video channels, that is, 4 sub-boards form a matrix switcher, realizing the 32-choice-4 output function at the same time. The circuit diagram of each sub-board is shown in Figure 3.

In Figure 3, J1…J8 are relay coils, and double-pole double-throw relay J4078 is used to achieve simultaneous switching of audio and video. J11 and J12 are jumper sockets, which are used to set the address of the sub-board. When the set sub-board address is the same as the sub-board selection address (A0, A1, A2) of the main controller, the 4099 of the sub-board is in working state. At this time, the channel selection instruction (cmd0, cmd1, cmd2) of the main controller is used to make any relay in J1…J8 complete the switching action, so as to achieve simultaneous selection of a certain audio and video.

2.3 Terminal controller circuit and implementation

The terminal controller mainly realizes two functions: one is to control the integrated camera and pan/tilt according to the instructions of the main controller, and the other is to collect the voice signal of the current classroom and process and upload it.

2.3.1 Camera and PTZ Control Circuit and Implementation

As shown in Figure 4, the control command of the RS485 control bus is received by MAX485 and the relay group is controlled according to the command to realize the up/down, left/right rotation of the pan/tilt motor and the zoom, zoom/near, bright/dark adjustment of the aperture motor. The chip MC145027 is used to complete the decoding of the microcontroller command. The microcontroller sends an address command for the selection of the terminal controller and a data command for the control of the terminal controller. Only when the address command sent by the microcontroller is the same as the address set by MC145027, MC145027 will receive the data command of the microcontroller, that is, the control command. Thus, the addressable individual control of each terminal is realized.

2.3.2 Voice signal acquisition and processing

Because we need to collect voice signals from various locations in the classroom (generally within the range of 20 to 50m2), the use of ordinary microphone amplifier circuits obviously cannot meet the requirements. This system uses a logarithmic amplifier circuit for voice amplification, and collects voice signals from various locations within the range of 50m2 more clearly. The designed logarithmic amplifier circuit is shown in Figure 5. IC2 is an operational amplifier, and the system uses LM358 to achieve secondary operational amplification.

3 Conclusion

The effective real-time monitoring of college English autonomous learning is realized by using sensor technology and electronic technology. The design of this system is simple, low-cost, convenient and practical. It plays a very important role in improving students' self-learning consciousness, monitoring the operation of autonomous learning equipment and software platforms, preventing unnecessary losses caused by human damage, and improving the stability and reliability of equipment operation.