Intelligent video surveillance signal acquisition circuit module design

The terminal controller mainly implements two functions. One is to control the integrated camera and PTZ according to the instructions of the main controller. The other is to collect the voice signals of the current classroom and process and upload them.

Camera and pan/tilt control circuit and implementation: MAX485 receives control instructions from the RS485 control bus and controls the action of the relay group according to the instructions to realize the up and down, left and right rotation of the pan/tilt motor and the zoom, zoom out/near, and zoom of the aperture motor. Light/dark adjustment. The chip MC145027 is used to complete the decoding of the microcontroller instructions. The microcontroller sends address instructions to select the terminal controller, and sends data instructions to control the terminal controller. Only when the address command sent by the microcontroller is the same as the address set by MC145027, MC145027 receives the data command from the microcontroller, that is, the control command. This enables addressable individual control of each terminal.

matrix switcher circuit

This system is designed for monitoring with a capacity of 32 channels of audio and video. In order to simplify the design and facilitate debugging, installation, upgrade, etc., the 32 channels of audio and video are not processed on one PCB board, but are divided into 4 sub-boards, each sub-board. The N8 audio and video channel on the board realizes the output function of 8 out of 8 audio and video channels, that is, 4 sub-boards form a matrix switcher to realize the 4 out of 32 output function at the same time. The circuit diagram of each daughter 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. This jumper sets the address for the subboard. When the set subboard address is the same as the subboard selection address (A0, A1, A2) of the main controller, the 4099 of the subboard is in working status. , at this time, use the channel selection instructions (cmd0, cmd1, cmd2) of the main controller to make any relay in J1...J8 complete the switching action to realize the simultaneous strobe of a certain audio and video channel.

Voice signal collection and processing circuit

Because it is necessary to collect speech signals from various locations in the classroom (generally within the range of 20~50m2), using ordinary microphone amplifier circuits obviously cannot meet the requirements. This system uses a logarithmic amplification circuit for voice amplification, and can relatively clearly collect voice signals at various locations within a 50m2 range ^. The designed logarithmic amplifier circuit is shown in Figure 5. IC2 is an operational amplifier, and the system uses LM358 to realize the second-level operational amplifier.

The system design using sensing technology and electronic technology is simple, low-cost, convenient and practical. It plays a very important role in improving students' awareness of independent learning, monitoring the operation of independent learning equipment and software platforms, preventing unnecessary losses caused by man-made sabotage, and improving the stability and reliability of equipment operation.