Indoor intelligent lighting control system circuit design—Circuit diagrams read every day (72)

With the rapid development of electronic technology, control systems based on single-chip microcomputer have been widely used in industry, agriculture, electric power, electronics, intelligent buildings and other industries. Microcomputers, as the main body and core of embedded control systems, have replaced the routine of traditional control systems. Electronic circuits. The development and maturity of building intelligence has also laid a solid foundation for the popularization and application of lighting control systems based on microcontrollers. This paper introduces the indoor lighting control system and its principles based on the single-chip microcomputer AT89C51, and proposes an effective energy-saving control method. The system adopts today's relatively mature sensing technology and computer control technology, and uses multiple parameters to control indoor lighting in school classrooms. The system is composed of a single-chip microcomputer as the core and a variety of interface circuits. There are six main parts: AT89C51 chip, optical signal acquisition circuit, human body signal acquisition circuit, clock control circuit DS12887, output control circuit, and timing monitor circuit.

Main controller circuit design

The main controller uses the AT89C51 microcontroller as the microprocessor. AT89C51 is a low-voltage, high-performance CMOS 8-bit microcontroller produced by the American ATMEL company. The chip contains 4K bytes of repeatedly erasable Flash read-only program memory and 128 bytes of random access memory. To obtain data memory (RAM), the device is produced using ATMEL's high-density, non-volatile storage technology and is compatible with the standard MCS-51 instruction system. It has a built-in general-purpose 8-bit central processing unit (CPU) and Flash storage unit. The peripheral interface circuit of the main controller system consists of keyboard, digital display and drive circuit, crystal oscillator, watchdog circuit, communication interface circuit, etc. The hardware circuit schematic diagram of the main controller system is shown in Figure 2-2.

Figure 2-2 Hardware circuit schematic diagram of the main controller system

Design of RS485 communication circuit

In various distributed control systems, one single-chip computer is often used as the host, and multiple single-chip computers are used as slaves. The host controls the operation of the entire system; the slaves collect signals to achieve on-site control; the host and slaves are connected through a bus , as shown in Figure 2-4. The host sends information to each slave (point-to-point) or multiple slaves (broadcast) through TXD, and each slave can also send information to the host, but slaves cannot communicate freely, and information must be transferred through the host. .

The wired communication method of this system uses the RS485 bus for communication. The RS485 standard supports half-duplex communication. Only three wires are needed to send and receive data. At the same time, it has the ability to suppress common mode interference. The receiving sensitivity can reach ±200mV, greatly The communication distance is improved. At the 100K bps rate, the communication distance can reach 1200m. If the communication distance is shortened, the maximum rate can reach 10M bps. The master-slave communication method is used here, with the host machine acting as the main controller and the slave machine acting as the sub-controller. The master is in a dominant and dominant position, and the slaves receive and send data in an interrupt manner. The information sent by the master can be transmitted to all slaves or designated slaves. The information sent by the slaves can only be received by the master, and the slaves cannot Direct communication. The communication circuit diagrams of the master and slave are shown in Figure 2-5 and Figure 2-6 respectively.

Figure 2-5 Host communication circuit diagram