Abstract: In order to solve the problem that some major exams require hanging clocks, a new synchronous digital electronic clock system is designed. The power carrier technology is used to realize the remote synchronization control of the electronic clock. The composition and working principle of the system are introduced, and a simple, practical and low-cost synchronous control scheme is provided for the design of the system.
Keywords: synchronous clock; power carrier communication; SC1128; PCF8563
introduction
In recent years, with the development of power line carrier communication (Power Line CommunicaTIon, PLC) technology, power line carrier communication has been widely used in daily life and industrial production, such as power line Internet access, power carrier automatic meter reading system, home automation system, industrial Process control, etc.
Power line carrier communication technology refers to a communication method that uses power line to transmit data and media signals. This technology is to load information carrying high frequency modulation on the current, and then use power line to transmit, and the adapter that receives the information then transfers high frequency modulation information from The current is separated and transmitted to a computer or other corresponding equipment to achieve information transfer. Because the power line carrier communication technology uses power lines as the transmission channel, it has higher transmission reliability, lower line attenuation, and does not require infrastructure investment and daily maintenance costs for communication line construction, making this technology convenient, Low cost and easy to implement.
This article introduces a synchronous digital electronic clock system based on low-voltage power carrier communication technology. Traditional clock synchronization usually requires manual calibration at each clock. This work is not only inefficient, but also has human errors, which cannot meet the needs of modern management. Using a synchronous clock based on power carrier communication not only lowers the cost, but also satisfactorily solves the above problems. The system uses a low-voltage power supply circuit, the clock calibration signal is sent by the host, and the carrier communication module transmits through the power line. After the slave receives the signal, the time is adjusted to realize the synchronized operation of the electronic clock.
1 Overall system structure
1.1 System composition
The system consists of two parts, and its structure is shown in Figure 1. One part is the control terminal of the synchronous clock, as the master system, the other part is the slave system. The structure of all slaves is the same, the number of units is determined according to actual needs, and is not limited. The system uses 220V low-voltage power supply line as the communication medium. The host and slave systems are mainly composed of single chip microcomputer, PCF8563 time chip, SC1128 spread spectrum carrier chip, output power amplifier, band-pass filter, pre-amplifier circuit, coupling circuit, keyboard array input, display output, etc. The host system MCU adopts Atmel's AT89S52 as the control chip, and adds RS 232 or USB serial interface to communicate with the PC. PC can synchronize with Internet time through the network, so that the system can synchronize with Internet time. The slave one-chip computer adopts AT89C2051 as the control chip. The slave is set with a running mode switch, which can work in synchronous running mode or independent running mode. If working in synchronous mode: the clock calibration signal is sent by the host, and the carrier communication module transmits through the power line. After the slave receives the signal, the time is adjusted to realize the synchronized operation of the electronic clock. If working in independent mode: read time from clock chip PCF8563. The user can enter the time or modify the time through the keyboard.
The clock chip adopts PCF8563 designed and manufactured by Philips. PCF8563 is a low-power CMOS real-time clock / calendar chip. It provides a programmable clock output, an interrupt output, and a power-down detector. All addresses and data are serially connected through the I2C bus interface. OK passing.
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