The design of the AT89C51 used as the core control components， Design of a simple The program to AT89C51 as controlling core， and the keyboard loudspeakers core modules in the main control module on the main control module has 16 keys and According to users of the parade want to play for free expression in Music is one of many components of different scales， each scale corresponds to different frequencies， This way we can use a different frequency combinations， which may constitute what we want music， Of course microcontroller to generate different frequencies very convenient， We can use SCM timer / counter T0 to create square wave frequency signals， therefore， As long as we put a song of the tune the frequency response relationship can get Keywords : microcontroller， buttons， speakers，
With industrial development in recent years， process control for precision and reliability of more higher requirements， and also toward the liquid level control functions， control of a flexible， simple operation， precise control precision Liquid level regulator is a very wide application of the production of liquid level measurement and control equipment， so the accuracy of measurement and control accuracy is the key to the Available in the traditional liquid level regulator on the basis of the design using AT89C51 single-chip microcomputer as the core， hardware， including: A / D conversion circuit ADC0809， D / A converter circuit DAC0832， keyboard display chip 74LS165， 74LS164， the use of external data memory PCF8583， V / I conversion circuit， power circuit， and these constitute a single-chip level-conditioning Software， including PID control algorithm， level The system applies to the single-chip control of liquid level measurement， not only to enhance the product's features and quality， and reduced The system also has advanced and reasonable structure， function and meet the requirements of control precision， strong anti-interference ability， high flexibility and reliability， versatility， and low prices， easy to use and so
