Design And Study On Automatic Control System Of Dual Humidity Based On Greenhouse Microirrigation

This paper expounds the hardware layout, software development and reliability design of dual humidity automatic measurement and control system with singlechip microprocessor in detail. Based on the AT89C51 singlechip microprocessor, the whole system consists of sensor circuit, signal transfer circuit, peripheral device interface circuit, output control circuit and malfunction alarm circuit as well as system software. This system can control multi-input and multi-output. It can work in several methods such as closed-loop control with sensors, opended-loop control. In addition, it has automatic alarm function when the system cannot work mormally or the humidity exceeds the preset range.In hardware design, the HM1500 capacitive moisture sensor is chosen as the air humidity sensor and the SWR as the soil humidity sensor, ADC0809 as the A/D converter, independent key as the keyboard, LED digital tube as the display device, the simple piezoelectric buzzer as the alarm device, DB25 as the printing interface communicating with PC. The output control circuit is composed of triode, photoelectric coupler, relay and so on. In order to meet the input and output requirements of the system, 825 5 A is chosen to expand the I/O interface of the AT89C51. The system software design adopts the fashionable modularized structure .The development of system software applies assembly language completely. The main programs include system monitor and control program, keyboard-scanning subroutine, keyboard state analysis subroutine, A/D sampling subroutine, parameter-preseting subroutine etc. At the same time, the efficient anti-interference measures are adopted in the design of the hardware and software in orderto improve the reliability of this system-MAX706 as microprocessor monitor device, for example.The successive emulating debug experiments show that the system takes on the character of higher reliability&stronger control function and can meet the anticipated requirements. It can be suitable for China and be redeveloped according to detailed needs. At last feasible suggestion about further development and improvement of this system is made in this paper.