Temperature Control Systems Of Greenhouse Based On The Mcu

Currently, the temperature control system of greenhouse is mostly using a transfers system which consists of analog temperature sensors, multiplexing analog switches and A/D conversion units. This kind of temperature collection system needs a lot of cables which is laid to make the signal of the sensor be sent to the collection card in the greenhouse, and the work of fixing and take-down is miscellaneous, and the cost is high. What's more, the analog signal transferring in the system which is easily interfered and alleged, and the measure error is bigger, this is hard for the controller to make a decision in time according to the change of temperature. So under this circumstance, it is necessary to employ a real time and precise temperature control system which can deal with temperature information of many nods.The main idea in this paper is to design a computer distributed auto-control greenhouse system. The system is made up of one PC and a control device which treat MCU as the core, and the data is transmitted by RS-485 bus communicat network. The local operation status in greenhouse can be obtained by monitoring environment parameters and these information be stored in PC. This paper gives a greenhouse temperature control project which is based upon the SCM and digital monobus technology. The main content of this paper are as follows:1.Studied the important temperature parameter in greenhouse, and analyzed the methods of regulatory control.2.Through studying the auto control system of intelligent greenhouse, a distributed control system can achieve realize real-time monitoring and control of greenhouse temperature is obtained from using sensor, communication and auto-measure technologies.3.The paper describes the structure of the distributed control system, which consests host computer and lower computer, and the host computer utilizes RS-485 to communicate with the lower computer and provide friendship human machine interface (HMI) for facilitating communication and setup of the data. The lower computers that administer the data acquisition system using the AT89S51 Microcontrollers can operate separately.4.The design of RS-485 interface we proposed can communicate among several net nods in distant range and implement temperature measurement and control of multi-point.5.The users can set parameter base on the need of plants, by auto controlling of the system, temperature parameters of greenhouse can be in the best, and the greenhouse can provide plants a good growth environment. When parameters overrun the deadline, the system can make sound-light alarm.6. The achievements of this paper are summed up, and the future work is prospected.