The Design And Application Of The Temperature Control System Based On The SCM In The Greenhouse

With the popularization of greenhouse technology, the amount of greenhouse is larger and larger. However, the temperature control of greenhouse is becoming a difficult problem. Currently, the temperature control system of greenhouse is mostly using a transfers system which consists of analog temperature sensors, multiplexing analog switches, A/D conversion units and SCM. 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. Thus the work of fixing and take-down is miscellaneous, and the cost is high. What's more, what is transferred in the system is analog signals which are easily interfered and have more ullage. It is hard for the controller to make a decision in time according to the change of temperature because the measure error is bigger. So under this circumstance, it is necessary to empolder a real time and precise temperature control system which is in a position to deal with temperature information of many nods.This paper gives a greenhouse temperature control project which is based upon the SCM and digital monobus technology. In this project, the change of temperature in the greenhouse is transformed into the change of electric current and then into the change of voltage by using the temperature sensors. The change of voltage is input into the A/D conversion units and the result is dealt with by SCM. At last the real time temperature in the greenhouse is displayed on the monitor under the control of SCM. Once the value of the temperature in the greenhouse exceeds the minimum and maximum which is preestablished, the SCM will give an alarm and autocontrol the temperature in the greenhouse. This project can make real time patrol checking to the different nod's temperature in the greenhouse, and every separate checking unit can finish its task independently. At the same time, very separate checking unit can make timing collection according to the instruction from the main control, and the measure results can not only be displayed at home but also can be further processed and be kept in the archives by using the SCM's serial interface and RS-485 bus andcommunication protocols. This temperature control system whose stabilization and maintainability is good doesn't need any fixed network to support and is easily fixed.