Research And Development Of Dirct Digital Control's I/o Module

Direct digital control (DDC) is now mainly used in building control systems and end of the control system for the central air-conditioning. DDC which can be run independently is an independent control procedures and basic mathematical models and algorithms, including the controlled system to complete all the elements of process control. Through the development of the new generation of direct digital controlling Step600, it will greatly enhance the Ao-Yu company's Step product performance and value, at the same time, it will lay the foundation for the development of a dedicated controller.The number of DDC input and output port's points is an important indiicator to evaluate a DDC controller. The controller of Step600 includes a main controller and five expansion I/O modules, the port could reach 168 points. In order to meet Step600 controller's universal design requirememts, developed analog signal input port that can be collected 0~10V Voltage, 4~20mA current, PT1000 resistors and NTC resistors. Analog voltage output port can output 0~10V Voltage. In order to Step600 can accord to the size of controller system to flexible configuration I/O modules, the main controller and expansion module via SPI communications. As the controller working environment has become more difficult, there are a lot of protection circuit and antijamming circuit in the I/O circuit design.To facilitate the DDC control system for collecting data, develop the wireless temperature and humidity sensor module based on Zigbee protocol. The sub-nodes of wireless module includes digital temperature and humidity sensors, CPU circuit and Zigbee module. Central node includes RS485 communications circuits, CPU circuit and Zigbee modules. Because the route's mode is free routing between sub-nodes, centrol node can collecte an effective data far from 200 meters. Center node meets the Modbus protocol, so the module can be working with the PC host computer, and all to meet the Modbus protocol compatible controller.The prototype has succussed to applicated in the central air-conditioning system of the laboratory, which verifies the Step600 contoller's performance and functionality to meet the design requirements. Step600 controller has a high accuracy signal acquisition, as well as live output capability-driven, which can meet the applications for higher control performance requirements.