CAN based actuation system for greenhouse control

This paper describes an actuation system for greenhouse control. It was built over a previously developed controller area network (CAN) system, based on the P80C592 microcontroller from Philips implementing a hierarchical structure to form a bus topology. In this network a personal computer (PC) is connected through an interface board to stations, located at the greenhouse. These stations are implemented using a serial linked I/O device (SLIO) from Philips, making possible greenhouse control. This choice is based on the SLIO's low price and suitability for applications where no high-speed requirements are needed such as on/off functions. When more complex actuation tasks are needed, more intelligent nodes had been designed, based on the P80C592 microcontroller. The assembling of the actuators within a greenhouse allows the use of a wired architecture. As a means of communication, the CAN protocol is used, which has a great flexibility and robustness needed in real-time control. The system allows easy expansion and configuration without compromising its performance. This is the case when the parameters must be changed whenever the weather conditions (summer/winter), force modification of the set-points of several control variables such as temperature, light and humidity, among others.