Controller (irrigation)
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An irrigation controller is a device to operate automatic irrigation systems such as lawn sprinkler systems and drip irrigation systems. Most controllers have a means of setting the frequency of irrigation, the start time, and the duration of watering. Some controllers have additional features such as multiple programs to allow different watering frequencies for different types of plants, rain delay settings, input terminals for sensors such as rain and freeze sensors, weather data, remote operation, etc.
A new controller, the CommonSensor, enabling autonomous irrigation by the plant, has been introduced recently. The controller opens and closes a selenoid valve at a preset soil water tension, keeping the soil nearby wet. An intensive root system that develops near the controller dries the soil and drives the autonomous irrigation. Using autonomous irrigation with the new controller, both irrigation scheduling and volume of water applied are autonomous, without human interference. Errors in irrigation are eliminated since the plant senses and integrates both environmental condition and available soil water. Furthermore, the autonomous irrigation compensate for errors in the layout of an irrigation system (number of laterals and drippers) by increasing the frequency of irrigation.
There are two basic types of controllers, electric and hydraulic. Most automatic irrigation valves are diaphragm valves, in which the water above the diaphragm must be discharged for the valve to open. In a hydraulic system, the controller and valves are connected via small plastic tubes approximately 1/4" (4 mm) in diameter. The controller opens the tube connected to the valve, allowing that valve to open.
Most newer systems employ electric controllers. In this scenario, the controller is connected to an electrical circuit that operates a solenoid attached to the valves. When the solenoid is actuated, the water above the diaphragm is relieved and the valve opens.
Although for years sophisticated controllers that allow the programming to be automatically adjusted according to the weather have been available, until recently these controllers were out of reach of the average consumer. Several manufacturers are now producing controllers that can be automatically updated by either a simple weather sensor or via a pager that receives a daily update from a network of local weather stations. Since approximately half of potable water in urban areas is used by landscape, and many homeowners do not know how or do not take the time to regularly adjust the programming on their controllers, these "smart controllers" have been shown to be helpful in achieving water conservation.
