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 4 mm (¼ in) 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 sophisticated controllers that allow irrigation schedules to be automatically adjusted according to the weather have been available for many years, until recently these controllers were out of reach of the average consumer. One type is evapotranspiration controllers or "ET controllers". Several manufacturers are now producing controllers that can be automatically updated by either a simple weather sensor, via a pager that receives a daily update from a network of local weather stations, or through soil moisture sensors. One company has also introduced a product that gathers information from the internet to update the watering schedule Since approximately half of potable water in urban areas is used for irrigation , 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 .
There are two categories in irrigation controllers: Domestic ones for gardening applications, and professional controllers for more demanding agricultural applications. While domestic (gardening) controllers can only open/close a zone (or several zones simultaneously) based on a time duration, without any feedback from the irrigation process, the professional irrigation controllers can irrigate based on volume (quantities defined in cubic meters / Gallons), get the feedback from the process, and can react to actual events happening during the process. For example, a professional controller calculates the actual flow rate running in the system when a specific zone is operated, compare this to its database, and adjust the irrigation process if deviation from the zone's flow rate is detected; This mechanism is called "Flow monitoring", and can prevent irrigation when a burst is occurring in the main line or in the zone's hydraulic components. The controller can also alert the operator locally via its interface, or remotely by sending an SMS or a message to a central control.
The use of smart professional irrigation controllers is constantly increasing as the shortage in water does.