Controller (irrigation)
Encyclopedia
An irrigation controller is a device to operate automatic irrigation
Irrigation
Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...

 systems such as lawn sprinklers and drip irrigation
Drip irrigation
Drip irrigation, also known as trickle irrigation or microirrigation or localized irrigation , is an irrigation method which saves water and fertilizer by allowing water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves,...

 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 sensor
Rain sensor
A rain sensor or rain switch is a switching device actuated by rainfall. There are two main applications for rain sensors. The first is a water conservation device connected to an automatic irrigation system that causes the system to shut down in the event of rainfall...

s, soil moisture sensors
Soil moisture sensors
Soil moisture sensors measure the water content in soil. A soil moisture probe is made up of multiple soil moisture sensors. One common type of soil moisture sensors in commercial use is a Frequency domain sensor such as a capacitance sensor...

, weather data, remote operation, etc.

There are two basic types of controllers, electric and hydraulic. Most automatic irrigation valves are diaphragm valve
Diaphragm valve
Diaphragm valves consists of a valve body with two or more ports, a diaphragm, and a "saddle" or seat upon which the diaphragm closes the valve. The valve is constructed from either plastic or steel....

s 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 electromechanical or electronic controllers. In this scenario, the controller is connected to an electrical circuit that operates a solenoid
Solenoid
A solenoid is a coil wound into a tightly packed helix. In physics, the term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. Solenoids are important because they can create...

 attached to each valve (solenoid valve
Solenoid valve
A solenoid valve is an electromechanical valve for use with liquid or gas. The valve is controlled by an electric current through a solenoid: in the case of a two-port valve the flow is switched on or off; in the case of a three-port valve, the outflow is switched between the two outlet ports...

). 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
Evapotranspiration
Evapotranspiration is a term used to describe the sum of evaporation and plant transpiration from the Earth's land surface to atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies...

 controllers or "ET controllers". Several manufacturers are now producing controllers that can be automatically updated by either a simple weather
Weather
Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...

 sensor, via a pager
Pager
A pager is a simple personal telecommunications device for short messages. A one-way numeric pager can only receive a message consisting of a few digits, typically a phone number that the user is then requested to call...

 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 . With approximately half of potable water in urban areas being used for irrigation , and many homeowners either not taking the time to regularly adjust the programming on their controllers or simply not knowing how, these "smart controllers" have been shown to be helpful in achieving water conservation
Water conservation
Water conservation refers to reducing the usage of water and recycling of waste water for different purposes such as cleaning, manufacturing, and agricultural irrigation.- Water conservation :Water conservation can be defined as:...

 .

There are broadly two categories of irrigation controllers: domestic ones for gardening applications, and professional controllers for more demanding agricultural applications.
While most domestic (gardening) controllers can only open/close zones based on a time duration, without any feedback from the irrigation process, professional irrigation controllers can irrigate based on volume (quantities defined in cubic meters / Gallons), receive feedback from the process, and react to actual events happening during the process.

For example, the typical professional controller will calculate the actual flow rate running in the system when a specific zone is operated, compare this to a pre-configured required amount, 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
SMS
SMS is a form of text messaging communication on phones and mobile phones. The terms SMS or sms may also refer to:- Computer hardware :...

or a message to a central control.

The use of smart professional irrigation controllers is constantly increasing as the shortage of water does.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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