Controllers were once a simple clock that could only be programmed to start and stop sprinkler run times, regardless of actual weather and soil conditions. Today’s controllers, known as smart controllers, are far more advanced than those earlier models, and if you don’t have one, you really should think about upgrading. Not only do they reduce water waste, but they’ll also save you money. In communities where there are watering restrictions, smart controllers can keep your plants and lawn healthy within conservation watering schedules. Austin Water even has a rebate program for irrigation upgrades.
Here are some of the features available in the current generation of smart irrigation controllers:
- Programmable using a computer, tablet, or smartphone. The system’s current status can be viewed and changes made to the program remotely. Programming can also be done manually at the panel.
- Flow sensor data. The flow sensor will shut down the system if it detects a flow higher than the programmed limit, which could indicate ruptures or leaks.
- Rain sensor data. The controller will shut down the system if a specific amount of rain has fallen, or even prevent the system from starting if rain is detected.
- Soil moisture sensor data. The controller won’t start the system if it senses the soil is wet enough.
- Freezer sensor data. The controller won’t turn on if the temperature drops to a specific degree (e.g. 37 degrees).
- Wind sensor data. The controller will shut off the irrigation system during periods of high wind (shut down points are adjustable), then automatically reset the system when conditions are more favorable.
- Daily weather data received either remotely, or from an on-site weather station, and used to determine watering needs.
- Detailed statistical reports and charts provided to allow users to track water usage and manage scheduling.
- Automatic notifications of failure alerts sent by email or text to a technician and/or home owner.
- Operates without WiFi.
- Allows customized watering for zones.
- Works with digital assistants, so you can start or stop your various zones with a voice command.
- This document provides a comparison of smart controllers, including detailed information about each controller’s capabilities and specifications. There’s also a list of definitions used with smart controllers at the end of the document.
There are two types of smart controllers: weather-based or evapotranspiration (ET) controllers, and soil moisture-based controllers.
Weather-Based ET Controllers
Weather-based ET controllers use weather data derived from evapotranspiration (ET) calculations (the sum of evaporation from the land surface plus transpiration from plants) as a basis for scheduling irrigation. ET is used to determine when and how much irrigation water is needed, and is usually expressed as the depth of water in inches or the volume of water in gallons used by a planted area for a period of a day, week, month or year. The best ET weather data uses temperature, relative humidity, wind speed, and solar radiation for its calculations. There are generally four types of ET controllers:
Historical ET Controllers
These use historical weather and water use data for your area to determine what amount of water is required. Usually it only resets the time monthly. The historic data is not perfect, but for most users it still gives significant water savings. Occasionally, you will have to override the automatic control settings, especially if you have unusually hot weather for the month. On some models you only have to enter your zip code to set up the controller, and it accesses the historic data from its memory. On other models you have to manually key in the historic data from the user’s manual or a website.
Historical ET Controllers With a Sensor
These controllers use historical data to determine watering time, but then adjust the time based on a sensor, either a temperature or solar radiation sensor. This combination is more accurate than just using the historical data alone. If the daily high temperature is higher than the historical data, the controller adds more time. If the temperature that day is lower, the controller reduces the watering time.
Signal-Based Controllers
This type of controller uses water and/or weather data provided by a remote provider. The controller receives data from either a central data provider, or from a local weather station via radio, the Internet, or a mobile device. Usually there’s a subscription charge for the data service, as well as charges for the smartphone, tablet, Internet, or radio link. The data can be very accurate if it comes from a nearby weather station. It can also be very accurate if it comes from a central database of historic data that is managed expertly for current conditions.
On-Site Weather Measurement Controllers
These controllers have their own weather stations you install with it that calculate ET continuously, and adjust the irrigation times according to weather conditions. Such sophisticated controller systems can provide accurate data if the sensors are high quality, positioned according to required standards, and well-maintained to keep them functioning.
Soil Moisture-Based Controllers
This type uses sensors to determine the moisture content of the soil. Moisture sensors are buried at the root zone level of turf, trees, or shrubs, to measure the actual amount of moisture in the soil and transmit this information to the controller. The system compares this reading to the recommended moisture level for the plant, soil type and other variables that were programmed when the controller was first installed.
Soil moisture sensor controllers (SMS) use two types of control strategies: by-pass and on-demand.
Bypass SMS Controllers
These are set like traditional timed controllers, with watering schedules, start times, and duration. However, the system will stop the next scheduled irrigation when it senses there’s enough moisture in the soil. Most of these types of controllers are added to an existing time clock, and many of these only include one soil moisture sensor. In this case the sensor should be buried in the driest irrigation zone, and the run times for the other zones should be adjusted to prevent over-watering. Some controllers, though, have multiple sensors, one for each irrigation zone.
On-Demand SMS Controllers
These controllers aren’t programmed for duration, only for start times and days of the week for watering. They initiate irrigation at a user-set low soil moisture threshold, and terminate irrigation at a high threshold.
Soil moisture-based controllers can be retrofitted on existing irrigation systems. Many manufacturers also make soil moisture sensors that can retrofit to existing systems and interface with the current controller already on-site.
For advice on what type of controller is best for you, and for repairs and maintenance of your sprinkler system, call South Austin Irrigation at (512) 534-7449 or fill out our service request form.
