I always wanted a reliable irrigation controller that I could use in my home garden or even research projects for automatic irrigation scheduling. As an academic, I have used hardware and software from different manufacturers for this purpose, but there was always something missing with commercial systems. The main problem was that most manufactures put electronic and software engineers in charge of such projects and they usually have no clue how agricultural systems work. So the result is not unexpected.
What I've learned over the years is that a reliable automatic irrigation system requires four components:
Reliable soil moisture signal,
Reliable controller,
Reliable automatic irrigation scheduling algorithm, and
Reliable irrigation system.
Unfortunately, any commercial system (for automatic irrigation scheduling) that I have come across so far lacks a few of these components. The main problem, as I mentioned, is usually the lack of expertise in the areas of agriculture and irrigation in teams that develop such systems. This is why we have taken this seriously and our team at DurUntash Lab is comprised of people with backgrounds in electronics, computer and agriculture.
Calendar-based irrigation scheduling using "timers" either wastes a lot of water or does not apply enough. You may even see an irrigation system working when it is raining or the soil is wet. Adding a soil moisture signal to an automatic irrigation system can make a lot of difference IF, and only if, a reliable soil moisture sensor is used. You cannot use just any sensor you find on the Internet and expect results. Some irrigation controllers don't even accept soil moisture signal and the ones that do are usually limited to one sensor brand that is not necessarily a good sensor. As far as we're aware, there are no commercial controllers that work with a "reliable" sensor that is designed and optimized for soilless media like rockwool or coco coir, and rely on a reliable irrigation scheduling "algorithm".
We are proud that our automatic irrigation system is the first and only automatic irrigation system that is reliable in all of the four aspects mentioned above.
We had a blog post a while back about a project carried out about fifteen years ago in our former research group (Irrigation & Drainage Research Group - IDRG). It was about an "automatic drip irrigation system" (proof of concept) we designed and built in our lab. That system was able to irrigate up to four irrigation zones using small water pumps placed in a water tank with a float valve. The tank was connected to tap water.
At the time we were mostly concerned with the number of irrigation zones, rather than the accuracy of irrigation signal. Unfortunately, this is what most irrigation controller manufacturers are also concerned with to date, and the competition is around how many more zones a controller can irrigate. In our most recent project, we developed the SUMERIT irrigation controller to work with our APAS T1 moisture sensor (for both soil and soilless media). The emphasis in the SUMERIT-based automatic irrigation system is accuracy and reliability rather than irrigating more zones.
In this article, I will explain how you can build a complete automatic fertigation system to apply irrigation water and fertilizer (added to a water tank) using the SUMERIT irrigation node and off-the-shelf components. To make the post is easier to follow, I'm going to explain a scenario in which the system is planned and installed in a home garden with raised beds. The concept, however, works in other settings (e.g. grow room, greenhouse, orchard) as well.
List of Materials
Here's a list what you need to get started:
12V to 5v Micro USB converter (optional)
Outdoor enclosure
Large plastic storage container
Disclaimer: I have listed products here that I have personally used to build my own automatic irrigation system with good results. This, however, does not mean that I'm endorsing non-DurUntash products or encouraging you to buy them. Please do your home work and you may find replacements or substitutes that work batter or are cheaper.
Note: If you decided to replace any of the electronic or electrical components with your own, please make sure that they are compatible. Please feel free to contact us if in doubt.
Assembling Control Unit
The wiring diagram for the automatic irrigation system can be found in picture below. The diagram is very straightforward. The red wire is positive (voltage) and the black wire is negative (ground). Please just have this in mind that the SUMERIT control output works like a switch and does not have polarity. This means there is no difference between the two wires that are connected to its control port even though they might have different colors.
Rated voltage and current
The solar panel, rechargeable lead acid battery and irrigation pump are all rated 12V. The solar charger is also designed to work with the same type of solar panel and battery type. The irrigation pump's rated current is 1.1A (13.2W), which can be easily drained from the battery listed here.
I added an inline switch to my design to be able to turn the system off for troubleshooting, and I strongly recommend that you do the same. The rated current and voltage of the switch are 2A and 12V, respectively.
Irrigation controller
As mentioned, the SUMERIT control output comes from a relay, which can handle 60W (up to 2 A @ 30 VDC or ~40 VAC or lower). To be safe, you need to stick with 60% of this rating. If you'd like to turn a water pump with higher rated voltage and current, you might need to use an interface (relay board) that meets your requirements between the controller and your pump.
Control Panel
The SUMERIT irrigation node comes with all the required hardware accessories that allow it be used in a tabletop configuration or two different wall-mount configurations. In my project, I decided to put it inside an outdoor enclosure along with the rest of the components as you can see in picture below. The control panel sits under one of the raised beds in my garden.
Optional 12V to 5V Convertor
The SUMERIT irrigation node comes with a built-in rechargeable Li-ion battery that can power the unit for about 6 months (time varies depending on the model, battery ratings, measurement intervals, and number of sensors) of continuous use with a single charge. Any standard charger providing 100 mA @ 5.0 V with micro USB cable type B can be used to recharge the battery. After finishing the wiring, I decided to add a 12V to 5V micro-USB converter to maintain the SUMERIT battery fully charged at all times. I connected one side of the converter to the battery and plugged the micro-USB cable into the irrigation node USB port.
Soil Moisture Sensors
Two sensor ports to deal with variability
One of the biggest issues with substrate/soil-based irrigation scheduling using moisture sensors is the so called "inconsistent" readings due to non-uniformity within the substrate, and sensor installation errors. The revolutionary aspect of the SUMERIT irrigation node, which distinguishes it from any other controller, is the options it provides in terms of soil moisture feedback. Instead of relying on moisture signal from only one sensor, it allows for averaging moisture readings from two substrate moisture sensors as feedback to effectively deal with the variability.
Installing sensors
In my opinion, this is the trickiest part that most people take it wrong. Sensor installation options generally depend on the sensor, your needs and the type of medium you are using. No installation can be perfect, but there are ways to avoid errors when installing a sensor. The easiest way to make sure things have gone as planned is to install the sensor, water the soil and check the readings. You can tell if the installation is done properly if the readings are within an acceptable range (they’re not too high or too low for a specific soil). Sometimes, you need some level of experience to be able to spot installation errors, so just give yourself time to learn if you are new to using sensors.
I have previously published several blog articles that can help you with moisture sensor installation, minimizing the error, and troubleshooting:
Depending on where (pot, raised bed or soil) I want to monitor moisture, I may use vertical top-down pot installation, horizontal trench/hole sensor installation or both methods (pictures below). The vertical top-down installation proved to be a good method in my raised beds as well. You can find more information on APAS T1 sensor installation method in its user manual.
Water Storage and Irrigation Pump
I used to have only one raised bed and a small water tank when I built my first irrigation system. This summer, I decided to replace the tank with a much larger container because I now have three raised beds and several large plant pots hosting pomegranate and fig trees. The new water storage container can store about 28 gallons (US liquid) of water, which is enough to water the whole garden for several weeks.
The only drawback of having a large storage container is that the wall bulges when full of water. So it's on my to-do list to add some sort of support around the container to avoid a disaster specially during hot summer days! I put the container under one of the raised beds. There is room to add even one more container if needed. Before the pandemic started, I used to travel quite often, and the idea was to have enough water in the tank for the entire period that I was gone.
Irrigation System
For many years, drip irrigation has been my system of choice for irrigating everything ranging from orchards to home garden. The efficiency of drip irrigation system is high. It's also inexpensive, low maintenance and highly flexible. There are many options when it comes to drip irrigation and I'm not going to get into that in this article. There's this irrigation kit that I came across on Amazon about 4 years ago, I bought it and I'm still using it in my garden. I recommend that you use a similar system for the same reasons mentioned above. If you have an existing irrigation system, you just need to find a way to connect it to the pump outlet.
By the way, I have tried both heat gun and hot water to soften the hose before assembling. I strongly recommend using a heat gun (or even a hair dryer) instead of hot water! It's easier to work with and eliminates the danger of burning yourself with hot water.
Irrigation Scheduling Algorithm and Controller Settings
As an irrigation specialist, I know how important irrigation scheduling is. In the past ten years the focus of my academic research has been to develop and evaluate automatic irrigation scheduling algorithms that can automatically and accurately determine when to irrigate and how much water to apply.
The irrigation scheduling algorithm that is used by the SUMERIT node is simple yet robust. The algorithm works independently for the most part, but it needs four important input parameters (settings) from the user at the beginning:
Dry threshold(%). The automatic irrigation scheduling mode requires a "Dry Threshold" to be set. This threshold is used to determine when it's time to irrigate.
Start time (time of day). You also need to set a start time (time of day). Irrigation events will be triggered only at the time of day specified by you.
Run time (minute). If the SUMERIT decides that the soil is too dry, it will run (runtime) for the number of minutes specified by the user. The runtime can be any number between 1 and 1440 minute.
Moisture sensor feedback type. The SUMERIT irrigation node has two sensor ports and you can choose which ports to use. It can be just one or both.
If both ports are reading soil moisture sensors, you can choose to use both for irrigation scheduling. In this case, the SUMERIT node will take the average of moisture readings from both channels. As mentioned, this will increase the accuracy of the moisture signal significantly. If you select only one sensor (channel), only readings from moisture sensor connected to that channel will be the basis for irrigation scheduling. If no channel is selected, the SUMERIT node will turn into a time-based irrigation scheduler that will turn (if auto-irrigation enabled) your water pump on/off at the specified time of day.
You can use the SHUSHAN Mobile app or SHUSHAN CVI Windows application to set these parameters.
Conclusion
That's pretty much it. I might edit this article and add more details over time. So make sure to come back and check the revisit the article. Please go ahead and setup your SUMERIT automatic irrigation system and feel free to contact us if you had any questions.
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