When most people see plants start to wither, they respond in one of a few different ways. Typically they will pour a little extra water on it or take it out of the sunlight. But when Eduardo Torrealba, recent winner of the Lemelson-Illinois prize for engineering, student co-founder of OSO Technologies and graduate student, found his basil plant in the same condition, he set to work on a very different solution.

Torrealba’s response was a simple-wired device built using off-the-shelf prototyping electronics which could monitor his plant by checking on the moisture levels in the soil. This allowed him to know when he needed to water it. However, he didn’t stop there.

Torrealba’s next step was to find “other people out there who had the same problem as me.” After investigating, he realized this was a significant problem faced by a great number of people. So he said he “grabbed some friends, showed them the idea, pitched them the prototype, they liked it so we started a business, and here we are today.”

Now, according to Plant Link’s Kickstarter page, Plant Link is a system that “monitors the water needs of your lawn, garden or house plants. It alerts you when they need to be watered and can even water them for you.”

The design process started in September 2011 with a very clunky microcontroller connected with a bunch of wires to a computer, Torrealba said. The OSO Technologies team tried a variety of methods to test soil moisture and integrated wireless technology. The team also worked with an industrial design firm on figuring out how the system should look and feel, Torrealba said.

“We’re all engineers,” Torrealba said, “so we needed the design expertise to know how to make something look and feel really good.”

The team also talked to hundreds of potential customers and asked them what kind of features they’d like to see. Then after several iterations of design work, they took the idea to Kickstarter for funding.

Now Plant Link’s Kickstarter has successfully reached its funding goal with 877 backers supplying $96,690 for the project, and the device is currently available for pre-order at Plant Link’s web site, www.myplantlink.com. Torrealba estimated Plant Link will be ready for shipping in early fall. Plant Link devices are assembled by hand, according to the Kickstarter page “using off-the-shelf components (the valve, the microcontroller), combined with some custom designed PCB’s (printed circuit boards) that were ordered from a distributor in the U.S.”

Plant Link makes the moisture measurement using a resistance method to determine the soil water availability. This means that a device called a Link, which is put into the soil, uses two probes in the soil to measure the electrical resistance between them. This is a measurement that changes depending on the amount of water in the soil. The Link must make sure to keep the soil water between the limits of field capacity and permanent wilting point.

Field capacity is when soil cannot hold any more water before gravity draws the water away. If more water were added, the soil would be saturated, and it would start to drain away. When this happens, oxygen, which is necessary for a healthy plant, is displaced from soil pores.

In contrast to field capacity, permanent wilting point is reached when water supplies start to dwindle and water particles cling so tightly to the soil preventing the roots from absorbing any more water. This causes the plant to permanently wilt.

The permanent wilting point subtracted from the field capacity results in total available water. However, even theoretically the total available water is usable by the plant but not all of it is easily accessible. Adding too much water makes it more difficult for the plant to extract the moisture it needs from the soil.

As a result, Plant Link uses another measurement called readily available water or which is the fraction of total available water which can be easily extracted by the plant.

According to Plant Link’s Kickstarter page, “this fraction provides the healthy usable water availability range for the plant and is adjusted for plant type and atmospheric conditions.”

Plant Link then measures the water content in soil to ensure the readily available water is at an optimum level.

The algorithm used by Plant Link monitors the moisture level in the soil between the limits of field capacity and permanent wilting point and determines how much of the water in the soil the plant can use. This algorithm has been in use in agriculture for over 50 years.

Because plants have different watering needs, Plant Link takes into account these needs and allows users to log in to Plant Link’s web site and input data such as plant and soil type manually. Plant Link already has a large database of plants with their watering needs. However, if a user’s plant cannot be found on the database, he or she can let the team know via e-mail.

If the plant is outside, the system also considers local weather patterns in creating the watering schedule. This schedule is updated by every new soil moisture reading which is taken every 5-10 minutes.

The Link then uses the Zigbee system, which is wireless technology like Bluetooth, for the wireless radios that go from the sensors to a base station. The base station connects via Ethernet to a home router which then uploads information to the web site for data monitoring and alerts. Users can log in to the web site at any time to check on their plants or can opt to have emails, push notifications or text messages sent to their phones.

If someone wants to further automate the process, a special device called a Smart Valve can also be used to water the plants when prompted by Plant Link.

Torrealba said, the team behind the technology consists of three mechanical engineers and two electrical engineers. This means the team had little relevant training before their creation of Plant Link. Rather the team had to use their engineering background to adapt and learn what they needed to know.

“The University of Illinois has been great for that, with a fantastic agricultural engineering and plant sciences group that is really world-class,” Torrealba said.

Balancing running a business with the academic pressures of graduate school has not been easy for Torrealba. However, he said, “It’s not impossible and being at a big university with a great group of people makes it more doable than doing it on your own somewhere else.”

When asked about the future of his device, Torrealba has many ideas. “There are a lot of things we’re trying to do in the future, with trying to detect different types of growing conditions such as light, pH, or temperature, and eventually expanding to other markets and building internet connected devices for other applications.”