GLAS Education is experimenting with a water quality monitor anchored in eight feet of water off the shore of Williams Bay. GLAS intern Dylan Hulke and McQuown Scholar Teddy Lampert were major contributors to the project, which they explained at a GLAS presentation. Dylan did much of the electrical engineering, while Teddy focused on creating software to gather and store sensor data.
Ian Woodward, also a McQuown Scholar, contributed much of the 3D design and printing of components used on the monitor. Several other GLAS students also lent their skills to developing the monitor.
The project was financed through an August 2022 grant from the Environmental Education Fund of the Geneva Lake Association. GLAS received the grant in August 2022. GLAS proposes creating buoys to measure water temperature, air temperature, lake turbidity and the lake’s acidity, as well as wave frequency. GLAS staff members Adam McCulloch and Chris Kirby are guiding development of the lake monitor.
Designing and building the monitor took some ingenuity and creativity. Trial and error, followed by more trial and discovery were the keys to its creation.
The lake monitor’s main components are enclosed in a floating waterproof polystyrene sphere, its halves secured with zip ties and a 3-D printed base. The sphere is topped by a clear plastic dome containing solar cells which are used to recharge the monitor’s batteries. Connected to the monitor’s main body are sensors mounted on a 68-inch long, one-inch diameter PVC pipe extending below the waterline.
A smaller white foam plastic float secures the monitor to a vertical buoy owned by the Village of Williams Bay.
“We have a lot of sensors on it right now,” said Teddy. Currently among them are a water temperature sensor, a battery temperature sensor, a battery power sensor, a status light, a clock, a turbidity (water clarity) sensor, a microphone-hydrophone meant to detect boat engine noise, and and a device called a nine-axis absolute orientation sensor intended to measure wave action in the lake. The sensors are connected to programmable electronic microcontrollers called Picos. Data from the sensors is stored on an SD card, a type of removable memory card used to read data, similar to the cards used in digital cameras.
“It not only gives us information about the health of the lake (and) how it is doing, but it also helps us learn how to overcome challenges like building a sensor that has to be deployed on the lake and the challenges that come with that,” Dylan said of the project.
Among those challenges is that the monitor has to remain in the water for up to a month at a time. That means that it has to be able to power itself and be waterproof.
Once or twice a week, GLAS interns and students have to check on the monitor and collect data for downloading and review.
“We get to the [monitor] by canoe, which we get from the Village of Williams Bay. They let us use that every two days at about 2 p.m. or whatever,” Dylan said. “It’s kind of about a 10-minute paddle out there from the boat launch. You can also swim out there.”
The monitor is still a prototype. GLAS students and staff hope to attach more sensors to the monitor and experiment with sensors to develop data on key lake events.
“One of the data points we’re trying to collect is boat wake,” said Teddy. “That’s a bit harder to do because there’s no boat wake sensor you can just buy.”
The experimental wave detector, now on the monitor, is powered by the nine-axis sensor. The onboard hydrophone is a microphone sealed in a plastic container filled with mineral oil.
“The microphone is submerged in mineral oil because the mineral oil is nonconductive, but soundwaves travel through that pretty well when it’s in the water,” Dylan said.
The hydrophone-microphone was tested in a laundry sink in the GLAS Education office. It seemed to work pretty well, Dylan said.
Teddy said it’s hoped that the nine-axis sensor will record a pattern of motion that can be interpreted as a wave. “We’re hoping it (the hydrophone) will hear when a boat goes by,” said Teddy. If the hydrophone detects a boat motor nearby, the motion sensor will be activated, and its data will be stored for later analysis.
In early versions of the lake monitor, the focus was on functionality. Breadboards, sometimes called plugblocks, were used for circuits and connections. It’s useful because it allows components to be removed and replaced easily.
But breadboard connections are not all that secure. “They weren’t the best because connections would just fail for no reason and the wires would get loose and just fall out,” Dylan said. So the electronics were redesigned to reduce the number of breadboards to just one and reduce the number of wires by half. Finally, the breadboards were phased out entirely. Dylan soldered the wires directly to a circuit board.
The monitor’s sensors are powered by a lithium-polymer battery that puts out 3.7 volts at 10,000 milliamps. Testing has shown that this battery can power the sensors for about four days without recharging. The recharging is done over eight hours by the four 5-volt solar cells mounted in the clear plastic dome, Dylan said.
It was a noteable achievement when the students came up with a combination of solar cells that fully charged the monitors’ battery so it would have enough power to operate the monitor’s sensors from sundown to sunrise. It turned out the lake monitor could make it through the night on its own power, Dylan said. “Actually having it survive for a full 24 hours was satisfying,” he said.