We deployed our water quality sensor in a basin near the East River nearly three weeks ago and it is consistently reporting water quality data. Using circuit and software design by Dylan Sri-Jayantha and components from Adafruit, Atlas Scientific, the device is publishing dissolved oxygen, temperature, salinity and other variables to our water quality dashboard.

floating dissolved oxygen sensor

The dashboard is available on Adafruit I/O on any device with a browser.

water sensor Adafruit I/O

The sensor is located near the site of two combined sewer overflows (CSOs) that may discharge human waste into the water during a heavy rain event. They are each about 100 yards away from the sensor.

combined sewer overflow sensor

Tutorials for construction of the sensors including a parts list, wiring diagram and source code are here (part 1) and here (part 2).

To make the system water ready, we placed added three waterproof glands on the base of a Nanuk 904 case. These ranged in size from PG7 (plastic) to PG5 (brass) and were selected based on the diameter of the sensor cable.
atlas sensors dissolve oxygen

For double protection, we sealed the inside of the case with epoxy.

sensor board - water quality

When launching, we had several concerns.

Power Management

Even with the panel oriented horizontal to the water and shading from trees and steel structures, the system is ably powered. The 9 Watt panel plus V44 44 Watt hour battery has so far kept up with the power demands of the system of 2.2 Watt hours per day through a fairly cloudy early October. We will observe how the system performs through the winter, but it appears we are probably well over-sized on both battery and panel.

System Accuracy

Temperature performance matches what we are seeing in local waterways. The basin is shallower and the sensors are close to the surface so we are seeing one degree fluctuations on a daily basis.

The dissolved oxygen has been fluctuating on a diurnal cycle between a maximum of 5.71 to 2.96 mg/L for the first 23 days. Over the last six days, the readings have fluctuated between 9.4 and 0 mg/L with no clear diurnal cycle. We suspect this is a biofouling issue.

Cellular Signal

The Brooklyn Navy Yard is an industrial area with lots of steel structures that seem to make cellular signals go haywire. The signal in the basin floats between 1 and 2 bars on Verizon. We are seeing the system send signal inconsistently. When the system cannot complete a signal, it goes to sleep for two hours and then tries again.
screenshot adafruit io

In a redesign, we would put a cellular antenna on the outside of the case.

Please reach out to us about your remote monitoring project.

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