# Water Sensors

Having a robust portfolio of the sensor for measuring soil and water characteristics is a need found by many research communities. In this direction, we include a collection of sensors that despite not being low cost or open source, they are still affordable and well documented when compared to other commercial solution. From a cost perspective, they are not aimed at being massively deployed but instead used individually in a specific site for specific needs.

The sensors selected are from Atlas Scientific, a New York-based company that converts devices that were originally designed to be used by humans into devices that are specifically designed to be used by robots. As already mentioned the sensors are not entirely open source as the other sensors documented on this section. However, they are modular and exceptionally well documented by the manufacturer. That includes documentation on how to install, calibrate and integrate them with additional existing hardware. In this direction, we developed a full library for the SCK to support the sensors via the Auxiliary sensor connector. We also developed a Python script to simplify the calibration process of the sensors. As the sensors can be configured in different ways, we do not provide a full step-by-step guide. Instead, we refer to the documentation on the project's repository.

The setup is built out of the following main components:

• Atlas Scientific Sensor Probe: The physical probe we will insert on to the soil (or water).
• Atlas Scientific EZO Circuit: The driver that will read the analog signal coming from the Sensor Probe and turn it into a meaningful numeric value by applying the different calibration operations.
• Whitebox Labs Tentacle T3: The motherboard that puts everything together and hosts up to 3 Atlas Scientific Probes. It connects to the SCK via the Aux sensor connector. This boards can be chained to support more sensors, but this is not documented at the moment.
• SEEED Grove - 4 pin Female Jumper to Grove 4 pin Conversion
• Cable needs to be used to connect the board to the SCK.

Different sensor probes can be selected for different needs. For example the setup shown above is designed for soil measurements and includes Atlas Scientific temperature, conductivity and PH probes. It also consists of a Chirp Moisture Sensor as described in the above section. As an additional example the setup in the figure below is designed for water monitoring on aquaponics systems and includes Atlas Scientific probes for PH, conductivity and dissolved oxygen.

ID Name Description Unit Measurement Description
10 Battery Custom Circuit % battery The SCK remaining battery level in percentage.
13 HPP828E031 Humidity % humidity Relative humidity is a measure of the amount of moisture in the air relative to the total amount of moisture the air can hold. For instance
12 HPP828E031 Temperature ºC air temperature Air temperature is a measure of how hot or cold the air is. It is the most commonly measured weather parameter. Air temperature is dependent on the amount and strength of the sunlight hitting the earth
14 BH1730FVC Digital Ambient Light Sensor Lux light Lux is a measure of how much light is spread over a given area. A full moon clear night is around 1 lux
15 MiCS-4514 NO2 kOhm/ppm no2 Nitrogen dioxide is a toxic gas. It is a pollutant in some urban areas due the excess air required for complete combustion of fuels introduces nitrogen into the combustion of internal combustion engines (cars
16 MiCS-4514 CO kOhm/ppm co Carbon monoxide is a colorless
29 MEMS Mic MEMS microphone with envelope follower sound pressure sensor (noise) dBC noise dB's measure sound pressure difference between the average local pressure and the pressure in the sound wave. A quiet library is below 40dB
42 DS18B20 Submergible Water Temperature sensor °C water temperature Water temperature is a measure of how hot or cold the water is.
46 AS EZO Specific Gravity Atlas Scientific EZO™ Specific Gravity SG specific gravity The density of a substance to the density of a reference substance.
49 AS EZO Oxygen Saturation Atlas Scientific EZO™ Oxygen Saturation % oxygen saturation Relative measure of the concentration of oxygen that is dissolved in Water
43 AS EZO PH Atlas Scientific EZO™ pH PH pH pH is a numeric scale used to specify the acidity or basicity of an aqueous solution.
48 AS EZO Dissolved Oxygen Atlas Scientific EZO™ Dissolved Oxygen mg/L dissolved oxygen Absolute measure of the concentration of oxygen that is dissolved in Water
45 AS EZO Electrical Conductivity Atlas Scientific EZO™ Electrical Conductivity µS/cm electrical conductivity How strongly a given material opposes the flow of electric current.

### Atlas Scientific Carrier board boardLink

We recommend using Whitebox Labs Tentacle T3 that hosts up to 3 Atlas Scientific Probes. It connects to the SCK via the Aux sensor connector. This boards can be chained to support more sensors, but this is not documented at the moment. However, before it existed we designed a custom board in collaboration in with Aquapiooners.

There is not an standard enclosure and in many cases a simple IP65 box could work. However, in collaboration in with Aquapiooners we designed the custom enclosure below.

The enclosure of the monitoring board and the smart citizen have been designed on Onshape, you can either download the STL files or copy the project to your onshape account and modify them as you wish : The Onshape documents of the monitoring case

We have also designed a probe holder if you want to hold your probes on the side of you fish tank : The Onshape document of the probes holder

The Smart Citizen firmware has the support for the monitoring board built-in. To enable the sensors you just need to plug you board to the Smart Citizen kit aux port and reboot the Smart Citizen Kit and the sensors will be handled by the board. However, you will need to register your device again using the Advanced Kit Selection. At the moment the closest Kit Blueprint will be #22 BioPV Kit. You can request in the forum for a custom blueprint with the specific sensors you are using.

## How to calibrate the sensorsLink

In order to calibrate the sensors you will need to use the USB Shell.

format of the command line

control atlas ph com,[point],[pH value at current temperature]


The pH value at current temperature can be found on the reference table on the calibration solution bottle. If the current temperature is not on it, use the closest value.

First start a serial communication with the Smart Citizen Kit with screen or pio device monitoror even the serial monitor of the Arduino IDE.

Order of the calibration :

1. mid point
2. low point
3. high point

important ! : Always calibrate the mid point first because it calibration erase all the previous calibration done.

Always clean the probe with distilled water between each calibration

• The mid point calibration : Put the sensor in the pH 7 calibration solution and run the command below :
control atlas ph com cal,mid,[value of pH at current temperature]


example at 30°C :

control atlas ph com cal,mid,6.99

• The low point calibration : Put the sensor in the pH 4 calibration solution and run the command below :
control atlas ph com cal,low,[value of pH at current temperature]

• The high point calibration : Put the sensor in the pH 10 calibration solution and run the command below :
control atlas ph com cal,high,[value of pH at current temperature]


Note : (not tested) If your calibration solutions are not 4, 7 and 10, you can still use them and replace [value of pH at current temperature] by your values.

Order of the calibration :

1. dry point
2. high point

3. The dry point calibration : Check that the sensor is dry and run the command below :

control atlas ec com cal,dry

• The high point calibration : Put the sensor in the high point calibration solution (12,880 µS/cm) and run the command below :
control atlas ec com cal,high,[value of EC at current temperature]


example at 30°C :

control atlas ec set cal,high,14,120


Important ! : Do not forget the , between the hundreds and the thousands or else the calibration will not occur !

Note : (not tested) If your calibration solution is not 12880 µS/cm, you can use another one and replace [value of pH at current temperature] by your value of electroconducivity.

Order of the calibration

1. dry point
2. 0 mg/L point (optional)

3. The dry point calibration : Check that the sensor is dry and run the command below :

control atlas do com cal

• The 0mg/L point calibration : Put the sensor in the 0mg/L calibration solution and run the command below :
control atlas do com cal,0