Add Dissolved Oxygen To The WiFi Hydroponics Kit

This tutorial will demonstrate how to add the EZO D.O circuit and probe to the WiFi Hydroponics Kit from Atlas Scientific.

It is assumed that the user has the wifi hydroponics kit working and is now ready to add dissolved oxygen.

WARNINGS:

• Atlas Scientific does not make consumer electronics. This equipment is intended for electrical engineers. If you are not familiar with electrical engineering or embedded systems programming, this product may not be for you.
• This device (WiFi Hydroponics Meter) was developed and tested using a Windows computer. It was not tested on Mac, Atlas Scientific does not know if these instructions are compatible with a Mac system.

Step 1: Create a field for dissolved oxygen data

Go to your channel in ThingSpeak.

Select Channel Settings and click on the checkbox to enable field 4

Fill in the box for field 4. For reference, we entered DO (mg/L)

Scroll to the bottom of the page and click Save Channel

Step 2: Set D.O circuit to I2C

The simplest way to set the D.O circuit to I2C mode is with the I2C Toggler.

1. Set the switch on the toggler towards DO

2. Insert the D.O circuit

3. Plug the I2C toggler into USB port/cable

4. Press and hold the button for about 1 second

5. Release after color change: Green = UART, Blue = I2C

Step 3: Add D.O circuit and probe to meter

After you have put the circuit in I2C mode, insert it into the AUX port of the hydroponics meter and connect the probe to the corresponding SMA connector.

Step 4: Flash the meter with the correct code

In the Arduino IDE go to File> Examples> EZO_I2C_lib-master> Examples> IOT_kits>hydroponics_kit_with_DO

Add your Wi-Fi name, Wi-Fi password, ThingSpeak Channel ID, and ThingSpeak Write API Key to the code.

Set your IDE to the correct target CPU: Tools > Board > Adafruit Esp32Feather

Set the correct port where the CPU is connected. For example, it is connected to COM107: Tools > Port > COM107

Compile and upload the code.

Step 5: Calibrate D.O probe

Atlas Scientific created a list of calibration commands that are built into the library. Type in help in the serial monitor to see the list of commands.

Send the command poll. This will let you see the readings once per second, and it will stop uploading to ThingSpeak while you calibrate.

Onto calibrating the dissolved oxygen probe. The EZO D.O circuit has a flexible protocol, allowing for a single point or dual point calibration.

Single Point Calibration

Let the dissolved oxygen probe sit, exposed to air until the readings stabilize (small movement from one reading to the next is normal).

Once the readings have stabilized, issue the command do:cal

Dual Point Calibration (optional)

Only perform this calibration if you require readings below 1.0mg/L.

After you have finished the single-point calibration, place the probe into the zero dissolved oxygen solution and stir the probe around to remove trapped air. Let the probe sit in the solution until the readings stabilize (small movement from one reading to the next is normal).

Once the readings have stabilized, issue the command do:cal, 0

Step 6: Upload to ThingSpeak

To resume taking a reading every 15 seconds and uploading it to ThingSpeak issue the datalog command.