Mycodo-hyrdoponic-build

A straightforward example of a hardware build to run Mycodo for hydroponics.

Overview

A few years ago we moved and I finally had the space to start messing around with indoor hydroponics to grow fresh food in winter. At first I used the Kratky method because it was cheap, easy and simple. It worked very well but had it's limitations. As things grew they required more and more tending, sometimes I didn't have the time necessary to take care of them properly. This season I wanted to move on to a more advanced ebb and flow setup that could support fruiting crops such as tomatoes.

Part of my day job is designing and building industrial control and building automation systems. Mechanical timers and checking water quality with handheld devices absolutely works but seemed a little low-tech. What I wanted was something easy to assemble with common tools that I could monitor remotely. This is what I wanted to measure and control:

Water Quality
- Temperature
- pH
- EC (electrical conductivity)
- DO (dissolved oxygen)
Air Quality
- Temperature
- Humidity
- CO2
- Vapor Pressure Deficit (calculated)
Control
- Pump 1 - Ebb and Flow (120VAC)
- Pump 2 - Recirculation (120VAC)
- Grow Light 1 (120VAC)
- Grow Light 2 (120VAC)
- Spare 120VAC or 24VDC relays

Hardware

All sensors use the I2C bus. Additional I2C devices can be daisy chained.

Construction

	For the 120VAC and 24DC use 3' (or whatever length you find convenient) extension cords with either the plug or socket removed at one end. Join using Wago connectors. Be sure to use cords and wire that can comfortably carry the load of your devices.
	The Tentacle T3 provides two spare I2C ports. To connect to SCD41 remove one end of the STEMMA QT cable and replace it with suitable 0.1" connector. Be sure to get Vin, GND, SDC and SDA in the right order. Do the same for the EZO DO board but in this case you'll make up 0.1" connections on both sides of the cable.

Enclosure

	Cutouts for the BNC connectors, cords and cables require very precise measurements and special tools. Rather than modify a stock enclosure I designed and 3D printed one. Just about any material will work, I used PLA. If you're using a Pi4 or are stacking more relay boards you will have to modify the geometry. This enclosure prints on a small format Lulzbot Mini.

Software

Originally I'd written my own software in Python. Then I came across Mycodo which has a much nicer and more capable interface so I decided to use that instead.

Support for the Atlas and SCD41 sensors is native in Mycodo. Support for the Sequent relay board is not but fortunately there's a provision. To connect the relay board to Mycodo you'll need to install the drivers and add a shell script.

Enable I2C

sudo apt update & sudo apt upgrade -y
sudo apt install -y build-essential python3-pip python3-dev python3-smbus i2c-tools
sudo raspi-config nonint do_i2c 0
sudo reboot
sudo i2cdetect -y 1

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- 27 -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- 62 63 64 -- 66 -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --

Install the Relay

sudo apt install git -y
# https://github.com/SequentMicrosystems/8relind-rpi/tree/main/python 
git clone https://github.com/SequentMicrosystems/8relind-rpi.git
cd 8relind-rpi/python/8relind/
sudo python3 setup.py install
cd ~/8relind-rpi/
sudo make install
8relind -h
8relind 0 test
cd ~

echo '8relind 0 write $1 $2' >script_on_off.sh
chmod +x script_on_off.sh

From there you can create a Shell On/Off Output in Mycodo like /home/pi/script_on_off.sh 1 on.

Install the Atlas Utilities

Mycodo supports calibration for Atlas sensors. In some cases you'll want to use the Atlas utilities instead. For example, if you're using a K 0.1 or K 10 EC probe for some reason, you'll have to specify that with the Atlas utilities.

git clone https://github.com/AtlasScientific/Raspberry-Pi-sample-code.git
python3 Raspberry-Pi-sample-code/i2c.py

If you are using a Pi4 you may have problems using the Atlas utilities. A workaround for Pi 4 is here.

Gallery

Conclusion

The Pi3 works fine but it's slow. A Pi4 works much better with the caveat you need to figure a way to manage the heat it generates. Unless you're doing aquaponics the DO sensor probably isn't much use and can be elimined. The air temperature, humidity and CO2 sensor is very handy.

Just for fun I've also included a rough sketch of the frame I'm using for this system. When it came time to build that part I considered using t-slotted aluminum frames rather than a standard wire shelf from Uline. Comparing the prices for both, it was a wash so I oped for the more flexible t-slotted design. I've used extruded aluminum many times before from various vendors. Experience is Automation Direct is cheaper and faster than others.

Automation Direct T-Slotted Rails and Components

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