I am indebted to Kyle Gabriel who has written Mycodo, the open source software described at https://github.com/kizniche/Mycodo. It is specifically written for interfacing sensors, pumps, and various other control systems together in a user friendly interface. It is designed to work on Raspberry Pi computers - I have a Pi 4 for this project.
It was pretty easy to set up. The main “difficulties” encountered were not really difficulties but rather the results of the author’s unfamiliarity with the components of the system, having not often worked with the Raspberry Pi or done much hobby electronics. However, most of the really clever stuff is done behind the scenes and it’s really just a case of plugging things together and configuring things carefully so that the various methods of communicating data between devices work properly.
In the current system, most of the devices (pH, EC, and temperature sensors, and the 4 dosing pumps) use the I2C communication protocol that allows multiple devices to be connected in parallel and still be addressed separately, and read / controlled independently by the system. All of these devices arrived set to use a different protocol (UART), and so had to be configured to change the protocol, a process that involved shorting out certain pins whilst powering the devices on. Once this was done, the devices could be wired up to the Raspberry Pi via breadboards and jumper wires with no real difficulties, even for a careful beginner.
The temperature / humidity sensor for the room was wired up to use the simple UART protocol, and the CO2 sensor data was connected into a GPIO pin (general purpose in/out) on the Pi.
The only other thing connected at the moment is a basic Pi camera which is set up to take a time lapse image every 2 hours. It is also very useful for keeping an eye on the system whilst I am not at home - i can take a still image at any time via the Mycodo dashboard, as I have set up port forwarding from my local wifi router such that I can connect to the raspberry pi via wifi by accessing my router’s public IP address from any web browser.
A final couple of additions I made allow me to control the system remotely. I bought two “smart” plugs that are linked to an Amazon account and can be switched on and off from anywhere with an internet connection. One provides power to the lights and water pump, and one powers the raspberry pi. This setup means that if i suspect a problem with the system whilst I am away from home, I can simply shut the whole thing down until I get back home to investigate further. I have the system set up to email me if the pH or EC goes out of the expected range, and I can check it whenever I want anyway, so I think it is a sound system for running even when I am not at home. This method of remote checking was tested over Christmas and I found it worked really well, though nothing actually went wrong that required a proper test…!
A final benefit of these smart plugs is that they can monitor the electrical power usage of the components that run from them. Notwithstanding the fact that the plugs themselves also consume some small amount of energy, I can use this information to help gauge the “eco credentials” of the whole idea, once I have run more experiments and had the system running for a few months.
I am somewhat worried that the power usage may be hard to justify with respect to simply buying the equivalent herbs in a supermarket, but this remains to be seen. I could switch my energy supplier to one which supplies renewable energy only, but this is still inefficient when compared with using direct sunlight. However, in my current flat, with limited space, in a dark Scottish winter, this is far from an easy way to run things…
