Hydroponic Beginnings: The Evolution of My First Prototype and the Surprising Lessons Learned
How it all started...
First there was a proof of concept to validate that the horticulture LED lights could maintain or grow a set of strawberry plants at home, without much help of natural sunlight. The lights themselves were a kit from Wurth Elektronik with connectivity to an app that can control de amount of color of each channel, there are four channels: White, Hyper Red, Far Red, and Deep Blue.
Here lies the first learning discovery in my search for the at home hydroponic system: plants have different color needs throughout their growth stages. As mentioned in the Weekand's website article about the light spectrum, blue light encourages root growth (ideal for starting seedlings); red light encourages flowering and fruit production; green and yellow are mostly reflected but some plants do use it in the photosynthesis process, so it is good to cover the entire visible range. See below the wavelength distribution of the usual color LEDs vs the horticulture ones.
By Wurth Elektronik. (Source)
After testing the LED kit for a couple of weeks, I noticed that the plants weren't too happy, but I didn't know what the problem was. Maybe light intensity? soil humidity? nutrients? There were a lot of variables I still didn't know about and too much variability in the daily routine. So I decided to start the V1 prototype.
Solaris V1 included the newly learned fact about the color variation in the form of a simple PCB with three channels, white, deep blue, and hyper red. I did not include far red as it didn't seem to make much difference, but more on that later.
Version 1 of the at home hydroponics prototype system started with the following components:
- 3-channel LED PCB
- 24V 4A power supply
- Arduino Uno R4
- NFT (Nutrient Film Technique) watering system
- Temperature, light intensity and color distribution sensors
- Small rack to mount everything
I designed a custom 3-channel LED light that had PWM control, for any microcontroller. I picked the newest Arduino as it had WiFi connectivity and worked out of the box with Arduino IoT. For the PCB design I used Altium Designer.
This first design had a few issues. There was no big copper layer sink for heat to spread correctly, traces were too small, and there were not enough LEDs in one board to supply enough light. In the V2 prototype, I fix this.
For the watering techniques, there are several, all with advantages, disadvantages and complexities. I figured that the NFT technique was the most appropriate and moderately complex to start with. Here are all the methods:
And this is how the V1 prototype looked like.
A pump was located in the white tank below, that re-circulated the water+nutrients mixture around the system. With the help of 3D printing I was able to prototype couplings and fixtures for the tubes that carried the water.
Then here comes the second learning discovery: nutrients and pH are very important. For hydroponics you should generally aim for a pH between 5.5 and 6.5. Which in given by three main three main elements, nitrogen, phosphorus, and potassium. You also need to take care of the nutrient concentration and system maintenance (flushing and cleaning). If you take care of each of these factors, you avoid problems like yellowing, weak stems, leaf burn, algae and mold, buildups, and more.
Luckily there are a lot of resources online, pre-made nutrient mixtures, pH measuring kits, and nutrient concentration measuring devices. So the guessing game gets reduced, but a challenge is definitely understanding your plants and identifying what the issue is.
Once the system was running correctly, the next challenge I faced was when trying to germinate some lettuce seedlings again...
So here comes the third learning discovery: humidity has a huge impact on seed-starting. Your seeds will have different watering requirements depending on where you live, and the kind of seed. If you live in a very dry place, you will need to water them more frequently and place a humidity cover on top. If you live in a humid place (by the coast or big body of water), watering is less rigorous and you can remove the cover.
After trying several times to grow seeds again and finally achieving a good result, lettuce was thriving!
But after some time without trimming and maintaining the leafs, it gets out of control and some plants get better light and nutrients than others. It is crucial to remove the leafs or define a cycle for seed-starting and a complete system reset (cleaning tank, pump, water channels, pots, etc). If not, it all gets out of control quickly as the plants have resources readily available.
So far, that was the progress of the first version of the at home hydroponics project. There were a lot of new learning discoveries and frustrating times, but it has been mostly fun and enriching to combine engineering with horticulture to create a mini home farm. There is still a lot more to improve and learn.
Stay tuned for the V2 prototype!