Science fiction movies often portray horticulture in the future, be it terrestrial or aboard spacecraft, with hydroponic gardens overflowing with leafy greens and brightly colored fruit. There is no soil, just clear water that hints at future-people creating a utopia of plant strains untethered from their earthly roots.
This star-faring food production method is not fiction if you forego the polycarbonate tubing, neon accent lights, and gardening robots. For his 2020 Hackaday Prize entry, [AVR] shares how he creates a bed for sixteen plants with parts sourced at a nearby home-improvement store. It may lack the visual pizzaz of the Hollywood versions, but it will grow soil-less crops on a hacker budget.
The starting point for this build is a sturdy wooden base. The PVC tubing and fence parts on top are light, but the water inside them will get heavy, and if you grow large plants, they become surprisingly heavy. Speaking of water, the sub-category of hydroponics this falls under is Nutrient Film Technique, or NFT, which uses a shallow stream of water laden with all the nutrients for plant growth. The square fence posts provide a flat top for mounting mesh cups where the plants grow and a flat bottom where the stream continuously flows. A basin and pump keep the plants refreshed and fed until they are ready for harvest.
We’re not exactly what you’d call naturalists here at Hackaday, so to us, the idea that hot pepper seeds need to germinate in hot conditions sounds suspiciously like a joke. The sort of thing somebody might tell you right before they try to sell you an elevator pass, or cram you into a locker. But we don’t think [Dean] would have gone through so much trouble if it wasn’t true. You’re still not going to sell us an elevator pass, though. Not again.
According to [Dean], the Carolina Reaper pepper seeds he bought from Puckerbutt Pepper Company (truly a name you can trust) recommend that they be germinated at a temperature between 80 and 85 degrees Fahrenheit for up to eight weeks. To make sure they were maintained at the optimal temperature for as long as possible, he decided to get a heating pad he could place under the seeds to keep them warm. He just needed some way to make sure the heat only kicked on once the soil temperature fell out of the sweet spot.
To get an accurate reading, [Dean] ended up going with a waterproof K-type thermocouple connected to a SainSmart MAX6675 module that could be buried amongst the seeds. When the soil temperature drops below 82.5 F, it kicks on the heating mat through an IoT Relay by Digital Loggers. He even added in a capacitive soil moisture sensor and a couple of LEDs so he could tell from across the room if he needed to water what he loving refers to as his “Hell Berries”
Looking back through the archives, we see a considerable overlap between hacking and gardening. Since success demands the careful control and monitoring of a myriad of variables, it seems the sort of thing that’s ripe for gloriously over-engineered automation. Especially if you’re trying to get the things to sprout off-world.
The closest some of us at Hackaday get to a green thumb comes when we are painting, so for us and other folks not gifted in the gardening department Bionic Cactus might help. It’s a neatly designed water and light control system, built around an ESP8266. You can control the system through a web interface, setting a schedule for water and light and seeing how much water is left in the reservoir. There is also a soil moisture sensor and it will even email you when it is running low on water. As creator [SamsonKing] notes, if you combine this with a 3D-printed plant pot and light holder, and you’ve got a complete system from growing herbs and spices in the middle of winter.
[SamsonKing] created the system using PlatformIO, a neat open source Internet of Things development platform that means you could probably switch the system over to run on other low-power platforms if you had them lying around. But with an ESP8266 typically costing no more than a few bucks, it’s a neat and low-cost way to keep your plants fed and watered.
Automated gardening has featured many times here at Hackaday, just one of many is this indoor hydroponic lettuce factory.