Thomas Geers likes palm trees, but they tend to be quite rare in Germany, where he lives. Undeterred by natural environmental condition, he decided to help conserve an endangered species of palm, known as the Chilean honey (or wine) palm — more formally Jubaea chilensis. He purchased 24 seeds for the plant around a year ago, but since their germination time is — in fact — up to a year, he decided to automate the growth process using a Raspberry Pi.
He first bought a mini greenhouse as the basis for his design, then modified it with a plywood housing , which is finished with a weatherproof glaze. Hidden inside the new housing is a Raspberry Pi 3 B+, relay board, and other electronics. The build includes overhead LED lighting, and 12 spray nozzles for automatic irrigation, triggered by a capacitive moisture sensor in the soil. A soil heating mat is controlled with the help of a DS18B20 temperature sensor, and a fan system is available to control humidity.
Results have been quite good, allowing 11 of the 18 seeds planted in the greenhouse to sprout so far. The remaining six sprouting in the seven months before the auto-greenhouse was ready to go.