My plants were home alone for a month while I was visiting Israel
This is how they stayed alive.
Major cities in China are extremely polluted. You can find yourself staying indoors for days with closed windows, hence there is a need for many plants in the house. At the beginning of 2017 Katie and I moved to China with our 8 months old daughter, Nina. Katie had found an old research made by NASA, it examines a verity of plants with air purification abilities.
As soon as we settled in our new apartment we bought a total of 14 plants. We have 5 different kinds, each one with its unique abilities.
Later on at the summer we had planned a month long vacation in Israel, but had no solution regarding watering our plants. I decided to solve the problem by make another project. I planned a system that will sample humidity of the plants' dirt and provide them water accordingly. Sounds quite simple, but turned out to be a complex project involving long term examinations and many tests. I made an electronic circuit containing a relay for a water pump and 5 humidity sensors, one for each type of plant (assuming similar water consumption for plants of same type).
For more than two weeks I monitored the humidity of 5 plants as I was watering and them regularly, recording the humidity readings and documenting the amounts of water I gave. I made graphs showing the humidity change as the days go by and found the ranges in which they vary. In the graph below you can clearly see the humidity change with time, the drastic changes occur when I watered the plants. This information was esential and I later implemented in my final program.
Next steps were making the physical structure and mechanism. Since water is also polluted here, we are using mineral drinking water and have many 3 litter bottles. I decided to reuse them and designed a wooden structure using 5 bottles as funnels. Each funnel would direct water for plants of the same type. At the top I mounted a servo motor with an arm to direct a water hose to each funnel. Each funnel cap was connected to a hoses that directed the water to the plants.
Tow days before we left I gathered all of our plants and placed them around the machine. I used the data gathered earlier to calculate how many litters of water the plants will consume and then needed to find a way to store more than 50 litters of water. I decided again to use the 3 liter water bottles. I connecting 16 of them together and added another 20 liter bottle just to be safe.
I used an Arduino mini and wrote an embedded program to read the humidity sensors and control the water pump, and servo. The program has three modes: 1. manual mode lets me water each set of plants on command 2. Interval mode will water the plants automatically once every few days according to a plan I wrote in advance 3. autonomous mode samples humidity throughout the day and water the plants when needed. I wrote a simple protocol to control the machine through the serial monitor and enable me to control it from my phone in Israel.
I also placed a camera for monitoring and capturing videos. Two days after we arrived to Israel I got the first video of the machine in action.