Automatic plant watering system

thingiverse

Simple, small and versatile plant watering system using Arduino Nano, 0.91" OLED display, miniature water pump and capacitive moisture sensor. It has separate limits for drying and watering. Some plants like stable moisture, which is achieved by setting the limits close to each other. Some plants prefer dry and moist periods, and this is achieved by setting the limits further from each other. Moisture value is based on moving average of 10 measurements taken with 2.4 hours interval, i.e. 10 times per day. After every measurement, pump is operated for 1 seconds to prevent it from jamming. This has been important for reliable operation. Also when the system is started, pump is operated for 2 seconds to show it is functional. Once in day, moisture measurement is compared with drying and watering limit values to determine need for watering cycle or drying cycle. If watering cycle is in progress, once in a day the pump is operated for 100 seconds, which is equivalent for 1.5 liters for my pump. When soil becomes moist enough to exceed moisture limit and stop watering, drying cycle starts. During drying cycle, the programs tests once per day the need to start watering cycle. The display shows the cycle and days elapsed in current cycle, e.g. “Water 5” or “Dry 7”. In my case, watering cycle lasts typically 7 days, during which approximately 10 liters are pumped. The drying cycle lasts typically 10 days. The display shows also the moisture measurement value. There are also error limits to identify and alarm malfunctioning sensor. In the code the parameters are clearly identified for easy customization. The pdf contains parts list, instructions and the sketch. Update 6.3.2021: Updated sketch so that the pumping time can be defined separately for the first day of pumping period.