Software apps and online services
Mimosas are some of the most sensitive plants. If you left one without water for a week (whether because of holiday or you simply forget it), you will be sorry!
There are many Arduino projects dedicated to this objective, but it depends on what you want:
- Receive a warning (alarm sound, SMS, etc.) and you must go water the plant?
- The device is monitoring the plant, pouring water when needed. You just visit it from time to time, and refill the water container every 1..2 months.
We selected the second option.
Full detail at: https://sites.google.com/site/pre2arduino/
This is the central unit, which displays the mimosa emoticon :) :| or :( , humidity (%), days and hours since last water pumping. You can use another display of course. This one is reused from another board (Pololu A-Star Prime).
The moisture sensor is in fact from here: BangGood. It is a resistivity based sensor, which is not corroded as others write in Hackster projects. If you power-it on for only several milliseconds each time, just enough to read the humidity, it works fine. The one I show, worked for months, without any sign of corrosion. Just use the attached software. However other issues could occur: wet mud attaching to the sensor, thus indicating a different local humidity from the rest of the pot! If the sensor is too far from the water tube, the readings will have a large delay: time for water to diffuse in the pot!! Put it sufficiently close to the water tube to stop the pump, before there is too much water in the pot !! Change the humidity threshold in the software, according to your plant requirements. This one pumps water below 95% humidity, for several seconds. Then, if the indicated humidity did not surpass 95%, a new quantity of water is pumped. This method allows for water diffusion in the pot.
As micro-controller, we suggest the AtTiny85, it has the necessary I-O pins, just enough for the purpose (and cheaper than other Micro Controllers!).
The whole device (pump included) is continuously powered from a 220V power adapter giving 9V/ 0.5A. In case of a power failure, (lasting less than a few days, or else the plant will dry out!), it is not a problem. The system will restart, reading the humidity and pump water if needed, then will reset the hours and days counter.
Powering the pump is done by a Mosfet module, but this can be done by other means too, (e.g. a relay). The display can be any other with I2C interface. This one has a parallel interface, so a I2C adapter was needed (AtTiny85 has only 6 pins!!) .