I think the comments you make are good. I do have a question about the removing the regulator. I assume you mean the 5V to 3.3V regulator. I connect to the 5V and I see lot of variation in moisture readings due to the variation in the output of the power supply (solar panel/stepdown). I have a calibration routine for that. The voltage can go as high as 4.2V, which I believe may be bad if I connect the power supply to 3.3V. Of course, this is not a concern if using two 1.5V batteries. With batteries, the moisture reading would be more consistent over a day. Lot of advantages there. I just don't like changing batteries and I really hate it when they leak. I have every reason to believe that my power supply will last 10 years and I am fortunate to live in a place with consistent sunshine :) . Someone replicating my project will have to take this into consideration. My design easily accommodates a different power supply. And my power supply could be used in other projects. Resistive vs Capacitive sensor. I'm glad you report good results. This gives people options. Water moisture: I've had good experience with "spraying" the Arduino with clear electronic coating and sealing the enclosure with liquid tape. -OSD

@Serg2055 as the name says, openhardware.io is for open hardware. You are allowed to sell PCB units, partially or fully soldered boards, but selling source is not an acceptable option. Please include readable schematic and source of your boards or at least gerbers or bom. For all your boards posted on openhardware.io. Thank you !

@schif Hello, Thanx for you comment. Yes you can use it but use a ceramic capacitor ;)

hello! can you advice how flash this fw in arduino ide with avr isp? not work with atmega without crystal yet :(