I hope everyone is well. I've searching this question for a long time but I couldn't find an answer. I've been working on my own smart pots for plants for a long time and I've tried so many soil moisture sensors. Now I want to make my own sensor. In the internet I found DIY basic soil moisture sensors but I want to make with analog output and readable from Arduino Uno. So what are your suggestions? Where should I start?
Thanks in advance.
Two nails and a resistor would be a start.
Just don't expect it to be very reliable or so, but that accounts for most such sensors.
You should copy the "Capacitive Soil Moisture Sensor V1.2" from DFRobot (that many other copy and sell). Its MUCH better than all the resistive tests, doesnt degrade, no direct contact to soil etc.
Also it really doesnt need a lot of parts. I guess someone already reverse engineered it somewhere on the web. If not: Its really easy. Be the first to document it.