This a project is to make a device that checks up to six plants moisture levels and returns the value as a percent. I used generic soil sensors and soldered them directly to the PCB board and then the probs connect on the top. It connects to Cayenne by a ESP8266-01 chip & the main board is a Arduino Pro Mini. It energizes the soil sensor board, takes the analog reading, and then turns the board back off. This helps quite a bit in slowing corrosion of the probes. All the data is sent to Cayenne so it can be viewed on a dashboard.
I also designed simple case to hold it which I included.