For quite a while I had been longing to measure the waterlevel in my well.
The first attempt with a HC-SR04 failed due to distance (4 meter deep well) and problems of how to mount it in the well. Then I came across the JSN-SR04 sensor. It's all running on an esp2866 (I found it to have better wifi than the esp32). Several parts re-used from old projects. Added small solar panel to keep it all self contained. Data is sent to homeassistant (mqtt) and a bit of log/debug data to syslog.
Due to circumstances had it been lying on my desk quite a while, but finally, today I was able to install it!
I screwed a drainpipe cap to the lid of the well and mounted the sensor in another. A simple pipe connector in between works like a charm.
I use deep-sleep. At the moment it measures 3x in the hour. The esp however is on a pcb with connectors. The rst-d0 link is on the pcb as is the us module (also connectors) and the power (also connector) I can just pull the esp from the socket to re-program.