Schematic for ESP-01 web server allowing the wind data to to be presented in real time on a web page. 

Transmit out to Arduino is not used at the moment, but would be a nice option, if you can fit it on the board, so one day Sensor could be configured from web interface.  ArduinoRST goes to the Arduino reset line. RXI is the wind sensor data from the Arduino using a voltage divider (not shown here) (2.2K / 3.3K resistors) to drop the voltage to 3.3V. NPN transistors could be used instead of mosfets Q6 Q7, but they would need bases to be connected to 3.3V via (say) 10K resistors. The mosfets were selected because they use slightly fewer components. Voltage regulator should ideally be a TO220 or similar with a good heat-sinking capability as it has quite a voltage drop, when powered from 12V and the ESP-01 does use 100 mA or so when in WiFi transmission mode. R32 is required to prevent the ESP-01 starting in programming mode. Adding a reset button to ESP-01 is always a useful feature too!

TODO.

• Do a video describing more details of the circuit and how it fits on the car reversing kit PCB.

• Update github project with sub-modules to include required web server libraries.

• Explain how to upload code to ESP-01 etc

Source code for the web server  here:

https://github.com/kwikius/ultrasonic_wind_sensor/blob/master/web_server/web_server.ino