Update the add on board with ESP-01. Once added to the board Initially I found that ESP-01 had difficulty connecting to the network. I suspect that it is due to noise on the hacked PCB , since connection works fine, if the Arduino is held in reset.  That being the case, I solved the problem by connecting the ESP-01 GPI0 to the Arduino RST input ( via suitable level shift). Now When ESP-01 wishes to connect , it puts Arduino in reset and takes Arduino out of reset once connected. This works well as a solution on the demo board. Once connected the Wifi is smart enough to avoid the noise frequencies and the connection seems to be robust enough for testing and demonstrating.

https://github.com/kwikius/ultrasonic_wind_sensor/blob/master/web_server/web_server.ino#L105

TODO: Provide circuit details for ESP-01 and a video of the updated board