Hopefully, a long runner...
I just finished the digital clock. In it, I combined a ESP8266 NODEMCU, Rechargeable Lithium battery based RTC, DH11 Temp/Pressure Sensor, and PCF8574 DIO Expansion board.
The code was a bear. I wanted to be able to specify a timezone and DST time for the clock. On Startup, the ESP8266 starts in AP mode. You Connect to the DigitalCLock SSID, supply a SSID with internet access and password, and the TimeZone.H string from DAYLIGHT STANDARD and DAYLIGHT SVINGS time. The clock displays time in that specified timezone..
Once a week, the clock syncs the RTC to the internet, to keep the clock accurate. Not seconds or milliseconds, though, just the nearest minute.... a normal, everyday clock
On power out, the clock reloads the time from the RTC, then syncs to the internet to update.
I added a PCF8574 DIO Extender to add a few LED's. Yellow lights up the upper left during daytime, Blue lights up the lower right at night, and a Red LED indicates when the clock needs to be connected with via AP mode to enter an SSID and Password via WIFI interface An external Reset button restarts the entire WiFi Configuration Setup when pressed.
The PCB board design is about as far as I can go with milling a PCB onto a 70mX100mm single clad... I've got a couple/few VIA's on this one on the top....Still it did turn out pretty good. No SMD stuff here... just good old TH....
Just for anyone who is interested, I've attached the Arduino Code, Gerber files for the PCB board, STL files for the 3D Printer pieces, and G Code used to drill the holes and cut the traces in the PCB. I enjoyed this project!
All Project Files: