martin-vi / elfema-ntp

Elfema NTP Clock

I saved this clock from the trash. This is a clock manufactured from the GDR company called Elfema. It's a slave clock from a clock network system. Since the original master clock is too bulky, here is a updated version with new nifty features:

• NTP based time synchronisation
• HTTP-Interface
• automatic daylight saving time
• 12V power supply

Hardware

Used components:

• ESP-03 (ESP8266)
• 2N3906 Transitor
• CD40109 Low-to-High Voltage Level Shifter
• 1N4001 Diode
• SZ508 Zener Diode
• BY133 Diode
• ‥ some resistors and a capacitor

Equipment:

• USB-to-Serial Adapter for programming (e.g. CP2102)

Schematic

Scan of the sketched schematic.

Images

The Elfema clock front.

The soldered board with the ESP-03 board (ESP8266) on the backside.

Build

Install platformio and checkout the repository.

$ echo -e "myssid\tsupersecretwifipassword" > secret
$ source env/activate               # set $PLATFORMIO_BUILD_FLAGS
$ platformio run --target upload    # build and upload to ESP8266

Use

Power up the clock and wait some seconds. The clock indicates complete network and time setup by moving the minute clockhand. Now tell the clock it's current clockhand settings.

# determine the ip adress, here it's 192.168.42.106
$ curl "192.168.42.106/time"  # check the clock time
ntp time and date: 23:46:11 27.10.2016
# read the clockhands
$ curl "192.168.42.106/set?H=18&M=24"
ok got it!

After that the clock will set itself to the current time. Please do not use this in public / unsecure network environment. Otherwise someone is going to mess up the time and clock.

Ideas

• add a spare AM2302 sensor on GPIO16
• Secure HTTP interface with challenge-response authentication
• OTA Updates
• build some nifty mobile app (apache cordova?)