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wall clock with LED clock add-on The LED clock is an add-on for round wall clocks. The purpose is to have LEDs on the circumference of the clock to show the progress of the time using coloured light.


For that you will need:

  • WS2812b RGB LEDs strip (long enough to go around the clock)
  • development board with a STM32F103 micro-controller and 32.768 kHz oscillator for the Real Time Clock (such as the blue pill), or external RTC module such as the I2C DS1307 (only supported in the old firmware)
  • coin cell battery to keep the RTC running (optional)
  • GL5528 photo-resistor to adjust the LED brightness (optional)
  • DCF77 to automatically update the time (recommended)

More details about the project can be found in the README.
The code for the micro-controller is available on git. It includes the script to compile the code, flash the firmware, and generate the source documentation is included.
A release with sources, compiled firmware, and documentation is available here.

Here I will only put picture to show how it looks like.


LED clock add-on Here is the LED clock add-on:

  1. blue pill development board with STM32F103 micro-controller
  2. tiny RTC I2C module with Maxim DS1307 RTC IC (not used in the end)
  3. CR2032 coin cell battery (to keep the internal RTC running)
  4. DCF77 receiver module (salvaged from a radio clock)
  5. USB to power board and LEDs
  6. ST-Link V2 (clone) to program the micro-controller
  7. USB to UART converter to set time and debug
  8. WS2812b LED strip
  9. GL5528 photo-resistor

clock integration

Here how it is integrated in the wall clock:

led_clock.txt · Last modified: 2024/01/07 17:49 by