When you get the same piece of hardware together with more than a thousand co-workers, there is room for a nice prank. I work at Altran, and everyone was entitled to get a nice word clock. This clock shows the time in words, where separate segments are lit with sets of white LEDs.

When I got the clock, I showed it at the Hackalot hackerspace and they told me they had done a workshop making a WordClock at the hackerspace Bitlair in Amersfoort. Their version was made with color LEDs so there the idea was to transform the WordClock into a color version. I wanted to prank my co-workers by putting this video online:

Here is the final schematic I used:

The Arduino code can be found on GitHub: https://github.com/diystuff/word-clock

This is the shopping list, you can buy it for example at TinyTronics. That is my favorite shop for electronics stuff in Eindhoven. Please support them!

  • 2 x WS2812B Digitale 5050 RGB LED Strip – 60 LEDs 1m
  • 1 x GL5528 LDR lichtgevoelige weerstand
  • 1 x 1000uF 16V Elektrolytische Condensator
  • 1 x Wemos D1 Mini V3 – ESP8266 – CH340
  • 3 x Resistor 10K
  • 1 x RTC (optional)

Here are the revised steps:

  • Carfully remove the filter from the front. You can do that with a normal kitchen knife and a lot of patience.
  • Desolder all the LEDs from the clock
  • Put electrical tape on the place where you want to put the led strips. This is to prevent shortages from the LED strip to the PCB below.
  • Stick the LED strips inside the clock: It’s 3, half 4, ten 3, quarter 7, twenty 6, five 4, minutes 7, to 2, past 4, one 3, three 5, two 4, four 4, five 4, six 3, seven 5, eight 5, nine 4, ten 3, eleven 6, twelve 6, o’clock 7. Watch out for the orientation. DIN starts at the “o’clock” segment and zig zag all the way up to the “ten” segment. DOUT should be connected to a DIN. It should form a complete chain.
  • Connect the power of the LED strips. Attach the capacitor to the power of the led strip. This should provide a steady power supply.
  • Stick the Wemos to the PCB. When you position it wisely, you can drill a hole in the back of the clock. The hole should align with the USB connector of the Wemos.
  • Connect the wires according to the schematic.
  • I will not reveal the details of the RTC because it is not connected yet. It might even be possible to re-use the RTC of the original clock PCB.
  • And NOW power on the clock.
  • Press the [set] button and the time will start blinking. Now set the time to the current time.
  • Press the [set] button and you will see the Eureka screen, followed by the changing colors on the screen.
  • When pressing [up] and [down], you can select the color used.

This is how it looks inside:


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