A real word clock with 24 LEDs controlled by a Raspberry Pi Zero W (RPi) in Python.
Reduce the additional components to an absolute minimum. No additional PCBs or parts (shift register, port expander, driver, resistors, …) are needed.
Just glue 24 strong LEDs behind/below acrylic plates with the words and wire them directly to the RPi pads. The soldering is reduced to cables between LEDs and RPi. The clock can be powered over a Micro-USB cable from a mobile phone power supply.
- The transitions between time values are blended via PWM for all LEDs.
- The current time is received via NTP over WiFi.
- Two free pins for additional gadgets (I²C, GPIO).
In the German language it is common to say „halb zwölf“ (translated: „half twelve“ or „half of twelve“ = 11:30h).
In a little area in the south of Germany – Franconia – you can hear people saying consequently „viertel zwölf“ („quarter twelve“ = 11:15h) and „dreiviertel zwölf“ („three-quarter twelve“ = 11:45h). In the other parts of Germany the Franconians often are not understood.
It is also common to say „fife to twelve“ (11:55h) and „fife past twelve“ (12:05h). This is equal in German and English.
In final consequence it is logical to say „zwei vor dreiviertel zwölf“ („two to tree-quarter twelve“ = 12:42h = 23:42h)
The clock is using this Franconian schema/wording to show the time with 24 elements/LEDs.
Most other so called “word clocks” are using illuminated characters and get a time in a resolution of 5 minutes. The Franconian clock uses 24 complete words and gets a time resolution of 1 minute!
- Numbers 1 to 7 for minutes
- “to” and “past”
- “quarter”, “half” and “three-quarter” (the “quarter” is shared)
- Numbers 1 to 12 for hours
Reducing the electronic components to the RPi, the LEDs and the wires between them, you can concentrate on form and design.
Using high luminance LEDs with a max. of 3.1 volts. Any color you like.
The current to the LEDs is limited by the RPi to 8 mA per GPIO via software. Possible values are 2, 4, 8, 16 (higher than 8 is not recommended). The usual resistor in line of the LED is not needed!
The RPi can be powered over a Micro-USB cable. Use a mobile phone power supply (for USB) or a nearby PC/server with USB.
The typical current at the 5 volts line is about 100 mA with peaks up to 300 mA when WiFi fires.
Following the rules of the wording you are free to sculpt, form and place the illuminated words with any material and technique.
To use low voltage bulbs (5...24V), you can add 3 driver ICs like the ULN2803 directly to the RPi without a level shifter.
Pins for I²C are left free for additional IoT gadgets for e.g. temperature, humidity, luminosity, presence, notification...
Pins 7 to 40 should be used for the clock LEDs.
Pins 1 to 6 are free for optional I²C devices and other GPIO stuff.
Four groups to set the time as text:
E.g.: "| drei | vor | drei.viertel | zwölf |" (23:42h)
| Pin | engl. | ger. |
|---|---|---|
| M1 | one | eins |
| M2 | two | zwei |
| M3 | three | drei |
| M4 | four | vier |
| M5 | five | fünf |
| M6 | six | sechs |
| M7 | seven | sieben |
| Pin | engl. | ger. |
|---|---|---|
| TO | to | vor |
| PAST | past | nach |
| Pin | engl. | ger. |
|---|---|---|
| Q1 | ...quarter | ...viertel |
| Q2 | half | halb |
| Q3 | three... | drei... |
| Pin | engl. | ger. |
|---|---|---|
| H1 | one | eins |
| H2 | two | zwei |
| H3 | three | drei |
| H4 | four | vier |
| H5 | five | fünf |
| H6 | six | sechs |
| H7 | seven | sieben |
| H8 | eigth | acht |
| H9 | nine | neun |
| H10 | ten | zehn |
| H11 | eleven | elf |
| H12 | twelve | zwölf |
Note: The LED to GPIO mapping can be easily changed in source code
See detail description on https://github.com/fablab-wue/piClock/blob/master/prepare.md
In short:
- Setup network/WiFi
- Disable SPI, 1-Wire, Serial
- Install Python3, pigpio-lib
- Download source from GitHub
- Autostart at boot the ~/piClock/franconian.py
Linux experts will configure the RPi in no-time. Less experienced users (like me) needed more time for configuring than for wood-working and soldering.