The Tempus Fugit word clock displays the time using the ’12 hour’ format in words spelt out on an 8 by 8 letter matrix, time is displayed in 5 minute slots [5,10,15,20 …]. The correct time is maintained when the unit is not powered by an on-board battery backed RTC chip.
With an 8 x 8 matrix there obviously have to be some compromises, for instance ‘HALF’ and ‘TWO’;
Even with the limits of an 8×8 matrix you can display time to a + / – 3 minute accuracy.
Three rear mounted pushes allow the time to set and adjusted as needed. Instructions will also be included on how to optionally set the TF time via a connected PC.
In normal operation the TF does not need to be connected to the internet or a host computer.
Operating and build Instructions for Kit TF can downloaded from my TF Wordclock GitHub Insturctions supplied as a download.
The finished printed circuit board size will be about 112mm x 70mm, it could have been little shorter but with these dimensions the length to width ratio works out to 1.6 which is often referred to a ‘Golden Triangle’ – considered by many artists and architects to be the most aesthetically pleasing form of a rectangle, so I decided to stick with it.
With the exception of the display and Pi Zero / Arduino most other components are mounted on the rear of the board, – Pi / Arduino could have gone on the back but why hide a thing of beauty !
- Display – 60x60mm red
- No surface mount parts on the TF board, so should not be challenging to solder with a basic level of competence
- Raspberry Pi interface, compatible with old and new Pi’s as it only uses the first 26 GPIO header lines
- Power for the board is via Pi’s micro USB connector or for the Arduino it’s Mini-B USB connector [note connecting leads and PSU are not supplied with any of the options]
- The real time clock (RTC) is battery backed with CR1220 coil cell, [because of postage restrictions the battery is not included]
- There are 3 monetary switches, these are used to allow the clock to be set and to shut the Pi down cleanly when not connected to a host computer
- Sockets for the Arduino, Pi Zero and display will be included in all options. Sockets for the integrated circuits will also be included for the kit version
- The circuit includes a light dependent resistor (LDR), to allow the display brightness to automatically dim in low light conditions. It is also possible to manually override this.
The Letter Matrix
Built and Kit options include a simple acrylic English letter overlays. Other font options can be easily created from the down loadable templates. Non proportional font like Courier work the best
- Python code is available for down load via GitHub for Raspberry Pi setup and as a sketch for the Arduino
- The Python codes assumes you are Python 2.7x
- The Nano code has been developed using Rev 1.6.7 of the Arduino IDE
The Nano clones use a CH340 USB to Serial chip, I have found they work ‘out of the box’ with window 8.1 /10 and with a Pi3 running the latest Raspbian [as of April 2016]. You may need to install additional drivers with Macs and earlier versions of Windows.
What is not included
- Until the availability of the The Pi Zero’s improves I am not able to include it with any of the options – it is obviously not required if you are going down the Arduino route
- The SD card for the PiZero, but as an extra option a 16G Micro SD card pre-loaded with current Raspian and the Python code for TF is available
- A PSU adapter, I generally run the prototype with the official Pi PSU, but any PSU rated to work with a Raspberry Pi should be fine. For the Arduino option you will need an Adapter with a Mini-B USB connector or you can connect directly to the Nano PSU supply pin – check theArduino website for details
- Case or mounting for the TF
- Tools and solder to build the kit options