The project is an eye-catching and unique Word Clock which literally tells the time while being powered by an Arduino Duemilanove which acts as the controller. The clock uses ULN2003A driver ICs instead of discrete transistors used to drive the array of LEDs. A set of Darlington transistors in a convenient DIP package is contained in the ULN2003A. The finished product can be seen in the photo below.
The schematic diagram of the controller board is also shown below and the Arduino controller can be simply plugged into the new PCB. The controller board is made using toner transfer and drilling of holes.
The mounting of components will start after etching, sizing, drilling, and cleaning the PCB. The parts are populated in order of size which starts by mounting the 6 jumpers since it is a single-sided board. The image below shows the board populated by parts.
High intensity LEDs were used in this project which have about 10 degrees of beam width. This signifies that getting an even illumination will require about 30mm from the LEDs. The fiberglass material display board is also shown below with LEDs mounted into a series of pre-drilled holes. The LEDs are soldered on the back of the board to a piece of 26-way ribbon cable that is terminated with a 26-way IDC socket.
A couple of push buttons for time changing need to be mounted onto a piece of board material by wiring some short lengths of wire to the buttons to connect to the terminal block on the controller board. The photos below show how the buttons were connected where a red and a black button was used.
To program the controller, the Arduino editor is needed. This is done by connecting the controller using a USB cable and pressing the “Upload” button after opening the project sw. file in the editor. The sketch will be transferred and should start immediately and the LEDs that are not connected will remain dark. The testing of the display is shown in the image below. A debug function in the software that prints the time out every time that it is updated via the Arduino serial port as well as flashing the Digital 13 pin every second is also included.
Since the LEDs are powered by the external power connection, it is necessary to note that the LEDs will not be seen lighting up when the controller is being powered by the USB cable. The device is connected to a DC power supply when testing the unit. Every word should light up in sequence when the unit is plugged in with the clock starting to run. The orientation of the LEDs and their wiring are checked if one of the words fails to light up.
The final stage of the project is to make the word stencil for the front of the clock using a piece of PCB material for etching. The stencil was created in the mirror image with the copper layer on the outside. Some more PCB stock to use as 30mm baffles were cut prior to using the display. The photo of the stencil is shown below.
A simple enclosure was made using chipboard which was trimmed to a uniform width for the top, bottom, and sides. Some back supports were mounted into the box after cutting a piece of thin ply as the back. The controller PCB was then mounted while carefully using washers between the back of the board and the wood. Some photos of the construction of the enclosure are shown below.