• It should be possible to swap out the PIC16F877 that Doug used for a PIC16F887, which has the same pinouts, with minimal changes to the code, should you decide to rebuild his clock without any modifications aside from upgrading the microcontroller.  And added benefit of using the 887 versus the 877 is that the 887 has a built-in oscillator with a default frequency of 4MHz, so an external oscillator is no longer needed.

Inconsistencies

• The parts list supplied by Doug lists the power regulator as a 78L05, whereas the outline on the PCB layout is for an LM7805.

I had a few other things in mind, but I originally drafted this post a while ago, and now no longer remember what else I was going to write.

Nice, but not €889 nice.

Someone named Doug from Australia (?) came up with an Instructable detailing how to build your own Word Clock for significantly less money, though it may take some refining to make it pretty.

I don't know Doug or Megan.

This guy Doug also redesigned the faceplate for the clock to include both his name and I’m assuming the name of his significant other, Megan.  Since I already plan to change the circuit, I’ll probably change this too, since I don’t have any good friends named Doug or Megan, and certainly not a Doug or Megan who I’m both friends with and are significant to one another.

Proposed Modifications:

It seems that the new version have four extra LEDs, one at each corner, to provide more accurate time.  The original clock could be accurate to within five minutes, displaying something like, “It is five past one”.  The new clock should keep track of exactly which minute in that five minute interval it actually is, e.g. 0 = x:x0 or x:x5, 1 = x:x1 or x:x6, 2 = x:x2 or x:x7, etc.  This should be relatively easy to implement — the easiest would be to use one of the pinouts from the PIC microcontroller to send a digital signal to either a series of transistors that would essentially count to five and reset.  Since I don’t have a whole lot of experience designing that kind of a circuit, the fastest way for me would probably to use a shift register to virtually expand the number of pinouts and address each LED for the minute counting individually.

You can't turn it off.

David suggested that an extra button be added in order to disable illumination of the clock by the LEDs, in case you know, you wanted to actually go to sleep in the same room as that clock.  This would maybe need a pusbutton connected to a comparator that would be connected to an input pin on the micrcontroller, then using one of the pinouts from the microcontroller connected to a transistor to turn on and off the power connection for the LEDs.

In addition, the original clock has 110 characters in an 18″x18″ square frame with a fairly large border around the text area.  I’m guessing each letter in the text area has a square inch to itself, for a text area dimension of 11″x10″ (WxH).  A problem I see with the clock made according to the Instructable is that there are a few more letters, 117 total, in what seems to be either the same or a smaller area (likely smaller), which results in some light leakage between and around characters being backlit.  Therefore, sufficient spacing between characters for dividers to segregate the various words from one another will be necessary.  One possible root of the problem for the Instructables clock is spare PCB panels were used as baffles, and if these spare pieces were etched to remove the copper first, then they would be translucent, leading to light leakage.

Cost Issues

The single largest component cost for this project would probably be the circuit board — turns out they’re really expensive, either to have printed or even if you’re going to use a generic board and do all the wiring yourself.  Looking just at the circuit board needed to mount the LEDs for the display, the costs are pretty high, and this doesn’t even include the etched circuit board used as a face for the clock, or the controller board.  For example, this 10.5″x10.5″ circuit board would be perfect as a surface to mount the LEDs and necessary transistors and resistors, but it’s $62, or $1.78/sq. in.

It is also possible to etch your own board, and at least for the display portion of the clock, this would require something 10″ square or larger.  Digi-Key has 12″ square unpunched, copper-clad boards starting at $19 single-sided, 1 oz. copper, or $21.50 for double-sided.  The price goes up significantly for pre-punched boards that are copper-clad.

Thinking about this more, it should be possible to shrink the face of the clock, as long as the size of the letters were shrunk as well, which would also reduce the cost quote a bit.

In any case, the third circuit board option would be to design it with some CAD software and have it professionally printed, like from any of these places: barebonespcb.com, expresspcb.com, or batchpcb.com to name a few.

Why use screw terminals?

It seems the best option would be to divide the project between hand-wired parts on a board and a professionally-printed board.  The controller board should be professionally printed, and the LED backing for the clock should be wired by hand, with ribbon cable used to connect the two halves via the screw terminals, or better yet, a pair of sockets.  The face of the clock could be etched as before, though I’m sure there’s a better way.