I used six TPIC6B595 high power shift registers (one for each digit) to drive the displays.
I had originally planned to use four digits in my clock. Fortunately one of the displays I ordered arrived with the decimal point broken off. After emailing SparkFun a photo of the damaged display, they sent me a replacement and allowed me to keep the original damaged display as well. So I then had five digits. I thought a six digit display would be more useful than a five digit display so I purchased one more display from SparkFun.
I had been trying to figure out what I'd do to make the colons needed for separating the hours, minutes and seconds. I thought I might use a red LED to make the needed dots. The broken decimal point gave the idea of trying to use it above one of the attached decimal point to make a colon. It took a bt of work to solder wires to the broken decimal point, but I was able to get the decimal point to light up when power was connected to the display.
I carefully removed the decimal point from one other digit. I used this second decimal point to make another colon.
I plan to display output from my lab equipment with this display. None of my equipment use more than four digits after the decimal so by placing the decimal point deprived digits at the beginning and end of the display, I could still use decimal points when using the clock to display data.
I included a DS1307 RTC with the project so the time is preserved when I turn the display off.
I'm working on some code to use a Wii Nunchuck as an interface for setting the time and for starting and stopping countdowns. I plan to add a wireless interface. I'd also like to make it easier for the clock to be portable. I'll need a way of attaching the battery and Propeller controller board to the back of the clock.
The six digits are attached to corrugated plastic (it looks like plastic cardboard). I used nylon nuts and bolts to secure the digits. I made the frame from expanded PVC. I learned about expanded PVC from Gordon here on the forum. It (expanded PVC) is cool stuff, just as Gordon claimed. It cuts easily with a table saw.
I ordered a piece of transparent red acrylic from Tap's Plastic (I actually ordered two pieces, since two piece didn't cost much more than one piece). The frame and front are all held together with Gorilla Tape.
I noticed in my controlling program, I have the duty cycle of the LEDs set to 50%, so the display should be able to be brighter than shown in the video.
Sometime in the future, I might paint the PCB of all the digits the same color. There are three different colors of PCB in the display. I personally think this is rather annoying since the PCB will likely be seen when theses are used in their intended purpose. For now, it doesn't bother me enough to paint them.