I have just finished my binary wrist watch project (well, the new revision anyway). I was surprised at how small I was able to make it compared to last time.
I chose to go with the “super-yellow” color LEDs as they fit the purple OSHpark PCB very nicely. The biggest challenge was actually making a good looking wrist band for the watch. I originally intended to use a design like this but it turned out that due to lack of enough para cord I had left, I went with a simpler design that I had done once before.
Unfortunately I used the wrong footprint for the PIC when laying out the PCB. The PIC comes in a SSOP-20 package and the footprint marked “SSOP-20″ in the KiCAD library is actually a TSSOP-20. Ridiculously enough there’s also a separate TSSOP-20 footprint in KiCAD.
I was able to get away with bending the pins of the SSOP inward and then reflow soldering it to the TSSOP footprint. It’s a bit of butchery but I couldn’t give this one to Mr. Murphy.
After getting all the hardware wrapped up, I could start coding. The watch can be woken up from sleep mode (display off, only RTC running) by holding the right button for one second. It can be put back into sleep mode by holding the right button for one second again.
For more detail: Binary wrist watch guarantees being identified as a nerd