Round Nixie Watch - Part Eight

The Nixie Watch was a huge success. I managed to build and sell about two hundred watches by the summer of 2009. At that time, I tried to buy more parts to build a batch of watches, and found that the ADXL311 tilt sensor was obsolete and unavailable. Calamity! 

I decided that it was time to redesign the circuit board to use a more modern part. The ADXL335 is a 3-axis tilt sensor that's packged in a more modern plastic QFN package, compared to the thick ceramic package of the ADXL311. Since it has three axes, I could mount it to the rear board instead of on its own little riser board. This simplifies the watch assembly procedure. 

I also changed to a surface-mount crystal and a more rugged, washable variable capacitor to prevent production problems. A few other tiny details in the board layout changed as well. The CPU chip was changed to a 16LF722 from the now-obsolete 16LF872. 

The watch case is still unchanged. 

After selling another hundred watches in 2010, I decided to change the PC board yet again to make it a bit easier to manufacture. The tilt sensor was moved to behind the lower right corner of the right tube, and the left side of the round PC board was squared off. This style is currently being produced and sold.