Stylish Neon Watch Tells Time with Neon Tubes and Is Programmed via a Light Sensor

Nixie tube watches have a unique aesthetic. These watches have a couple of tubes that warmly glow with numbers. Inspired by these watches, Lucas Volwater designed a wristwatch with no numbers. Instead, the Neon Watch uses four neon tubes to create a display that mimics an analog watch face with a twist.

The secret to making the watch face work is that each neon lamp has two electrodes. By activating them independently or together, four lamps create 12 positions. For example, the lamp at the 12 o'clock position uses both electrodes to indicate the "12" position. For the "1" position, only the right right electrode of the same lamp illuminates. This method means the watch can only display a single digit at a time. So the watch shows hours and then minutes as two "digits."

Volwater designed the watch with a Microchip ATmega48A microcontroller (MCU). While this 8-bit MCU does not have a real-time clock, you can use one of its counters as a "real-time counter" with a dedicated 32.768 kHz crystal as a timekeeper. The downside to this approach is that if the (only) battery dies, the wearer must reset the time. Fortunately, the 110 mAh battery lasts just over four days.

The neon lamps normally stay off to conserve the battery. However, there are no buttons to activate the lamps, nor are there any to set the time! Instead, an OSRAM SFH320 phototransistor serves both functions. First, the MCU illuminates the display for 16 seconds when the sensor detects a simple hand wave. And the other use is programming the time.

In 1994, Timex introduced the Datalink. It was the first watch that downloaded data from computers "wirelessly." An optical sensor detected flashing patterns from a CRT (or an optional adapter with an LED.) Similarly, Neon Watch uses the SFH320 phototransistor to transfer data. An application on the PC makes a flashing pattern that the Neon Watch decodes as the current time!

The components all fit on a single round PCB with a 40-millimeter diameter. Inside the case, there are only 9 millimeters of height available. The transparent cover takes up 2 millimeters, and the neon lamps have a 4 millimeter diameter. Volwater realized that those components, plus a battery, didn't fit within the constraints. So, the PCB is only 0.8 millimeters thick instead of the typical 1.6 millimeters, allowing everything to fit.

Another tall component is also critical for operating the boost converter for the Neon lamps. It is a miniature transformer. While these are not manufactured today, at one point, they were plentiful. Their original application was part of the charge circuit used in camera flashes.

For additional pictures, check out Volwater's Neon Watch blog post. There are also videos of it demonstrating the time display and transferring data.