Glen Akins' PoE VFD Tube Clock Tells Time Accurately
This custom clock uses Ethernet for both power and data, displaying the time on six bluish-green glowing tubes.
First spotted on Twitter, Glen Akins has been building a six-VFD tube display. These components resemble Nixie tubes, but produce a nice warm bluish-green glow that can be seen on some stereos and vintage automobiles. The other interesting element here is that he’s using PoE (Power over Ethernet) to set the time, as well as provide power.
When activated, the clock gets its IP address and DNS via DHCP, and negotiates a 7.5 watts power level to keep the tubes glowing. It then gets the time from an NTP server and displays it on a half-dozen VFD tubes via three Microchip HV5812 high-voltage display drivers. To keep things extremely accurate, once an hour it rechecks the NTP server and corrects for any drift.
Akins notes that this project, like many, was completed in stages, first working on the PoE/power supply components, then placing components onto the tube board itself. Notably, the build involves a variety of power levels, including a 1.5 volt supply to take care of the tube grids, a 5 volt supply for the display drivers, 3.3 volts for the SPI interface, and 25 volts for the tubes themselves.
It’s seen running with a Particle Photon and a bench power supply in the first video below. In the second, it’s powered over Ethernet, with the onboard PIC18F67J60 having received the proper IP address. From there is was a matter of completing the software to get and display time on the six-digit display.