The Ice Tube Clock, available as a kit, uses a lovely IV-18 vacuum-fluorescent display (VFD) tube.
Unlike Nixie tubes, which are current-operated gas-discharge displays, VFDs are thermionic voltage-controlled devices, just like the vacuum tubes used in old radios and amplifiers (as well as some modern high-voltage equipment). Specifically, VFDs are a special kind of directly-headed triode.
VFDs have three basic parts: the filament (cathode), the grid, and the phosphorescent anode(s). In the case of the IV-18 device used in the Ice Tube, the entire tube has two filament wires stretching the length of the tube (wired in parallel). Each separate digit has it’s own grid, and each of the 7 segments of the number display are ganged together is an anode. By quickly multiplexing the grids you can make the device appear to display all the digits at once.
In this photo you can see all three electrodes. Those two dark lines running horizontally across the photo are the filament wires.
Here you can see a couple of illuminated digits. The nebulous nature of the illumination across each segment is caused by variations in the electric field, and the grids casting an electron shadow onto the segments.
Make a robot friend with Adafruit’s CRICKIT – A Creative Robotics & Interactive Construction Kit. It’s an add-on to our popular Circuit Playground Express, FEATHER and other platforms to make and program robots with CircuitPython, MakeCode, and Arduino. Start controlling motors, servos, solenoids. You also get signal pins, capacitive touch sensors, a NeoPixel driver and amplified speaker output. It complements & extends your boards so you can still use all the goodies on the microcontroller, now you have a robotics playground as well.
Get the only spam-free daily newsletter about wearables, running a "maker business", electronic tips and more! Subscribe at AdafruitDaily.com !
I was wondering if it is possible to buy just the tube (and the breakout board), as my ice tube clock fell two weeks ago and the tube shattered inside the acrylic box. I could order the IV-18 VFD retro display from ebay, but I’d rather continue supporting you guys.