06 August 2017

A cute VFD display

At the Marzagla rally I spotted a small box with a 7-segment symbol and "Nixie", all hand drawn/written. Inside there were three small 9-digit VFD's looking NOS. Five € for the three.

The display looked like the Russian IV-18 and IV-21, with all pins on one side, but they have no external markings and one extra digit. So they are not an IV-21. To simplify things these tubes had an insulator slipped over filament wires: that left [9 + (7+1) =] 17 more wires to idenfity (9 digits, 7 segments, 1 decimal point).

Back side. No markings!
The visual area is about 3.5 cm, and the whole tube is about 6.5 cm long. I can make a desktop clock/display since you won't be able to read at a distance.0

Since the filament was already identified, I began from it. I started at about 1Vdc and raised it in partial darkness in order to observe if the filament would start to glow (not good, sign of too much current). I settled at 1.5V and started looking for segments and digits. A good news is that it glows even at 12 V, so I will have not to worry of having and dealing with a higher voltage as most VFDs require (30 V, some even more).


Spreading the wires.
Luckily grid pins are on one side and segments on the other. Not willing to design a PCB for this display I took advantage of the long leads and build a simple adapter on veroboard. I will chop off the extra board under the display and let it hang out of some sort of vertical structure .... when I will be done with all the electronics involved.

A not-so-quick and dirty adapter.