The ChronodeVFD is a personal project I’ve been working on for a couple of months. It’s a wristwatch built around the IVL2-7/5 VFD display tube. I originally purchased a few of these tubes to build a standard desk clock, but after playing around with them, I realized I could probably build a wristwatch too. The tube has a number of features which make it more suited than most Soviet-surplus VFDs for this purpose.
nominal 60mA filament current @ 2.4V, but still works with ~35mA @ 1.2V.
It’s small — only 1.25 x 2.25″
It’s flat, as opposed to the round tubes like the IV-18, which would be much clunkier in a watch design.
can operate from a relatively low grid voltage of 12-13V (up to 24V)
pulls only about 2.5mA/segment from the grid rail @ 12.5V. (“8″ = 20mA)
One other feature that I like about this device is that unlike nearly every other VFD tube, the IVL2-7/5 has no opaque or diffuse backing behind the digits. It’s completely transparent front to back, which means that if you put it on top of a circuit board, you can (with a bit of backlighting) see the PCB below.
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