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The process of making a salvaged VFD Arduino-friendly.

You can get your hands on some very interesting components when disassembling old electronics. One such I’ve found was this VFD (Vacuum Fluorescent Display). Trying to reverse-engineer the controller was, however not the way to go as all ICs on the board were covered with glob-tops. So I decided to de-solder it from the control board and build a simple driver. Here’s how to do it with a MAX7219 (I’ve had a few left from a previous LED project) and some other components.

The filament pins (the two left-most pins) require around 3V to operate. Grids and anodes(digits and segments) both need around 18V to provide sufficient contrast.

The MAX7219 cannot be used to drive a VFD directly as the logic is a bit different from 7-segment common-cathode LED displays. Instead of pulling the currently multiplexed digit to ground, it needs to be supplied with 18V as well as its corresponding segments. The NPN transistor with a few resistors did the trick.

Finally, UDN2981s are used to supply the segments and digits with 18V. Its inputs are triggered by the outputs of MAX7219

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