The VFD display is on!

It’s been a month since the last update. Check out the previous post for the complete history of this project! Being a hobbyist sometimes mean you don’t have as much time to sink in your projects as you would like to, but you have to live with it.

Nonetheless, there has been tremendous progress on my big VFD display made out of Soviet-era IV-25 tubes.



The 3D prints and assembly

Prusa finally decided it was time to ship my i3 MK3 5 months after ordering it (never again by the way; you’ve lost a customer for life Prusa!) and so I could finally assemble the brackets on the PCB that are holding the tubes.

VFD panels printed and assembled.
VFD panels printed and assembled.


All six digits side by side
All six digits side by side


I painted them matte black but didn’t bother further processing them as they will not be seen in the final product. I have to say they turned out really well and it sure makes for an impressive size!

The VFD panels from the back


The rest of the electronics

I will create a proper motherboard for the project but for now everything is wired to some protoboard that is just enough to make the display work. There’s a lot of power management involved because this project requires quite a few power rails:

  • Standard 12V in from which everything else is derived
  • 20V for the VFD filament
  • 5V for the SN75518 VFD driver chips and the H-Bridge VFD filament drive circuitry
  • 3.3V for the ESP32

The ESP32 drives the display through a SN74LVC8T245 3.3V to 5V logic converter. I successfully clocked the 18(!) daisy chained SN75518 chips at their theoretical speed limit of 1Mhz, but sometimes I noticed a few glitches. The wire mess probably doesn’t help and the display currently works well at 600Khz. I will re-test 1Mhz once I have a proper PCB.

Before I finalize the motherboard, I’d like to code as much software as possible in the esp32; and add speakers. Stay tuned for the next update!




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