VFD IV-11 tube filament PSU

11 years 7 months ago #1021 by terrym
Hello folks
after seeing some of the posts here I'm amazed and somewhat trepidatious to even post this question, however the expertise is certainly in this realm. My question is that I want a simple filament supply, hopefully sourced from the +5V supply used to power my logic chips.

In the past I've used some brute force approaches:
-current limiting resistors (about 80-100mA, at 1V, but the display brightness never seems bright enough)

-a bunch of 1N400X diodes in series to bring the voltage from 5V down to 1.5V or so, at whatever current the tube seems to want. This actually produced a satisfactory brightness according to my tastes.

Perhaps these approaches are sufficient for my needs, just wondering what others have done.

Important note, this is only supplying a single digit clock, so one tube only.

Also important, electronics knowledge from old text books and internet research, but strictly hobbyist and always seeking enlightenment.

VFD is new to me after the Numitrons, and I don't have the "courage" to do Nixies justice at this time!

Thank you

ps. I owe my inspiration to building numitron and vfd clocks to the the gentleman who runs this site:


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11 years 7 months ago - 11 years 7 months ago #1028 by Mr.Nixie
Replied by Mr.Nixie on topic Re: VFD IV-11 tube filament PSU
Hi Terrym,

for a single digit VFD clock it's the most economical way to use a linear regulator to get the filament voltage. A switching power supply is a little critical due to the high current and the low supply voltage of 5V.
Please also note, that the IV-11/12 needs a negative gate voltage of at least -0.5V to complete turn all segments off.
The filament voltage should be in the range of 1.5 to 1.6V @ 120mA. I would prefer a circuity I've attached as schematic - do not use the LM317 "L" type due to the higher current than 100mA.

Last edit: 11 years 7 months ago by Mr.Nixie.

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11 years 7 months ago #1029 by terrym
Thankyou Mr. Nixie. I didn't think the LM317 would have enough headroom from a +5V line, but it isn't my usual linear regulator (I do use the 7805's for the logic side of things, with the MC34063 just to generate the +27V or so for the Anode side.
Interesting that you raised the filament voltage via the diode to make the Anode GND as the effective negative voltage you mentioned. Clever, I'm so glad I posted (and gladder that you responded). I will build that circuit soon and hopefully have positive results to gloat about. Thanks again


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