Working with VFDs

vfd

We love old display technology, like Nixie tubes, but they’re often difficult to work with because they require higher voltages than digital logic. Vacuum florescent displays (VFD) fall into this category. While not necessarily “old”, they are becoming far less common than LCDs. The main benefit of a VFD is that it actually produces light directly; it doesn’t require a backlight. You’ll find these displays on various players and appliances: CD, DVD, VCR, microwaves, stoves, car headunits, and others.

[Sprite_tm] had written off some VFDs, but recently revisited them with renewed interest. He started by testing what sort of voltage would be required to drive the display. It took 3V for the filament plus 15V to drive the grids. There are VFD controller chips available, but he wanted to get this working with what he had on hand. He had experience with older 40xx series logic, which can be powered by much higher voltages than 5V 74xx. His final schematic has three 4094 serial to parallel chips with an ATtiny2313 controller. A 5V power supply is dropped to 3V with diodes to drive the filament while a boost converter brings it up to 15V for the 4094s that switch the segments. While the code is specific to this display, it would be a great place to start your own project.

Comments

  1. Really cool stuff, I love VFDs.. totally underrated display tech in my opinion…

  2. Josh says:

    I have a few displays laying around. I might just dig out some old ones I got a few years ago when Nixies were all the rage. My only problem is what to use it to display. anyone have ideas?

  3. Richard says:

    it’s worth remembering that vfds can do more than merely display information – as they’re thermionic devices it’s possible to do so much more if you enjoy fiddling for it’s own sake. :-)

    http://www.hpfriedrichs.com/rr-vfd.htm shows you how to use them as amplifier tubes, for instance – and pretty much anything that can amplify can also oscillate if you want it to – and occasionally when you don’t!

    a nice new-year challenge would be to build a radio using vfds as the only active components – the internal construction of some will allow you to find two or more triodes in a single package once you figure the pinouts, so an am-only receiver for your local station with sufficient output for a small speaker or some walkman headphones shouldn’t be very difficult. ;-)

  4. strider_mt2k says:

    richard that sounds like good reading to me.

    I wouldn’t know where to begin, but I’m more than ready to live vicariously through others when it comes to esoteric projects like that.

    this itself is a very cool project!
    major stuff from spritesmods

  5. waggy says:

    @richard

    Tom Kipgen is inspiration for unusual and gorgeous tube and crystal radio design, and he has two posted, each using one EM83 magic eye tube, the Green Tree and Winking Wedge sets.

    http://www.kipgen.com/radios/sale/tubesets.htm

    Apparently, they are both based on the first schematic by Jara “Krysatec” (“Rat”) on the following page.

    http://www.schmarder.com/radios/visitors/jararat.htm

    If anything I make ever looks half as good as Tom’s stuff, I’ll consider my life complete.

  6. Allegro makes some very convenient VFD driver chips: http://www.allegromicro.com/en/Products/Categories/ICs/vfdisplaydriver.asp . I used the A6812 in a project.

    The filament should be powered by AC. I used a 555 in 50% duty cycle configuration driving an H-bridge. If DC is used, there will be a brightness gradient because the filament is the cathode and its voltage differs from left to right.

  7. russ_hensel says:

    A nice thing about these displays is they come for free in manu microwave ovens and vcr or disk players. These devices also have other nice parts.

  8. faustian says:

    MC1488/SN75188 also do great as drivers as long as you do not need more than 30V and have symmetric power supplies available….

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