Questions about VFD

[nebula]

I would love to know how these work:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140303558420

(Model FG165S1) - these look like the display in the Roland JX-8P.  I know they are old-school, but I really like the look of them.

But all those pins ... judging from the way the traces look on the back, the segments would be lit with a common anode or cathode for each character, along with a separate lead for each segment.  Then you've got a couple of extra pins on each end that appear to energize the entire display, requiring a high voltage (presumably this is the "grid"?) 

Can anybody offer a quick primer on the electrical properties of VFD?

[stryd_one]

VFD ? tiny neon tubes.

[lucem]

Current heats up heating wires, grid controls on-off states.

Heating is required for electrons to traverse from cathode to anode.

That thing is a tube, simply said - and VFDs can actually be used as amplifiers ;)

[SLP]

Warning - while you were typing a new reply has been posted. You may wish to review your post.

Aaaahhh!!! ( ;))

VFD ? tiny neon tubes.

not really...

VFD ? Electron Tube

There's a common cathode at the back of the Display. It's heated up, so electrons are set free (Thermionic emission, like in any other electron tube).

Those electrons are accelerated by an electric field (like in a CRT or in any other electron tube). They are flying towards the anode. Between the cathode and the anode there is some kind of mesh. If this mesh has a negative potential, the electrons won't go through it. If the mesh is neutral or positive, the electrons will make their way through and fly towards the anode (-> Triode) , which is covered by some chemical substance (ZnS, IIRC) which lights up if it gets hit by electrons (-> CRT). And that's basically it.

In neon tubes there's a electric discharge through some gas. This gas emmits UV-light, which in turn makes the substance on the inner side of the glass tube light in a visible color.

edit: http://en.wikipedia.org/wiki/Vacuum_fluorescent_display  ;)

[nebula]

I think I'm getting this.  The Wikipedia page is helpful, but it links to this page:

http://hem.passagen.se/communication/vfd.html

... provides some good guidelines for the DIYer to fire up a scavenged VFD.  It suggests that there are three different methods for filament drive in VFDs:

• AC Drive ("most popular method for the audio system and large-size VFDs.")
  
• DC Drive ("mainly used for small-size VFDs driven by the car batteries.")
  
• Pulse Drive ("used for relatively small size VFDs which are driven by the car battery not by DC drive.")
  

Which drive method is most likely to be required by the displays in the eBay link I posted, above??  It looks like DC drive would be the easiest to implement, but if you're using an AC supply I guess you could tap off that before it gets rectified.

I might buy one of these flats of displays to experiment with.  25 pieces for 37+15 bucks works out to $2.08 USD per display, shipped to me.  If anybody wants 5-20 pieces, let me know, and maybe we can share.  I'm on the fence about this.

[stryd_one]

not really...

Of course not - That's not an 'equals' sign ;)

[ultra]

Of course not - That's not an 'equals' sign ;)

thank god.  i only had three beers after work...