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Thread: 12 x 40 VFD (help!)

  1. #1
    Constant Bitrate
    Join Date
    Jul 1999
    Location
    Decorah, IA, USA
    Posts
    196

    12 x 40 VFD (help!)

    Awhile ago I posted about a 12 x 40 Vacuum Fluorescent display I found on eBay. It arrived today, and I'm wondering if any of you electronics experts can help me get it hooked up. I already posted a long message to a different board, so I'll past that below. You can see some pictures of it <a href="http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=176482862">here</a>.

    ---

    The first thing that caught me was that the display is huge. At least 25% bigger than I expected. And heavy. The weight is due mostly to the fact that the display is behind a piece of .25 inch-thick glass. Surrounding the glassed-in area is a 3/8-inch thick piece of hard rubber, which would lead me to believe this was used in an industrial environment. There are no chips on the board at all. The complete unit is .75 inches thick, 11.25" wide, and 7.75" tall. The display area, from the upper-left corner of the first character in the first row to the lower-right corner of the 40th character in the 12th row, is about 6 x 3.25.

    The board has 12 sets (one for each row) of 18 pins, each labeled 1ROW, 2ROW, 3ROW, all the way up to 12ROW. Then there are two sets of 20 pins each that are labeled "G1~G20" and "G21~G40." Could these be grounds? There are also eight pins, two pairs on the left and two pairs on the right of the board. Each set of pins is labeled with numbers for each pin. For example, the 5ROW set is labeled with a 1 at the first pin and a 36 at the last, 6ROW goes from 37 to 72, and they go counter-clockwise around the board up to 480.

    At the bottom of the display, there's an empty glass bulb about the size and shape of a Christmas tree light, which seems to be a closed tube that goes into the space under the glass. My only guess would be that the space under the glass is a vacuum, and the bulb breaks under pressure instead of the glass plate breaking and damaging the display. Either that or it breaks in case the interior heats up too much.

    One interesting thing about the display is that there are what appear to be 24 very thin wires strung about 1mm above the surface of the display. There are 24 of these wires in all, two for each row of characters. They each seem to be connected to one of the board's pins, although I can't tell which, the numbers add up.

    Also, if you hold the display up to the light, you can see all the way through the translucent board. You can also make out a serial number stamped onto the board. It reads "Itron DC40125A Japan", which is slightly different than the "DC40125A2" Itron label glued to the back of the board. Another number is visible when you hold the board up to the light -- "P-61902PCB" -- which appears to be the serial number of the board itself.

    So far, this is all I know about the display, which doesn't really help me hook it up (if I tried to stumble my way through it, I'd need a lot more displays to break before I figured it out). I e-mailed the Itron folks about two weeks ago, and at first they claimed that:

    The part number you referred to in your e-mail, DC40125A2, is very similar to Noritake part numbers, but unfortunately Noritake does not or has not made a 12 row by 40 character display. ... Noritake does
    manufacture displays with 40 characters per row, but only up to 8 rows.
    My guess is that it was a custom display ordered by someone, not something they mass-produce, but the way I received it was in the original Styrofoam packaging with a big Itron logo on it. I hope to hear back from one of their people soon, as they've always been pretty helpful, but I'm guessing I'll have to spend my dime on a phone call.

    But anyway, do any of you have any idea how I would hook this thing up? Any help would be appreciated. It's a really neat display, and I really want to be able to do something with it. So any ideas?



  2. #2
    Constant Bitrate
    Join Date
    Oct 1999
    Location
    CA, USA
    Posts
    118
    No interface board at all? I think you just bought a door stop!

    Your display is fluorescent, like a fluorescent light bulb. It doesn't run off 5V but more like 60V. Those thin wires across each row is the cathode filament. This heats up and gives off electrons that get attracted to your pixels which light up from their phosphor coating.

    You'll need fluorescent driver chips for your multiplexed display, a high voltage inverter, and an interface chip to drive the drivers based on a serial or parallel input.

    Unless you want to spend hundreds of dollars buying all the pieces, 100's of man hours labor figuring out how to put it together, you'd be better off finding a display that already has all the drivers and logic needed.
    Digikey I believe sells some fluorescent displays complete and ready to go that interface like LCD displays.

  3. #3
    Constant Bitrate
    Join Date
    Jul 1999
    Location
    Decorah, IA, USA
    Posts
    196
    Well, so much for encouragement. But seriously, I know who manufactured it, and I know more than enough about the product for them to at least give me all the datasheets for it. The Noritake folks (who make Itron displays) have always been quite helpful, and for a price, I'm quite confident that I can get everything I need to get this to work. I posted this message here, because Noritake's enginners aren't exactly speedy, and I was hoping to get a head start. And really, is $12.50 (what I payed for it, including shipping) too much considering what I've already learned about these things? I don't think I've wasted my money. If I had paid $400 for it, then yes, I'd be an idiot, but if there's a chance I can get this to work for less than the cost of the VFD that I would have bought if I hadn't bought this one, then I think my money was well-spent. Even if it doesn't end up as a part of an MP3 player. Hell, it'd make a great display for a terminal. So, anyone else have any helpful advice?

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