After all, VFDs also have a heater, grids, anodes and are encased in glass. And they glow in tha dark.

VFDs are common on VCRs. I have a few of them I took from some broken VCRs. Last night I was working on how I could use them as vacuum triodes. I don’t have much experience with real vacuum tubes so I had to invent some, possibly wrong, arrangements, but I finally got something.

I’m not going deep into the structure of VFDs as I wouldn’t add anything to what is available on Wikipedia or on manufacturer’s websites. Just need to know that the heater (or filament) is made of thin straight metallic wires that emit electrons (thermionic effect) when heated by current. The electrons are accelerated by the electric field generated by a voltage applied between the heater and the metallic anodes, the metallic plates shaped as digits and pictograms and that are covered with fluorescent paint which glow when hit by the electrons.

A number of thin grids are placed between the cathode and groups of anodes with the purpose of screening or letting go the electric field generated by the voltage at the anodes.
A negative voltage between one of the grids and the cathode will generate an electric field opposite in sign with the anode-cathode one, reducing or voiding at all the latter. The electrons will be stopped and will not reach the anodes behind the grid and those digits will be dark. A positive voltage at the grids is actually necessary to pre-accelerate the electrons.

That said, I reached this final layout.

The grids are connected together as well as the anodes. I connected a headphone between the anodes and the positive of the anode voltage through a decoupling capacitor.
The grids are polarized by a 100k Ohm resistor to the positive and the audio fequency is fed into the grid through another decoupling capacitor.

The heater generally requires 2-3 Vdc. When powered from AC they give a more uniform brightness but in our case DC is better, to limit hum into the headphones.
The anode voltage may vary between 20 to 40 Vdc, depending on the model. The connections to the filament are the only ones to be really careful about as misplacing them and feeding with the anode voltage wil blow the heater. Looking closely through the glass of the display the filament and their connections to the connection pins can be easily found.

The power into the headphones is limited but I never expected more than this.
A novelty, nothing more, possibly.

Might behave better as low power preamplifying stage for a real vacuum tube power final stage.

That’s it, and I had fun.

Addendum (after comment from Hiro Protagonist) : The arrangements of the anodes in the drawing is simplified as the display I used has multiplexed digits, that is the segments and pictograms are paralleled inside the display to minimize connections to the driving IC is usual applications. This limits the use of the VFD as a multiple triode.

Here is how I installed Processing on my Linux Acer Aspire One. It took a little bit of time and I learned something also in the process. BTW, I can’t imagine a less convenient name (processing) to look for in the Internet : ANYTHING related to computers has to do with processing ! LOL

The steps :

I Downloaded processing-0148.tgz from processing.org. The file will go to the ‘Downloads’ directory.
Then I unpacked Processing-0148.tgz to the directory Processing-0148 inside the ‘Downloads’ directory.

Went to Java Sun website and downloaded Java SDK for Linux (jdk-6u10-linux-i586.bin).
Followed the install instruction from Sun specifically for the self-extracting bin :

cd /usr/share
sudo su
./home/user/Downloads/jdk-6u10-linux-i586.bin
That is : changed directory to where I wanted to JDKto be installed into, became root and executed the bin to install the JDK. Answered yes when required to agree to the terms of license.
A few moments more and JDK was installed.

Than moved Processing directory to /usr/share :
mv /home/user/Downloads/processing-0148 /usr/share/

Now the trick suggested by Fry and Reas necessary to make processing use the JDK and not the IcedTea Java which won’t work for processing and that is supplied with the Aspire One :

cd /usr/share/processing-0148
mv java java.bak
ln -s /usr/share/jdk1.6.0_10 java

The latter two steps backup the original java directory of processing and create a crosslink to the installed JDK.

To execute processing:

cd /usr/share/processing-0148/

./processing

That’s it.

I had hard time finding it in a local computer shop. When I found it the clerk said “the Windows one ….. finished” But I wanted the Linux one “mhhhh….the white one is sold out !”, he said then. What the … this is not a Mac, “I want it blue !” I said.

At last he gave up and handed me the small treasure box.

Not a cheap computer, 300 Euro – no way to find it for less -  this could be a great present instead of a super sleek mobile phone.

This one worked out of the box immediately, the WLAN connected immediately to my access point, just set the encryption mode and key. My HP printer connected immediately : I just followed the instructions from a good forum and could print the test page in 10 minutes overall .

Made a few more hacks like getting rid of the Acer desktop and took out the XFCE desktop and made some others hack.

I had hard time getting my Bluetooth at work but I was sure linker3000 would make it and today, Oct 4, he posted an update with drivers and instructions ! I love this Linux community. Now I have my GPS receiver Holux GPSlim240 send its messages to the console !

Next step : have Processing run, as for now I’m getting the following

java: xcb_xlib.c:50: xcb_xlib_unlock: Assertion `c->xlib.lock' failed.

./processing: line 17: 23577 Aborted   java processing.app.Base