I used E-wire to make up the glowing cathode element. I am sure that different colours, patterns, or alpha numeric characters could be used in the display.
I managed to fool my father, from a couple of feet, that it was a real vacuum tube. He had worked with tubes when he was a young man, and at first sight was shocked by the size of it.
The final tube is about 13 inches or 32cm (see D cell battery in picture for scale)
1 Glass dome (I think this came from a clock, and was Thrift store find at one dollar)
2 ABS Plumbing pipe coupler (four dollars at a hardware store)
3 Luminescent wire, EL wire , ( I bought this at Ikea for a few dollars)
4 Scraped computer hard drive and mounting rails (Free!)
5 Scrapped computer parts ( I used the screws, drive rails, stand offs and other scrapped bits, all free)
6 Black Arborite, or black painted, wood half an inch or 1.5 cm thick (Ikea for three dollars)
7 Large nails ( I used nine, six inch nails and cut the pointed ends off)
Things to consider:
Make sure you have your glass dome with you when you buy your pipe or pipe coupling.
You want a snug fit. I had to sand out the inside of the pipe to get the glass to just fit.
I wanted to be able to remove the dome, but you could glue it if you need to.
Trace out and cut a circle of black wood to fit inside the tube, you need one to fit inside and rest on the ledge that the pipe coupling has. This is where you will mount the tube elements.
The glass dome will rest on this circle of wood.
I mounted a hard drive platter on the center of this and all the various scrap bits of metal I had to make the inside of the tube and tested the dome fit each time I added an element.
Be creative, use Google to find tube images for reference. I used what scrap I had lying around.
Make the base for the nails (fake connectors) You could leave these off, or make a bigger socket to plug it into.
Trace an inside outline of your ABS pipe on your wood and cut out what will be the bottom and sand or file to get a nice snug fit.
Cut the pointed tips off your nails, and make them all the same length ( I used nine)
Drill well spaced holes in the wood, just big enough to admit the nails, and hot glue the nail heads to the wood on what will be the inside of the tube.
Once you have the wood inside the tube use some small screws on the edge to hold the tube to the wood base.
I used EL wire for the "Emitter" element for my tube.
This pictured EL wire unit from Ikea cost about $2.00 and can produce a constant light or flash on and off. The Ikea name for this was "Glansa" , but I am not sure if they still sell it. The Ikea unit runs on two AA batteries, and an external wall wart could be used to power it.
EL wire can be found all over the internet and goes by Luminescent wire, or EL wire try http://www.elwirecheap.com/
I just hung the EL wire over some rods taken from a scrap cd drive, but I am sure that you could make characters, logos, etc. and maybe make a large fake nixie tube, as there is easily enough space inside the tube for a micro-controller.
I drilled some holes to thread the wire into the space between the top and base.