STOP PRESS:I posted some of these photos on the MAKE Flickr pool and they blogged it!
As a kid I had a soft spot for an old valve radio that lived in the kitchen for many, many years. A little like this:
Something about the valves ("tubes" in the US) appealed to the Science Fiction fan in me I think. With their complex variety of rods, meshes, coils, heaters and shields they reminded me of miniature futuristic cities under glass domes.
On a whim one day I bought three large tubes on eBay ($3.99!).
I wasn't sure what I'd do with them, but when they arrived I arranged them in a pleasing little group on my book-case. This inspired me to mount them on a small wooden plinth. I don't know why, I just like the way they look. Mysterious.
I thought, "wouldn't it be cool if they glowed!" This set me off on a much more complicated project. I bought three more tubes on eBay, but much smaller and without the bakelite bases ($2.25!).
Then I did a little research into driving LEDs with a 9V battery: put them in series with an appropriate resistor.
I bought some LEDs, resistors and a small breadboarding base online from RadioShack.
When they arrived I did some experiments and found that it basically worked, I could illuminate one of the tubes from beneath.
The LEDs weren't particularly bright, around 20 mcd (20 millicandela, a 60W bulb is about 120 candela) so I visited a local RadioShack
and picked up some brigher ones (600 mcd), a small toggle switch and a project box.
I also got a 9V power supply, so I could plug my project in and forget about batteries.
I visited a local surplus electronics store and got a 1k ohm potentiometer and knob.
Then I got out my (cheap, crappy) "smoldering iron" and put it together.
Breadboard:
