Story and supplies

This all started when I took apart an old scanner that I found. I think it was a higher end model (Fujitsu fi-6230), I'm still impressed of how nice it's been designed.

Inside I found 3 separate scanning units and they all use florescent tubes as light sources. I usually don't bother reverse engineering those, but in this case, each of them had it's own standalone driver circuit on a nice little standalone board that just takes in 24V DC and takes care of the rest. I'm pretty sure that not reusing them would count as a capital sin in every religion.

The whole scanning unit can be found for around 35 USD (search for "Fi-6230 Scanning Module"). The inverter lamp driver boards alone are around 10 USD for 2 (search something like "1 Set High Voltage Board 6225 CX-025624D024 Fits For Fujitsu Fi-6230") and I successfully used them to power fluorescent tubes from screen backlights too.

Lamp Driver Boards	Lamp
CX-025624D024

The lamps look pretty fragile and the manual says they contain some mercury too, so caution would be a good idea.

Wiring

The scanner also came with a 24V DC power supply, but I wanted to have some dimming ability so I added a step down DC-DC voltage regulator to the mix. After replacing its trimmer pot with a proper potentiometer (I went with the fader style), I wired everything up for a test.

Very simple circuit, really: 24V DC goes into the step down converter, whatever comes out of this goes into the lamp driver board and that's it. The fader has the same ohm value as the old trimmer pot so it's wired directly in its place.

The Dimming

Now we get to the juicy part: how it behaves when starved. At first, going down from full 24V, the intensity starts decreasing to a point where the magic start to happen. The column of light starts to shrink towards one end ("the thicker wire one" would be the scientific term) until it goes completely extinct. It's the closest thing to real magic that I ever experienced. I was also clueless enough for this to come as a surprise, so it really blew me away (and not in the "warning: high voltage" that's written on the driver board kind of way).

The Build

I started on the idea to use a tall vase as an enclosure, mainly to protect the aforementioned fragile lamp, but all the reasonably sized and reasonably priced vases that I found distorted quite badly. I now know a glass bell (like the ones found at Ikea) would've been what I needed, but now I like it without.

Anyway, I always start by sketching the existing objects in CAD so that further I can build around. This way I have a starting point AND it will all nicely fit in the end without having to adjust my design. I also sketched bounding boxes for the electronic boards and subtracted those from the base body.

Based on the diameter of the vase I sketched the base for the desk lamp, I carved space for electronics from the bottom, built a screwable cover (wood screws work well in 3D printed plastic even after a dozen unscrews).

After adding countless meaningless details, the base got the over-engineered badge of approval so I could finally move on to build the supports for the tube. I built it in 2 pieces so that they'd hug the top end of the tube to gently but firmly hold it in place, while one of them also hides the wire.

I was planning to use a thin copper band for extra looks, so I added a small indentation for that and later super glued the band in place.

3D printed everything in PLA and assembled.

Add the fader knob and a metal greeble (the inner burr from a coffee grinder) to break the plastic aesthetics a bit.

Check out the youtube video to see the final result in action and some more details along the way (including a CAD sketch fast forward walk through).