Reinventing
the wheel (4)

Original page created on 29/07/2022; updated on 13/11/2024.

Architectural LED lamp

Requiem for a fluorescent lamp

I’ve had this desk lamp, which has three 14 W fluorescent tubes, for about 15 years. The original ballasts didn’t last very long. I had changed them for soft-starters which extended the tubes’ life, which were also changed in the end.

Now, it’s out of order, two tubes burnt out, one ballast too. The reflector is yellowed and cracked, as is the body. It’s time to change it. However, I want to keep the articulated support, still very functional and quite big (50 cm per arm). I also keep the switch.

Remarks

• Before starting the following, I looked for a replacement LED lamp of about the same size (at least 60 cm long) and with a sufficiently large articulated support, in vain;
• LEDs currently have a colour rendering index (CRI) still far from that of some fluorescent tubes (90).

So, here is an inexpensive batten with quality LEDs (Samsung). Its dimensions are 600 × 75 × 25 mm. Specifications: 20 W, 2400 lm, colour temperature 6500 K, 3-year warranty, but CRI > 80 only… I’m not under any illusions: better than 80 means close to 80…

The Ledvion batten

This batten is really light! The one-piece body is made of a plastic material that is both white on the underside and translucent on the top. It comprises 2 rows of 60 LEDs wired in groups of 3 in parallel, the groups themselves being in series, on a very thin printed circuit glued to a thin sheet aluminium heat sink. The whole assembly is slid into grooves in the body, flush with the base, so it cannot be fixed through the base.

That’s why I want to find another way to fix the strip… on what, by the way?

A wooden stand

On second thought, a wooden board thick enough to accommodate the electrical connections might do the trick. So, I cut a 620 × 100 mm board, 20 mm thick, from an old pine shelf. The wood should give a nice look to the future lamp.

The machining is done: the place for the support, drilled with a Forster drill, the place for the switch, milled with my Proxxon milling machine, the space for the connections, hollowed out with the router. After connecting the cable, I fix the strip with thick double-sided tape, but it doesn’t hold: after a few hours, it comes off. I suppose this is because the board is warped.

So, I decide to replace my salvaged board with a solid finger-jointed beech board. In fact, I order two pieces in case I fail the first one. Anyway, the price of the wood is quite low compared to the shipping costs…

Order received, I’m a bit disappointed by the differences in colour of the finger-jointed pieces, but it seems that this is normal for this quality of wood. And the other qualities are not available.

Here is the machined board being varnished. You can see the colour differences, which are a bit too pronounced for my taste.

Although the new board is perfectly flat, the double-sided adhesive bonding still doesn’t hold.

Photos of the finished lamp

The electrical connections are made with plug-in connectors.

Click on the photo for a closer view of the connections.

Top view.

Bottom view.

Lamp on.