Fiat lux

We have a North-facing kitchen that, despite bay windows and lots of electric lighting, always felt uncomfortably dark. It was crying out for a skylight.

The 4′ square skylight totally transformed the kitchen during the daytime. Areas that used to be “the bright spot near the window” are now “the dark spot away from the skylight”.

I also wanted to add more illumination at night, so I put in a hidden area for lights recessed behind a lip around the opening. I love the diffuse, natural look of the skylight during the day, and figured that with upward beaming lights shining on white paint and the translucent material in the skylight itself, I could get a facsimile of daylight at night.

Getting the geometry right was an interesting exercise. Due to the roof’s slope, a square on the roof projects downward to a rectangle on the ceiling. We ended up with a square in the ceiling and a square in the roof, and connecting them with a bend like a waveguide.

The 45 degree flare has a lip made of ripped wooden handrail. I wanted maximum reflectivity, and wasn’t keen on having the possibility of ignition of the wood, dust or paint if there were hotspots from the lighting, so I fashioned some inside channels out of 4 inch aluminum flashing.

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I was hoping to use incandescent light rope, since I admire the color shift when it dims. But I found that a conventional light rope is not nearly bright enough for anything other than a dim night light.

So I bought an LED rope light. Here it is in the channel:

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The effect felt strange. It’s a very diffuse light, very unlike a candle or incandescent bulb; not even like moonlight, which leaves a shadow. Maybe moonlight in fog. Combined with the relative dimness, it is very dreamlike. It was interesting but not quite right for the kitchen, where detailed work is done with knives.

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LED strips are expensive so I ordered a more powerful one from China, which was a disaster in all sorts of ways, even after I rewired it to the correct voltage.

The vinyl actually started to turn brown when I left it running at the factory’s claimed power level. I consider myself fairly safety conscious, and this thing was completely out of the question. Vinyl is not an appropriate material for dissipating power. Lesson learned.

After fighting with dimmer compatibility issues, I ordered these LED tubes in the T8 fluorescent bulb form factor. The specs showed decent power (22w each) and color temperature.

The outside of the tubes are half aluminum and half translucent plastic. They were very sturdy and have a bright, even light. Despite the fluorescent form factor, they only require power at one end without a ballast, so I broke out the lamp wire, flux and heat-shrink.

The result was very satisfactory; when pegged at full power the skylight is now the brightest thing in the room. Unlike with a rope light, the flare corners aren’t lit, but the consistency along the bulb is excellent.

These bulbs are designed to cooperate with dimmers. They fade on and off in about a second, presumably due to internal capacitors. I haven’t heard any of the characteristic whine of an internal switching power supply. I anticipated the aluminum being a heat sink but it never felt hot to me at load. I was still happy to have a metal channel for it to live in, just in case it develops hot spots.

The only thing I’m not yet entirely happy with is the color temperature. The kitchen is a mixture of fluorescent, incandescent and halogen sources that live together acceptably well. In comparison the skylight is too obviously the highest color temperature (that is, a “cold” light with more blue light).

I bought some color correction gels (heat-safe filters meant for a theater lighting) and eyeballed their effect relative to the other lights in the room. Here you can see the untreated, 50% CTO and 100% CTO-filtered light:

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To my eye these worked nicely to bring the color temperature down without looking colored, so I’ve order some 25% CTO sheets to treat all four bulbs.

Et facta est lux.

One response to “Fiat lux

  1. Margaret Anderson

    So exciting to see the progress you have made. The lighting is wonderful!

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