If you have trouble with low mood in the winter, or even outright depression, you may benefit from light therapy. You can buy medical appliance light boxes, but they're expensive, and may not be as good as something you can put together yourself using light fixtures from a home improvement store.

Winter blues seems to be caused mainly by the shorter day length and over all less exposure to bright light. Perhaps this was adaptive in northern Europe, when there was nothing much to do during the winter but hunker down and save energy, hoping you'd have enough food to make it through to the spring, but it's a drag in the modern world, where we're expected to function year-round.

There is evidence of special blue-sensitive light receptors in the eye which sense light for regulating the Circadian Rhythm, which is presumably also involved in Seasonal Affective Disorder. Because of this blue sensitivity, light used for therapy needs to have a large amount of blue light. The most common light source is a Fluorescent Lamp.

Since the light is sensed by your eyes, it doesn't work unless your eyes are open. It's commonly recommended to glance at the light itself every couple of minutes, while sitting at the light and doing something like reading, with an exposure period of 30 minutes or more. I've found that what works best for me is to get up before dawn and “expose myself” then. (Light therapy joke. You can wear clothes.) This way, I'm increasing the day length. There's some online resources at http://www.cet.org/, including a test you can take to find the best time for light therapy based on your natural Circadian Rhythm.

Because of the blue response of the day-length receptors, you need a "full spectrum" type lamp, which has blue-emitting phosphors. These are often sold under names such as “daylight natural”. Other clues are the “color temperature”, which is a number such as 4100K, where higher numbers are bluer. Full-spectrum lamps are also rated for color rendering (CRI). Any lamp rated for CRI will probably do, but you want the ones with higher color temperature, cooler or bluer light.

There are also different sizes and shapes of lamps. I've mostly used the T8 x 48“ 32 watt lamps in recent light boxes, because they are good value. The main disadvantage of these bulbs are that they are 4' long and relatively fragile. You do not want “cool white” bulbs. These are not full spectrum. The pictures below show the first light box I made, which uses the older T12 (1 1/2” diameter) 40 watt bulbs, which no longer work well, due to reduced mercury content regulations.

I've also made a box using the F32-T8 6“ U-Bend bulbs, which I found in full spectrum. A fixture with two bulbs gives you the same light as two 48” straight tubes, but in a square form that is more suited to table-top use.

The thing that holds the lamps and makes them light up is the “fixture”. When you go to the store, first see what kinds of full spectrum lamps they have and how expensive they are, then look for a fixture that will hold them.

Aside from being sturdily constructed so that they can be moved around without falling apart, the main difference between a medical light box and an ordinary fluorescent fixture is that has a filter to block the fairly low levels of Ultraviolet light that the tubes emit. I don't feel that the UV filter is entirely necessary, though at one point it did seem I was getting a bit of sunburn when I had my face only a couple of feet away for a long time. A light box also needs a power cord, and a switch is a nice convenience.

The simplest way to get started is to get a “deluxe shop light” fixture. This has a cord with a plug, a switch, and a metal reflector. On the downside, there is no diffuser, so you are looking directly at the bulbs, which may be uncomfortable, and increases whatever UV risk there might be.

This is the first light box I made, which uses the old-style T12 tubes, and has no switch.

This view shows the tubes, and also shows one of two handles mounted on the sides. The handles are useful with this type of fixture, because the diffuser wraps around the fixture, but isn't itself sturdy enough to grab onto for moving the light box around. These are home-made handles, but I've also used drawer-pull type handles. Use the holes in handle to mark the position, then drill holes to mount the handle. Attach with small bolts and nuts (like a #8 machine screw.)

I've also put aluminum foil behind the tubes. This is optional, but makes it somewhat brighter (a “ specular reflector”).

This picture (also at top) shows my latest version, mounted on the wall in my kitchen, and uses 12 32 watt tubes (384 watts) in three four-tube fixtures. These are all mounted on a piece of plywood, together with the switch. This makes attachment to the wall easier, and makes it possible to move as a unit. When you fire this baby up, you can't even tell if the other kitchen lights are on or not. Maybe partly because it's on the wall, it seems more like a window into an alternate sunny reality than like a light.

Wiring is basically the same as for a single fixture, but you connect the fixtures in parallel. The switch is an ordinary switch like you'd mount on the wall, in this case in a “handy box”. This photo shows a detail of the switch and wire routing:

The wiring required is pretty simple, but may be daunting if you've never done any electrical wiring work before. For a cord, it's usually cheapest to buy a short three-wire extension cord and then cut the female (socket end) off, though you might also find a replacement cord with a bare end.

This view shows the cable clamp mounted in the end of the light. This mechanically holds the cord so that when you tug on the cord it doesn't cause internal disruption in the wiring. This is an electrical hardware item, a “romex” or “NM” cable clamp. I suggest wrapping the cord in electrical tape where it is clamped to prevent the cable from being damaged, since the clamp isn't designed to hold this type of cable. The clamp is mounted in a “knock out”, which is a circular indented area that has been precut in the fixture housing, with the remaining bit of metal held on by just a small tab. You can pry out this disk of metal with a screwdriver. Bend it back and forth until the metal fatigues and breaks. In this particular fixture, the plastic end trim covers the knock-out and needs to be cut too. There will also be a knock-out in the middle of the back of the fixture.

You should put on a three-wire (grounded) cord. Not only does this reduce shock risk, it may also be necessary to get the fluorescent lamps to light reliably, especially as they age. Don't be intimidated by the mess of wires you see in this view. You only need to make three connections: live (black), neutral (white) and green (ground). This view shows that in my first light box, I actually didn't connect the ground (green wire), which gives me a chance to show how to do it.

First strip the wire by running a sharp knife in a ring around the insulation, cutting through about an inch from the end. Or use a wire stripper, if you have one. The pull off the end piece of insulation, exposing the bare wire. Twist the wire ends with your fingers so that the individual copper strands are twisted together in a bundle.

Then wrap the wire clockwise around the grounding screw and tighten with a screwdriver:

The black and white connections are made using “wire nuts” (blue). You'll likely need to buy small size wire nuts suitable for connecting two 16 or 18 gauge wires, though the fixture may come with wire nuts that will work. Stripping the wire ends for the black and white wires is the same as the ground wire. Then twist together the two wires (clockwise), preferably using pliers. After twisting, trim the length of bare wire to a bit less than the length of the wire nut, then twist on the wire nut with your fingers. It should get tight enough that you can't turn it any more with your fingers. If bare wire is exposed at the bottom of the wire nut, then twist the wire nut back off and cut the wire ends a bit shorter. It's also a good idea to put a couple of wraps of electrical tape around the wire nut and wires to prevent a short circuit, especially if you're new to using wire nuts.

If you want to add a switch, then you need to select a switch, drill a hole in the fixture to mount it, and connect it in-between the black wire from the cord and the black wire for the fixture (or “in series”, as we say.)