Blue LED Light Box in an Altoids(-like) Tin

I have Seasonal Affective Disorder.  For years, I treated it by sitting in front of a very bright light every morning.  Some people use daylight or full-spectrum bulbs for their light therapy.  But over the last few years, blue lights, particularly LEDs, have become a popular alternative.  I've discovered that, for me at least, they are the most effective kind of SAD treatment.

But blue-light light boxes are expensive.  So I decided to try making a low-cost alternative version with flexible LED strips.  It turns out to be very easy to build one into a mint tin.  (I can't get Altoids where I live, but there's a locally available knockoff whose tins are the same size.)

I've used mine for several months now, and I'm having much less trouble with my SAD than I did with my bright-white light box.  Also, I kind of like the tiny, tidy package of it.

This project requires you to be able to solder.

Step 1: Materials and Tools

MATERIALS

1. Mint tin. I can't get Altoids tins where I live, but these are precisely the same size and construction. I used a blue one, for obvious reasons.
2. 45 cm of self-adhesive blue flexible LED tape, plus connector and adapter. You need the stuff that's made to be cut into 5-cm lengths and soldered together. I can get 50cm and a connector for €4 and an adapter for €9 (plus shipping and handling). I don't know prices outside of my area.
3. Cardboard: you'll need at least twice the footpring of the mint tin, about 2mm (1/16") thick.
4. 3 plastic bottle caps to use as spacers inside the box. (If you don't have the right size, you can layer up cardboard instead.)
5. Wire to connect the LED circuit. I used jumper wires for breadboarding, which are really, really easy to work with. With more patience, you could use ordinary wire.
6. Wire to tie the cord down. Its electrical conductivity isn't important. Its ability to hold stuff together when twisted is.
7. About 3" of ribbon to make the tab to pull the LED panel up for maintenance purposes

Edited to add:

8. Stiff card (like unlined index card) for the diffuser.

TOOLS

1. Triangle/ruler
2. Scissors
3. Pencil
4. Awl, for piercing the tin
5. Pliers to cut wire and crimp
6. Needle-nosed pliers. Actually used because their closed jaws are a good cone to widen a hole in the tin.
7. Soldering iron, solder and soldering iron holder

Not shown: glues (ribbon to cardboard, bottle caps to cardboard)

Step 2: Create Cardboard Inserts

Cut two pieces of cardboard small enough that you can get them inside the inner lip of the tin. One of them is going to be the base, holding the cord and spacers in place inside the box. The other will be the light panel.

Step 3: Place the LEDs

Let's talk about the LED ribbon. It's marked out with cutting lines every 5 centimeters. Each 5-cm section has three LEDs and a resistor, as well as paired connection points at each end. If you don't cut the ribbon, each section's + terminal stays connected to the + terminal of the next strip down, and the - to the -. If you cut it, you're going to have to make the connections yourself.

Some LED ribbon marks the + and - on both sides of the cut line. Unfortunately, some doesn't, which means that you have to keep track of it yourself after you cut. (+ and - matter for LEDs…connect them the wrong way and they won't light up.) But I noticed that when the LED labels on my tape were the right way up, + was at the top of the tape, and - at the bottom. So I used print orientation to keep track.

The easiest way to build this project is to have the strips alternate orientations on the cardboard, so that + and + are together, and - and - are as well.

Mark the center-line of the cardboard and lay the first strip of LEDs along it (since you have an odd number of strips). Add the other strips, using the positions of the lights and resistors to make sure that you alternate orientations.

Step 4: Clip Cardboard

Where a + terminal is next to the + terminal it wants to connect to (or a - next to the next -), it's easy to connect them: a glob of solder, and you're there. But you can't just connect all of the terminals to their near neighbors, or you won't have a circuit on your board. Some terminals have to be connected to more distant partners. See the photo of the LED board with the red and white lines for the connections required to power the whole board.

To keep things simple, we'll run the more distant connections through wires along the back of the cardboard.

First, mark where you'll be connecting adjacent terminals and where you'll have to connect distant ones. Make sure that you have a continuous path from beginning to end for both + and -.

Then notch the cardboard next to those separated terminals. (I made two parallel cuts in the cardboard and pulled the intervening tab out with needle-nosed pliers. You may find a better technique than this.). Be careful to leave a tab of cardboard between nearby cuts to separate the wires and prevent short circuits.

While you're at it, make similar notches for the wires that will go to the connector.

Step 5: Place Wires

The next step is to bend the wire you'll use to connect more distant terminals. I used jumper wire for breadboarding, because the straight portions of it are long enough to make hooks that will crimp onto the cardboard. The jumpers I had were too wide, so I bent them in the middle to bring the ends closer together.

If you don't have jumper wires, try to use relatively stiff wire bent into the right shape. Each piece should be at least 2.5 cm/1" long. First bend it into a squared-off U shape as wide as the distance between two terminals (mine were 6 mm / 1/2" apart) Make a C-shape in each end, just large enough to hook around the cardboard and land on the terminal of the LED strip.

You'll need 8 wires. Hook each one onto its pair of terminals and pinch them shut so they stay in place.

Step 6: Solder

Then it's time to solder all of those connectors. I'm not going to try to teach you to solder (you really don't want to learn from me!). There's a good guide to doing it here.

Once you have all the connections soldered, you can test your board by plugging in your connector and touching the wires to the end of the circuit. You'll quickly see if any connections need to be re-soldered.

Step 7: Cut and Solder Connector Cord; Attach Ribbon

Once you have the board wired and soldered, it's time to fit the connector cord. My LED supplier sends 30cm (12") cords, which is way longer than I want inside my tin. I cut it a little short of 12cm (call it 4 1/2"). The length you choose depends on where you want the plug to come out of the box. Fit it carefully, then cut, strip the outer casing from the two wires for an appropriate length, and strip the insulation from the ends of them. Coat the wire ends in solder.

Bend the wire ends in the same C-shapes you'd bent the LED connectors into, and crimp them in place. Solder them. Plug the whole thing in and check your connections.

Using PVA (white glue) or similar, glue the ribbon down to the back of the cardboard so that a tab of it will stick up when the LED panel is in the box. This will allow you to take it out if you need to.

Step 8: Pierce Box

Once you know where you want your cord to come out, mark it on the outside of the box. Be sure that the cord comes out low enough that the box can close, but high enough that even when the hole is full-sized, it's a cardboard thickness from the bottom.

Find the center point of the future hole. Pierce it, from the outside in with the awl. (That way, the ragged edges of tin will be on the inside.) Then use the needle-nosed pliers or similar to force the hole larger (again, outside in). Turn it as you go so that you get a round hole, and stop when you can just force the end of the power cord through the hole from the outside in.

The inside of the hole will be a mess. Use pliers to pinch the torn edges of metal flat. Try to pad them so that they don't mark the outside of the tin too much.

Step 9: Place Spacers and Fasten Cord Down

Now it's time to use the second cardboard cut-out you made in step 1. It'll make the base panel of the light box.

You'll need spacers to keep the LED panel at an even height from the bottom of the box.You want to use ones that are as thick as, or just thicker than, the thickest part of the connector. The caps of my 1.5-liter cola bottles are just right: 12mm (7/16") tall. If yours are much taller, it's difficult to fit the LED panel and diffuser inside the upper lip of the box. In that case, glue layers of cardboard together to make a filler of the correct height.

Glue the spacers down on the base in such a way that the LED panel will be stable.

On the base panel, mark the path of the connector wire from the hole in the box to where it rises to meet the LED panel. Mark the end of the head of the connector. Pierce a couple of holes in the base panel on either side of that point and wire it firmly down, so that plugging the cord into the connector won't push it into the box.

Wire the cord down to the base panel in at least one more place.

Step 10: Assemble

Put the base panel back into the box. Put the LED panel in place above it. Plug it in to test that you haven't broken any solder connections. If you have, fix them.

Step 11: Add Diffuser

Now it's time to fit the diffuser. It serves two purposes: it scatters the blue light, and it protects the solder joints.

It shouldn't fall out of the box on its own, so cut it a little large and expect to bend it to make it fit in place. Cut it just wider than the width of the tin (about 5.8 cm / 2 7/16"). It should cover all 9 LED strips, but will need to leave some of the cardboard of the LED panel exposed or you won't be able to get it in. For my LED strips, that was about 7.75 cm, or just over 3 inches.

Bend it slightly to pop it into place, and voila! You have your own mint tin light box. Happy winter!