Touch-sensitive LED Lantern

Twenty five years ago, my grandfather made me a flashlight by soldering a light bulb to the bendy terminals of a flat, 4.5V battery. As a device, it was crude and simple, yet it didn't just light up my pillow fort that evening. It fueled my desire to learn, to explore, to understand, and to create. I hope that my first instructable sparks that very same maker spark that's been keeping my hands itching since then.

Now let's talk lanterns.

Pictured above, the lantern that I made was inspired by traditional Japanese architecture – where a wall or a door is constructed out of paper lined over a wooden frame (look up the term "shoji" if you're curious). The same concept has been applied here, only on a smaller scale. Light is emitted from a string of LEDs on the inside, while a touch-sensitive circuit acts as an on-off switch.

Before we proceed to step 1, I need to state a very important DISCLAIMER. This instructable involves the use of tools that might cause serious injury, discomfort, and/or damage if not used properly. Please use common sense and take care of yourself if you choose to recreate this project or any of the steps described within.

Note that all units in this instructable are metric!

To make the top and bottom pieces of my lantern I used tilia wood since it is cheap and abundant where I live, but you may use any kind of wood that looks good and that you feel comfortable working with. High-quality plywood may also be OK to use. Don't bother using MDF, particle board, or OSB for a project of this kind. Now here's what the process looked like:

1. CUTTING: Using a jigsaw, I cut two pieces of tilia wood measuring 13 by 13 by 2 centimeters. If you don't have the right tools or skills for the job, hardware stores that sell timber can usually cut the pieces for you as well.
2. SANDING: Then I clamped the two pieces together using several clamps and sanded their sides until they were perfectly even in size. I started with rough (60 grit) sandpaper that removes a lot of material quickly. Then I moved on to 120 grit and finally 240 grit until the sides were nice and smooth to the touch. Ideally, you shouldn't be seeing any traces from the sanding.
3. ROUNDING: Don't remove those clamps yet! It is also a good idea to round the corners of the pieces. Again, start with a rough piece of sandpaper, then move on to something finer to make the curve nice and smooth.
4. CHOOSING: Finally, visually inspect and choose the better-looking piece, as well as its better-looking side. Sand that side as smoothly as you can. Make sure that piece and that side go on top of your lantern. You can mark it lightly with a pencil if you need to then rub it out before applying finish.

Four thin and long pieces of wood hold the top and bottom piece of the lantern together. They are all 19 cm tall and 1 by 1 cm wide. I cut them out from a single, 1-meter-long piece of timber that I got from a local hobby store. You may find me referring to them as "the outer frame" in the next steps of this instructable.

A hacksaw is all you need to cut the four pieces easily. Use a pencil to draw a mark where the cut has to be made. It is a good idea to wrap the spot in masking tape and then cut over it to prevent the wood from chipping.

Don't worry if the pieces don't turn out perfectly even. It is okay for one or two to be a millimeter longer or shorter than the rest. You'll see why in the next step.

There are dozens of ways you can join two pieces of wood. The mortise and tenon joint is one of the easiest and most common techniques, so I decided to take the same approach for my lantern. Basically, I carved mortises (a mortise is a fancy word for a rectangular hole, in my case) in the top and bottom pieces and stuck the four frame pieces in there. Here's how I did that.

1. Using a scrap piece of wood 1 centimeter thick – a leftover from the outer frame – I marked a line 1 centimeter away from every edge of my bottom piece. I made the marks on the upper side of the bottom piece. You should end up with a rectangle with sides of about 11 centimeters.
2. Using the same scrap piece, I outlined the mortises in every corner of the rectangle that I drew. Every mortise was going to be 1 by 1 centimeter wide, which are the exact width dimensions of the outer frame pieces.
3. Using a chisel, I carved out the mortises. Don't worry if you've never used a chisel before. This was my first time, and the results were great. I used a 5-millimeter flat chisel from a dirt-cheap wood-carving set that I got from the hobby store. First I pressed the blade along the outlines to mark the hole. Then I gently began removing layers of wood following the direction of the wood grain. If feeling unsure about all this, practice on a scrap piece of wood first! My holes ended up being 8 millimeters deep. I made sure their sides and bottoms were nice, clean, and flat. The frame pieces should fit tightly, without wobbling much. Make sure you remove the masking tape from the previous step before trying out how they fit!
4. Finally, I sanded the side with 240-grit sandpaper. This gave it a nice, smooth feel and removed all traces of the pencil markings.

Before applying any glue, I made sure that all four frame pieces fit well in the holes. Then I applied a liberal amount of glue and inserted the pieces into the holes with moderate force. I used the right angle of my ruler to make sure that all pieces were perpendicular to the base. Wipe any glue squeezing out with a damp piece of cloth or paper towel, but not toilet paper.

At this point I realized that I had forgotten to drill a hole for the cable of the 12V power supply. But it was still doable. Using my Dremel tool and a 3.2 mm bit, I drilled a hole in the side of the base 22 mm deep. Then I drilled another hole at an angle from the top while aiming for the end of the first hole. I nailed it perfectly. With a little wiggling, I was able to push the power cable through the hole to make sure that it fits well. Then I removed the power cable – it is too early for it to be there.

While the glue was drying I carved the mortises in the top piece of my lantern. There's nothing to add here really. After sharpening my chisel, I simply followed the same process I described in step 3.

My lantern was starting to take shape. It was time for a dry run. Using some fine-tuning (read: careful bending of the outer frame pieces) I managed to fit everything together without glue. This meant could go ahead and apply glue to the top piece mortises to stick everything together permanently. As you can see from the photo, I used a couple of clamps this time around for a tighter fit and to ensure that the top and bottom were perfectly perpendicular to one another.

Once the glue was dry, I applied two coats of spray lacquer over what was slowly becoming a lantern. Spray lacquer is super easy to work with, so if you're a beginner, that's the finish to pick. Make sure you follow the instructions on the spray can and apply the finish in a well-ventilated area. Other finishes like shellac, varnish, or danish oil would also work, but working with them is a bit more messy.

Note that the inner area of the bottom piece I covered with masking tape so that no lacquer would stick there. This is where the lighting element would stick to, so it is better to leave that area untreated.

While the lacquer was drying, I assembled the electronics required for this project to work. A generic 12V power brick is what I used as power supply since my LEDs required 12V to light up. The power brick was rated for 1 amp, which was plenty for my needs.

To find out how many amps your power supply should be rated for, use a multimeter to find out how much current three of your LEDs consume (LEDs from LED strips are grouped in threes, hence you can cut out no more than three to measure their consumption). If three LEDs consume 30 milliamps and you want to use 30 LEDs, you'll need a power supply that can deliver at least 300 milliamps at 12V. I'd go for at least 500 mAmps in such a case – to be on the safe side and since there will be other circuitry involved.

UPDATE: Apparently, you can get LED strips where the LEDs aren't grouped in threes.

The LEDs are connected to the power supply through an n-channel MOSFET (IRF 520, in my case, or anything that can handle a few amps). The latter acts as a switch – when a signal is sent to it, it lets current through and turns the lights on.

The signal is sent by a PCF8883 chip, which is an IC designed for touch button/switch operation. This chip comes in SOIC8 package, so it won't fit on a perfboard. You'll need to use one of these – a SOIC8 board adapter. You solder the chip to the adapter and then the adapter to the perfboard. One of the pictures above shows the chip soldered to the adapter – tiny, isn't it?

Since the chip requires 3 to 9 volts to work, I also used an LM7805 voltage regulator.

All electronics were populated on a single 2cm by 8cm perfboard from a kit like this one. The green wire you see hanging is what's going to be connected to a sensing plate.

UPDATE: To increase the sensitivity of the touch sensor, either increase the area of the touch plate or replace the 470nF capacitor with a larger one up to 2500nF.

I hope you like olives. Instead of a light bulb, I used a strip of LEDs wrapped around a tall and narrow glass jar. Originally I was going to use a PVC pipe, but the deadline for the First-time Author Contest was quickly approaching :)

When picking the LED strip, I intentionally went for "warm white" LEDs because they are a bit more yellowish. Most of the so-called white LEDs are annoyingly blue and are definitely not suitable for the bedroom.

When wrapping the LED strip around the jar or pipe, make sure you start at a slight angle. You want the LEDs to be as tightly wound as possible, but you don't want them to overlap. You can do a practice run first, without exposing the adhesive at the back, then cut the strip to size. Note that LED strips have markings where cuts should be made.

I soldered wires to the strip and twisted them together for stability. For extra strength, I used 2-component glue to glue the wire to the jar – at a point close to where they were soldered to the LED strip.

Using 2-component glue, I glued the jar cap in the middle of the bottom piece. Then I glued a piece of aluminum foil (the kind you have in the kitchen) to the bottom part of the top piece. Note that I left some space there. This is where the perfboard with all the electronics is going to go.

To secure the perfboard to the lantern, I glued a set of four standoffs to it. A full standoff set costs a few bucks and will last you a long time. With the standoffs glued in place, I screwed in the perfboard securely, then attached all wires to their places. The hanging green wire you saw in a previous step is attached to the sensing plate with duct tape since I couldn't solder it to the aluminum foil. Finally, run the power cable through the hole we drilled earlier and connect it. Give the lamp a test go. The plate should be able to detect your hand even through the wood. If it doesn't hold it there for a few seconds and give it a few more tries. the chip has an auto-calibrate function so it may need some time to fine-tune its sensitivity.

This is probably the trickiest part of the entire project. Every side of my lantern is covered by what I'm going to call a "window frame". These are made of thin beams of wood that I also got from the crafts store. Each beam is 1 meter long and has a thickness of 3 by 10 millimeters. Four 1-meter beams are enough for a project of this size, but I got five, just in case. The individual pieces of the window frames were cut to size with a small hacksaw.

To ensure that each frame fits the lantern perfectly and doesn't fall off, I measured each individual opening and carefully cut each frame piece accordingly. I started with the bottom and the top pieces of the frame, which were as wide as the distance between the large frame pieces we already glued in. The tall side frame pieces were cut next: they were as long as the distance between the top and bottom lantern pieces minus 2 x 3 millimeters, which is the thickness of the frame. If you forget to subtract the thickness of the material twice, the window frames won't fit. Also make sure you glue the pieces correctly!

Then I cut the horizontal middle part of the frame: it was 2 x 3 millimeters shorter than the top and bottom frame pieces so that it could fit in between the side frame pieces. Finally, I cut the two middle vertical pieces of the frame. Again, make precise measurements and then make the cuts accordingly if you want these window frames to fit!

When your window frames are glued together, give them a coat of spray lacquer and let them dry. Leave one side untreated since that's where the paper is going to go.

From the hobby store I got what they called decoupage rice paper. It was translucent and had a cool look to it. A single sheet measures about 2/3 square meters and is more than enough.

Using a sharp hobby knife I made paper cutouts on my cutting mat. Then I glued them to the window frames using wood glue that I applied with my finger (because it is more fun this way). Since the paper wasn't blocking enough light, I used two layers on every window frame.

The last thing to do is to put on the window frames. Be gentle! They're made of thin wood and paper, after all.

And that's how my lantern came to be! It was a pretty cool project that helped me improve my skills, and I truly hope that you learned something new as well. If you have any questions, feel free to ask in the comments. Also consider visiting my YouTube channel for more projects and how-tos. Thanks!