Three Ways to Integrate LED Light Into the Modular Lantern

After creating the modular lantern system, I experimented with different cheap ways to integrate LED lights into it and turn it into a decorative lamp. In this post, I describe the three ways I found the cheapest and easiest to implement that all create a wonderful result.

Preface

When I set up real light installations, I usually work with 24V DC power supplies that allow the power to be distributed over long LED strips with minimal loss. The downside is the required power converter that has its size and extra cost. It is a great solution for a permanent light installation in a house, and you always find a place to hide the installation.

Yet, while feasible, nobody likes to buy a power converter just to power a very short strip of LEDs in a 3D-printed lamp. So I decided to use 5V from USB as the power source for all three solutions. Meanwhile, USB cables are everywhere, and you likely have an old one you can reuse for this project.

If you like it fancier, many suppliers offer pre-made USB cables with a built-in switch. These cables have a USB-B connector on one end, a power switch in the middle and two wires at the other.

Requirements

• You need a 3D printer to print the additional parts.
• You need a soldering iron and soldering wire for all three ways and know how to use them.
• Depending on the implementation you choose, you may also need the following:
  • Leftover snippets of LED strips
  • Basic resistors.
  • A pair of matching connectors to allow solderless disassembly. E.g. reuse old fan connector cables.
  • 5V LED strips as described.
  • 5V RGB LED strips with individually addressable modules (WS2812B, “NeoPixels”, …)

Let us start with the cheapest way to make the lamp emit light…

Reuse LED Modules from an old LED Strip

If you ever did a light installation with LED strips, you may have some short leftovers that collect dust. Finally, you can make use of them, but wait, do they require 12V or 24V? That is no problem because you can use the single LED modules soldered to the strip. Usually, two or three LED modules are enough to create a sufficiently bright light for the lantern.

Unsolder the modules from the LED strip and solder them on a small board, as shown in the image at the beginning of this section; it requires some skill. If you have experience with electronics, it is no big deal.

Most white LED modules have a forward voltage of around 3V, which works perfectly with the 5V power from USB. You have to add approximately a 100Ω resistor in front of each module. I used SMD resistors, but you can also use wired resistors and point them down towards the opening of the cable.

I recommend you put a connector between the USB cable and the LED light – as neither the LED module nor the USB connector fits through the column of the lamp stand. If you solder the cable directly to the module, you will have to unsolder it every time you want to switch the side panels of the lamp.

In this section, I describe the cheapest way to install a light; therefore, the cheapest connector is made with header pins. I soldered a two-pin section of a female header pin row directly to the board.

At the end of the USB cable, I soldered a matching two-pin section of a male header pin row. I converted the pins into a connector with insulation tape and heat shrink tubing (now shown).

Alternatives

Instead of going through the hassle of unsoldering modules from an LED strip, you can use any spare LEDs you get hold of. You only have to consider the angle at which the light is emitted from the component you use.

The LED modules on LED strips usually have a wide angle, while the classic LEDs with lenses emit most of the light into a narrow area.

Print a Matching Diffusor

You need a diffuser to diffuse the light from the single-point sources towards the sides. On the printable project page, you will find a model that perfectly fits the requirements for a light source at the bottom of the lantern.

For a good diffuser, print model LR2268-61, which is a vase-mode print using transparent PETG filament:

The diffuser features various angles and gets narrower from the bottom to the top. That is all designed to catch as much of the light emitted straight to the top and redirect it to the sides.

The next way does not require skill… but probably requires ordering components.

Use a Short 5V LED Strip

An easier way to add light to the lantern is using a short piece of 5V LED strip. You may have some leftovers from a project you want to reuse or have to order a new one. Chinese stores, like the ones on Aliexpress, sell these 5V strips cheaply.

There are several criteria to consider:

The Type of LED Strip to Use

The following images show three different LED strips that have their benefits and downsides.

Using LED strips mounted in the way shown has the main benefit in that all light is emitted to the sides. If you use a lantern with side panels without holes, it already looks great without using a diffusor.

Closer-spaced LEDs, like the shown COB strip, will create a more uniform illumination. Larger-spaced LEDs require a diffuser for uniform illumination but also create interesting light effects on a wall if you use side panels with small holes.

Length and Power Consumption

Most USB power supplies deliver up to 500mA power to a regular USB-B connector. Therefore, your LED strip should consume less than this amount of power. If you buy strips with lower power consumption, you can wind longer strips around the cylinder and get more uniform illumination.

Usually, the seller will tell you how many watts a LED strip consumes per meter. Especially if you buy LED strips from Chinese sellers, never rely on these specifications and measure the consumption when you get the product.

If you read 15W per Meter, you can do a quick calculation. First, convert Watt into current:

Now, as you know the limit for USB power is 500mA:

The cylinder has a diameter of 20mm and, therefore, a circumference of approximately 63mm:

That would be a bit too short, as I recommend at least 3 full windings to create a good illumination. So we can do the reverse calculation. For example, we like to have five full windings around the cylinder:

So, if you like to have five windings of an LED strip around the cylinder, the maximum power consumption of that strip is approximately 7.9W per meter.

Yet, most manufacturers’ specifications are too high, and the product consumes less power than specified. The best is to measure the power consumption of the strip and shorten it until it is in the correct range.

If you do not need the full brightness, you can also put a resistor in front of the LED strip to reduce its power consumption. Please note that the most common resistors are rated for 5W and unsuitable for this task. You will need a beefier 10W or 15W resistor in the range of 5-30Ω.

How to Build this Solution

Start by printing the cylinder on which you will stick the LED strip — print model LR2268-71 as described. Meanwhile, prepare the LED strip and all connections.

Start by cutting the LED strip to the correct length.

Measure and cut a piece of a short cable that fits in length from the top to the bottom opening in the stand, as shown in the picture above. You can reuse any cable with at least two different wires in its core. I used a cable with four lines and cut off two at the ends.

Solder the cable to the USB strip, and remember which wire you used for the plus and minus connector at the LED strip. Best use a red write for the plus and a black one for the minus connection.

After that, I used heat shrink tubing and insulation tape, as shown in the image above, to connect nicely to the strip.

Then I solder the connector to the other end of this cable. As the connector I used had three pins, I also soldered a third wire to the connector for stability. It has no function here, as this wire isn’t connected to the LED strip.

After soldering the wires together, I used insulation tape to keep them separated. Again, I first slid some heat shrink tubing over the cable to seal off the solder joints and create a nice and strong connection.

Next, I cut off the MiniUSB connector from an old USB cable. These cables have four wires, but you only need the red and black ones. The red wire has the +5V, and the black is GND. Either cut off the unused wires or connect them with a 100Ω resistor. The 100Ω resistor will signal that you use the cable only for power, not data transmission.

Solder the matching connector to the end of the USB cable, similar to what you already did with the cable from the LED strip. Now you can test if the LEDs light up when you connect the USB cable to a charger or if your wiring has a problem.

When the print of the cylinder finishes, slide the beginning of the LED strip into one of the slits and wind it around the cylinder. No matter how many windings you do, ensure the spiral is well spread over the available surface.

Now stick the cylinder with the led strip into the stand of your lamp. In the photo above, the lantern itself is missing; you should do it with the fully assembled lantern.

Connect the USB cable with the cable from the LED strip and slide it through the channel at the side.

I created a new foot part version, LR2268-45B, which has grooves and alignment holes for attachments. If you printed this version, you could also print one of the lids: LR2268-48A or LR2268-48B and seal off the open space in the stand.

Print a Matching Diffuser

As the LED strips already emit light to the side, the best is to print the diffuser model LR2268-62.

It uses the “fuzzy skin” feature of the PrusaSlicer to create extra diffusion.

The image above shows the diffuser with an LED strip of only 60 LEDs per meter.

The additional diffusion of the lantern sides creates an equal illumination of the lantern.

If this was too simple, check out the next section.

Almost like a Real Candle with a Strip of WS2812B RGB LEDs

If you like your lantern to look like there is burning a real candle inside, you may like this last version of how to install lights.

Requirements

• A short strip with WS2812B (or -A) or compatible LED modules. Sometimes, they are called “NeoPixels”.
  • I used a strip with 74 LEDs per meter.
• A small and cheap microcontroller (ideally with 5V output):
  • Adafruit Trinket
  • Seeeduino XIAO
  • DFRobot Beetle
  • Adafruit Feather
  • Arduino Nano
• USB cable that powers the microcontroller board.
• A cable with at least three wires, two power wires and one data wire.
• A matching pair of three-pin connectors to make disassembly solderless.

Downloads

Download the 3D models and the firmware here:

How to Build

Follow the instruction of the build with the regular LED strip, but use an extra line for the data input of the WS2812B based strip.

• Ensure the LEDs build columns and rows when you wind the strip around the cylinder. With my 72 LEDs/m strip, I created four rows and five columns with LEDs.
• Also, build the connector pair with an additional data line.

• Attach the +5V line directly to the USB power line on the microcontroller. Most microcontrollers have a pin called USB that is directly connected to the USB power source.
• Attach the GND line with the GND of the microcontroller board.
• Attach the data line to a suitable digital output pin that is not shared with another function. If the microcontroller’s digital output is 5V, add a 100Ω resistor between the controller and the LED strip on the data line. If the digital output level is 3.3V, connect the line directly.

• Now, install the “Adafruit NeoPixel” library in the Arduino IDE and open the downloaded firmware.
• In the file Configuration.hpp, change the cLedPin value to the pin you used for the data connection.
• If you have more or fewer rows and columns, as shown, adjust the values cLedRows and cLedColumns.
• Compile and upload the firmware to your microcontroller.

The LEDs should now show a candlelight emulation. 🎉

Conclusion

If you have questions, missed any information, or wish to provide feedback, add a comment below or send me a message.

Happy printing!

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