The Yogurt Lantern


I haven’t ordered a LT1 yet and I don’t know if I will ever do. I don’t need a lantern that often. But sometimes… So I thought a diffuser should be enough. You can get simple plastic or silicone diffusers from China cheaply, but I didn’t want to wait and wanted something better. So I created my own diffuser.

Please note that this is not a submission for the Old Lumens BLF Self Built Flashlight Contest because it it not a complete flashlight, just an accessory.


While most simple diffusers are just like a sphere or a cone that diffuses the light in all directions, my idea was to use something similar as the LT1 that does not emit light upwards, but more usable to the sides and downwards. That’s why the LT1 has the LEDs at the top (which adds some complexity and increases manufacturing costs). For my design I wanted something more simple and universal, using an existing flashlight.

So I came up with this design that uses a reflector at the top which reflects the light from below to the diffusing material.

This example (and my prototypes) uses an Emisar D4S (SST-20 4000K) as the base and as the light source.

First (5 minute) prototype

To test the feasibility of this design I made a paper prototype using a throwaway plastic cup (soon extinct in the EU), aluminum foil and some paper (of course!).

Please ignore the purple tint! The camera (app) of my phone has some issues with low light.

Second prototype

So today I bought a small cup of yogurt and a box of something that I probably should not eat all at once O:), because it has a reflective coating on the inside (not perfect, as I will explain later). I won’t go much into the details of the build, but most of it is self explaining.

Cut a circle out of the bottom of the cup so that it fits tightly on the flashlight. Next cut a circle from the box (nom nom) and cut a line from the center to the outside, so that you can roll it into a cone. I used a stapler to connect the overlapping parts, but before you start, test it to find the correct angle! Then cut it to size and use some tape to attach it to the open end of the cup.

And this is the result!

And now with aux LEDs.

I’m rather happy with the results. The plastic cup is too thin and flexible for every-day use. The material that I used for the reflector is slightly translucent, so it does not reflect all light. Also make sure to not use the FET range of the flashlight! This traps heat and will melt!

Future plans

3D printing it? Bayonet attachment for adapters to use it with different flashlights?

Could be a viable candidate for the Modified Light category as you made it yourself…

Looks great.

Much easier to machine than the BLF lantern and no need for a gigantic heavy heatsink at the top. Instead this is just a diffuser with reflector that slips on to an existing light.

Well done!

Good hand craftsmanship.

I’ve been thinking along the same lines as you, but I’m going to try a polished stainless half sphere in the top to see how that works.
Aliexpress stainless 1/2 balls

Thanks for your feedback!

I will document the next prototype better and think about submitting this thing to the contest. :slight_smile:

Initially I had this idea as well, but then I simulated the light path and realized that it doesn’t work. Too much light would be reflected to the top. My cone has an angle of about 5-15°. You have to play with it to match it with the cup.

I had to read that a couple of times for it to sink in, but I finally got it. :smiley:

I have tried some different hand made top reflectors also. I think the cone works better then the half sphere myself, but this has much to do with the throw, reflector etc. of each light. I am no engineer so I am curious how this goes!

Here comes the next version of the Yogurt Lantern with better materials, but still a prototype.

The material that I used does not reflect 100% of the light. With a better material the efficiency could be improved.

Cut out a small section to form the cone. You have to experiment with the angle to optimize the reflection angle. I used some tape to connect both sides.

Before gluing everything together I added a magnet to the inside of the lid. The plan is to attach accessories like a lampshade.

Hank should build this as an accessory to the D4S. The lantern shade could have threads at the bottom that match the D4S bezel threads. So when you want to go camping, you take off the normal bezel and screw on the lantern shade.

That would make a modular, but sturdy light system. And by having the shade firmly attached, you could add a bail handle to it for carrying.

Instead of switching it with the bezel each time I would design a new bezel that can be kept screwed on, but has a bayonet connector for the diffuser.

I found a better more permanent option: Sili-pint drinkware is pure silicone and makes a beautiful frosted version of their products that would be perfect for a lantern. I might order the half-pint size to try as shown on their products page here for drinkware .

Next level. I got myself a 3D printer and guess what… :person_facepalming:

With the help of some self-adhesive mirrored foil:

The yogurt cup clips into the reflector lid:

And the result (mostly the same as the previous build):

If someone wants to build this as well, here’s the STL. But please note that it requires the exact same yogurt cup, 75 mm diameter, rim roughly 0.8 mm thick, about 75 mm in height.

Nice work! :sunglasses:

You haven’t seen my latest improvements yet! This is the current state of the Yogurt Lantern:

First I’ve printed an adapter ring for better fit between the yogurt cup and the head of the D4S:

It is a really tight fit. It needs some improvement so that it is not held in place by friction fit but some kind of clips or springy parts. Not easy with just 3D printing because of creep. Maybe other material than PLA or spring steel strips.

The second improvement is a stand inspired by Cggzilla’s stand for the LT1. It has a cutout for the lanyard.

In my first iteration I’ve added a small ring so that it makes only contact with the ground only on the outer rim. This prevents wobble on not perfectly flat surfaces. Sadly it was too slippery.

So I removed it and used some foam with double-sided tape:

Same issue: friction fit. I really need to find a design pattern for such parts. Any ideas?

And to finish this post some action shots.

If you want to try it yourself, here are all STL files. Still the same limitation: You’ll need a yogurt cup with the same dimensions.

Thanks for the info, but I don’t have a 3d printer. If or when I get access to one I’ll definitely check it out in more detail.

The basic design is optimized for low-cost building without special tools. The 3d printing part makes some parts nicer, but doesn’t affect functionality. Everyone can try it, it’s fun project. Maybe we’ll see some good improvements.

Very nice work, mate. Very inspiring, but I don’t want to go the path of buying a 3D printer.

With torches and nixie clocks I already have expensive obsessions now. :smiley: