The Yogurt Lantern

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SammysHP
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The Yogurt Lantern

Introduction

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.

Design

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 Innocent, 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?

Edited by: SammysHP on 11/22/2019 - 14:03
CRX
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Could be a viable candidate for the Modified Light category as you made it yourself…

Firelight2
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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.

Muto
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Well done!

Good hand craftsmanship.

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TexasToasted
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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

SammysHP
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Thanks for your feedback!

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

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

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.

TexasToasted
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SammysHP wrote:
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. Big Smile
cu42
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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!

SammysHP
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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.

Luminosity
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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.

SammysHP
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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.

NWoodsman
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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 .