Themed Lantern

I have always had an appreciation for theming and especially themed lighting. I always felt that themed lights serve a creative yet utility purpose for the environment that they accompany and serve as the perfect element that can make or break immersion for the space it occupies. I knew that if I was going to have a space themed basement some day, I would need unique lighting elements that were one of a kind.

Inspiration

I found inspiration one time when traveling to Galaxy's Edge in Disney World for a great lighting idea.

Throughout Galaxy's Edge, one may come across a number of unique lighting pieces that stand out. In one of the ride queues, this lantern sits atop a stack of crates and illuminates the room. I knew that this was a great element that brought immersion and story to each guest who passed it.

I made the decision to make a similar inspired lantern with few cosmetic and technical changes

Requirements

A few requirements that I wanted to set for this projects were the following:

I wanted to make my own inspired lantern, not create an exact replica.
The lantern needed to be portable (so I could theme my basement appropriately or remove them when necessary) .
The lantern light should be warm and dimmable for setting the appropriate mood and functional lighting.
The design should be modular and built with designs made by me and printed on my 3D printer.
I want the lantern to be usable for ~1-2 hours at a time.

Mechanical Design

All parts were designed in 3D modeling software and printed on my 3D printer. I decided to incorporate elements seen in Star Wars environments into the lamp design such as the interior of the death star. The lamp needed to dissipate the light in an even manner so the LEDs did not have high and low spots. For this, I purchased 3mm thick milky acrylic sheets and laser cut them to fit the appropriate holdings in the lamp.

The final parts were sanded, primed and painted with multiple colors to achieve the desired look of a device from a galaxy far far away.

Electrical Design

I next needed to look into the electronics for the lantern. This started with selecting what type of light I would use. I selected a 5V white light led strip since this would give me good lighting in all directions based on how I planned to lay out the strip in the center of the lantern. (see below)

I laid out the strip along the central column, pulled back the adhesive on the rear of the strip, and affixed it in place.

Once all strips were affixed, I began to solder the strips together in series to tie them to one power supply.

The arrangement of strips were done in a hexagon pattern to ensure uniform lighting in all directions when powered on.

The requirements above for portability required me to look into batteries. Not being a fan of alkaline disposable batteries, I opted for rechargeable 18650 batteries that would be sufficient for the LEDs. With each LED pulling between 20-30 ma of current, I had between 1.32 and 1.98 Amps being pulled from the lantern on max brightness. The 18650 batteries that I chose had 3400 mAh of capacity giving me ~1.7 hours of useful light on max brightness neglecting the efficiency losses from other devices in the circuitry. The time could be extended by decreasing the brightness of the lamp from its max output. This is discussed below in greater depth.

The requirement for dimming the lantern was next on the to do list. I first attempted to regulate the voltage going to the LEDs with a high rated potentiometer. This solution worked in short stints but soon realized that the potentiometer was having a good amount of efficiency losses in the form of resistive thermal losses due to the load of ~1.5 Amps.

Pulse Width Modulation (PWM) was the better answer for controlling the brightness of the LEDs. Pulse Width Modulation is a method of digital control that varies the voltage duration to deliver an average voltage (and current) to the system proportional to the duty cycle. By varying the voltage (and current) it is possible for the lantern to remain on for ~3-4 hours.

Example of Pulse Width Modulation from exploreembedded.com.

Lamp Base Electronics

Final Product

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