This is project that came to me a while ago, when i moved to my current house. I am a college student , so when i went to the store for a lightbulb and a light shade, upon seeing the price i thought " Hey, with the things i have laying around i could make a ceiling light for way less money". So i went back home, assured myself i had everything i needed and jumped straight to the drawing board.

In short : The light was finished within a weekend , total cost for someone without any spare parts is probably under 10€ going down the more spares you have (i spent 1,30€) , the room needed no modification and illuminates my whole room (is used as study light too) with a consumption of less than 12 Watts.

Step 1: Parts Evaluation

The first step was to look at the big picture and come up with thebasic parts.

Cardboard: easily found for free as big cardboard boxes from appliances packaging , cut it to big squares.

Led Strips: Fortunately for me i found some used white led strips for free. If you have to buy it an indicative ebay price is 2,50€/meter or 8€/5meters .

Power Supply: Calculating the minimum required PSU is very important and there are numerous formulas online to do so. I had a spare 1A 12V transformer which is way more than enough. Generally 12V 1A would be sufficient for our cause, Indicative ebay price 3€ .

Wire: Just some scrap laying around wire will do for jumpers.

Glue: Because chewing gum wont do the job. Indicative price 1,30€ .

Mains cable connector: connect the mains to our project.

Tools

Screwdriver

Sharp blade cutter

Soldering iron

Pencil

Metric tape

Ruler with 90 degree angle

Double sided tape (for used led strips, for new ignore it )

Step 2: Drawing and Positioning

Positioning

When electrical engineers make the electrical plan of a house, as a rule of thumb, position the ceiling light line at the center of the room for optimal coverage.
UNFORTUNATELY my landlord thought it would be a great idea to build a huge wardrobe at one side of the room. Therefore, my little project cannot be positioned at the center of the room (that would cause trouble with opening the wardrobe and also would be aesthetically ugly), so im recalculating the center of the space which is defined by the wardrobe and the walls.This means that somehow the light must be hang by the edge rather than the center of its gravity. The problem is solved with a rope supporting the opposite edge to the main cables and placing weights apropriately.

The space now measures 2,6m x 3,5m forming a rectangle. BUT we must also calculate its center coordinates .The center of rectangle is the mid point of the diagonal end points of rectangle. Refer to the image.

Going to the center is unachievable, yet getting as closee as possible is our goal.

For everyone else, finding the center of gravity of the light and positioning the support ropes there should be enough, extra support to the edges can be added.

The light

Time for us to leave the big picture behind and make things specific. We are kind of 3D printing cardboard, positioning and carving layer by layer. I chose a rectangle shape for numerous reasons ( led strips are straight, easy to handle and create, strict yet contemporary shape, proportional to the room ), but you can leave your imagination free here. I also cut some curves at the bottom piece to make it a bit fancier.

The bottom piece has a size of 70cm x 52cm which is the proportions of the room divided by 10 and multiplied by 2. Then it is divided into parts vertically and horizontally 5cm apart each ,with a curved free hand line reaching the meeting point of the centers axis and the last line.
The next pieces will have a width of 15cm so as to extend 5 cm at the outer edge and yet be able to support the next layer.

⦿ First layer: curved rectangle piece for decoration.

⦿ Second layer: solid cardboard sheet.

⦿ Third layer: we put cardboard strips along the edges with a width extending 5 cm outwards and leaving enough space inwards for 2 led strips at the previous piece. The last layer will have the angled leds put at its back, away from the edge.

⦿ Support points: the third layer will host four holes trough which two ropes are going to go through, in order to support the weight of the opposing sides of the rectangle.

⦿ Fourth layer: Angled pieces are placed on the back of this layer.

⦿ Inbetween layers: Between each layer i have placed small cardboard pieces to make the shapes stand out a bit more and allow light to go through the gaps.

Step 3: Building the Cardboard Frame

We begin by carefully measuring the bottom piece and cutting clean to proportions, finally mark the curve and then cut it out.
This piece is very important , because it will now be the base on which we are going to overlap the next cardboard pieces and also has the higher visibility, with a decorative purpose.

The second layer is just an identical piece without the cuts to bring the light to rectangular form. Between the first and second i added some scrap pieces as i mentioned earlier.

Notice how from this point up we dont use the whole sheets, rather than strips of cardboard positioned on the edges of the previous piece. This will create the space needed for the power supply, but also "stairs" for maximum number of led strips .

After finishing the basic patern it is time to add some inclined cardboard pieces. Their purpose is to help the leds shine their light in a different angle, making the most out of them , while at the same time preserving an ambient character. We make these by scoring the cardboard on one side and bending it, then gluing .

Finally four holes are punched in the third layer and ropes are pushed through.

Step 4: Adding Electronics

Prepare the mains cables by cscrewing the connector and adding electrical tape where necessary.

Time to peel the sticky tape from the led strips and put them on the cardboard. Because im using scrap led strips ,i had to cut new pieces of double sided tape, but this will not affect most people.

Now the most tiring task, connect all the led strips in parallel with small pieces of wire running along the cardboard but also up to every level.

Finally place the psu on the cardboard base and connect all the power rails to it. Test it to make sure everything is sparking up.

Step 5: Installing on the Ceiling

Great we have our lamp, everything is ready and we have to install it.

CLOSE THE MAIN POWER SWITCH BEFORE DOING ANYTHING ELSE.

I am not responsible for any harm that may occur if you are stupid enough to touch high voltage cables , without first shutting down the power at your home.

I used some scrap high voltage cable, screwed the one side to the connector and soldered the other to the transformer, also not shown in the pictures i secured it with electrical tape to avoid short circuits, or someones death.

Good job, we are done !

Time to turn the switches on and evaluate the aesthetics and usability of the light.

Step 6: Closing Thoughts and Future

This was a fun build , even though it didnt turn out as cool as it was in my mind . The hardest part was handlind cardboard which turned out way less forgiving than i thought. Also i must mention that connecting all these strips in parallel was a true torture, yet i fell it was worth.

As a future improvement , the psu will be used to power a microcontroller, therefore allowing for RGB mood light usage and wireless control of the light and its colors. Serving also as a wake up light simulating the sun is an interesting idea.

I hope you enjoyed this as much as i did, if so dont be afraid to give it a chance.