Introduction: Concrete LED Light Cube

About: Hi I'm Linn and on my Youtube Channel I have lots of great videos about building, construction and fun projects. You can also check out my site @

This concrete LED light cube is very simply, yet pretty striking and I think it would make the perfect accent or night light. Concrete is so much fun to use, and of course you can vary the design depending on your preferences and add color, change the size of the molds - whatever. It's a pretty easy project and you don't need too many tools to work on it!

Step 1: Electronics

For this project I'm going to be using these 5 volt led strip lights. These are really cool because you can power them with a common 5 volt phone charger. Here's a regular 12 volt led strip on the right for comparison, and there we have three lights in series and every connection is a parallel connection, whereas on the 5 volt strip they are all parallel with only one light and resistor per section.

Step 2: Micro USB

I'm going to be using a micro usb, and these are really tiny. This is what you need so you can plug any phone charger in. Now, these have multiple pins because the middle ones carry information, but I only have to concern myself with the the ones on the ends which are positive and negative.

First of all I'm soldering the micro usb to some wire to connect to the lights, and they are so small and difficult to see! Took a little while to get that right. But this is what it looks like all connected.

I'm also putting on some shrink wrap to completely protect the connection and the wire - cause this is going to sit inside the concrete!

Step 3: Lexan

OK, next up I'm cutting up some lexan into strips, and this is for the middle section of the lamp. I made them 1 1/2 inches or 3.8 cm high, and totally the lamp will measure 3 1/2 x 3 1/2 x 3 1/2 inch (90 x 90 x 90 mm). To frost the glass, I sanded the pieces with fine sandpaper, but you could also spray with frosted spray paint. Then I mixed up some epoxy and glued the sides together to form a square.

Step 4: Molds

Now, let's move on to the concrete molds. I'm just using some scrap plywood here, so I've got some pieces cut up which I'm just drilling and screwing together. To protect the plywood from the moisture and make it a little easier to separate from the concrete I spray painted them with som glossy paint.

Step 5: Concrete

Time to mix up some concrete! But first, remember this little micro usb wire? I'm putting some tape on the connection end to protect it.

Then I'm mixing up the concrete, and this is actually mortar mix which is smoother than traditional concrete and doesn't have the gravel and stones in it.

Step 6: Assembling the Blocks

So I've got two molds, one for the top and one for the bottom. First putting down a layer of concrete. Then laying the usb wire down flat, with the tape covered usb opening against the plywood. Then I put on some more concrete on top to fix it in place, and cover up to the edge, but I made sure to have the wires point up straight in the middle.

Then repeat with the top mold, which is the same but without the wire.

Once dry, I unscrewed the molds carefully, and pried the bottom plywood apart, and I had my blocks.

Step 7: Testing

Now I actually did this multiple times, experimenting first with different wetnesses, and I know dry concrete is supposed to be stronger, but I liked the wetter concrete more in terms of looks, a little smoother.

On my third attempt here, I also placed the lexan square in the wet concrete to create an indention, and that made the plastic square fit better once dried without many gaps.

Step 8: Sanding

Once I had the blocks, I sanded them - first I used a sander, and the dryer blocks needed more sanding. But then I moved to sanding by hand - and I also found that the blocks made with wetter concrete didn't need nearly as much sanding, they were pretty smooth already, apart from some sharp corners.

Step 9: Connecting the LEDs

OK, now the next step here was to solder on the led strip to the wire coming up from the concrete. And just testing here to make sure everything works. Now to secure the lights in the middle of the block, I simply used hot glue and I kind of glued the strips on top of each other into this tower thing. And then just putting it all together.

Step 10: Bottoms

To make sure the concrete bottom doesn't scratch a table surface I'm cutting out some rounds out of leather for feet and then just hot gluing those on as well.

Step 11: Frosting

I also cut up some paper that I glued on the inside of the plastic square, and this is because I didn't actually want to see any of the individual lights, and the paper dimmed it even more so there was just this glow.

Once everything looked good, I epoxied the plastic square to the concrete pieces. I also put some shellac on the concrete to seal it.

And there it is. To turn the light on, you can either plug in a 5 volt power bank to make it portable and use anywhere, or you can plug in to any standard phone charger or your computer.

Step 12: Conclusion - Watch the Video

For a much better perspective, make sure to watch the video to see all the steps in detail and the finished result.