My dad is a neurologist, so I made this lamp as a whimsical Father's Day gift for him. To get a more modern and universally appealing look, you could do something like this with a different concrete shape, using a plastic bowl to get a half sphere, for example.
Be sure to check out the full build video on my YouTube channel (video link above) and subscribe if you like it.
Step 1: Gather the Materials
You can mix your own, or use any store bought concrete mix. If using pre-mixed, I recommend Quikrete Q-Max or 5000.
1. Bag of Medium Grad Quikrete sand
2. Bag of Portland Cement Type I/II
3. Sika Concrete Bonding Agent & Fortifier
4. AR Glass Fibers (optional)
5. Silicone Cake mold (brain shaped)
6. 16 mm LED latching on/off button
7. SK6812 LED strips (you can use any strip you like, but I recommend getting one that has 60 or 144 leds/m)
8. RF LED controller and remote (a RF cheap one for $5-10 works fine)
9. power supply (I bought a 2A 5V power supply, to match the 5V SK6812 LEDs)
10. Scrap wood, total size about 3' long x 6" wide, I used some walnut I had leftover from other projects. You could use whatever you like, even plywood. But
Step 2: Make the Concrete Brain
For my mix I used sand, portland cement, and acrylic bonding agent/fortifier in a 4:4:1.5 ratio (so for ~9 lbs, I used 4 lbs of sand, 4 lbs of portland cement, and 1.5 lbs of acrylic fortifier).
I mixed up the portland cement and sand, then added it slowly to a bucket with the pre-measured acrylic fortifier. I then spread a thin layer of it in the mold as a face coat, and let this set up for a few minutes. I added AR glass fibers to the rest of the mix (just a couple handfuls - I wasn't too precise), although I think this probably wasn't necessary. After adding fibers to the mix, I filled in the mold by hand. If you have some superplasticizer, adding a bit can make the back coat flow a little better. (Home Depot sells packets of rapid set plasticizer, so sprinkling in some of this would do the trick.) Let this cure for 24 hours, then de-mold.
Step 3: Make the Wood Base and Post
Essentially you are just building a box. In the top, you'll cut a slit for a plank to slide through. The size of the box and post don't matter too much, just make sure your post isn't so high that the weight of the concrete brain causes it to tip over. I cut mitered corners and glued it together, using painters tape to hold the box in tact while the glue dried.
After the glue dries, cut a 5/8" hole for the on-off button, and a 1/2" hole for the power plug, in the base box.
Then cut a hole about 2/3 of the way up the back of the post, and cut a channel running up the back of the post to the hole. This channel and hole will be used to hide the wiring from the LED strip to the electronics in the base. To cut the channel, you can use a router, or use repeated cuts on a table saw, with a stop block so that the channel doesn't go all the way through.
The plank you are using as a post should have a small piece glued to the top (see the pictures), to offset the concrete brain from the post. This offset piece serves two purposes: (i) the concrete brain will be attached to it, and (ii) the LED strip will be wrapped around its edges, hidden behind the brain. Size this offset piece so you have about 1/2" to 3/4" inset from the edges of the post, to allow room to hide the LEDs.
Now put the post in the hole, and patch up any imperfections in the edges with wood putty (I used Timbermate walnut colored wood putty). Let the putty dry, sand everything down and apply finish. I used two coats of natural danish oil.
HINT: If for some reason you get the whole thing assembled and it isn't steady (because the concrete makes it top heavy) you could always mix a bit more concrete and pour it in the base to weight the lamp down.
Step 4: Attach the Brain to the Post
In the pictures I did this before I put the post and base together, but I'd suggest doing it afterwards. To attach the concrete brain you will use Tapcon concrete screws.
First pre-drill four holes through the post and offset piece using a standard wood drill bit. I used a countersink bit so the screws would be recessed. Then switch to the drill bit for the Tapcon (it comes with the screws, usually). Use the pre-drilled holes on the wood as a template to mark where matching holes should go on the back of the brain, and then drill the holes in the brain. Then use a shop vac to make sure all the dust is vacuumed out of the holes (this step is very important for the Tapcon screws to work properly). After cleaning out the holes, screw the brain to the post.
Step 5: Wire the Electronics
You could greatly simplify this if you don't want a physical on-off button. In this case, you could use a standard LED strip kit with controller, power supply, and strip, and just solder extension wires from the LED strip to the controller, so it can be hidden in the base.
To add the power button, just wire your power jack to the button, and the load on the button to the LED controller. This way you can control it with the physical on-off button, and change the color or light pattern with the RF remote.