In this video, I will show you how I created this rather interesting looking, metal construction which is in fact a persistence of vision RGB LED Globe.
That means we've got 38 addressable RGB LEDs in total, which rotate rapidly in a spherical shape in order to create an optical illusion which manifests itself as a complete spherical picture.
This way you can create an intriguing looking eye catcher by utilizing different shapes and colors, or even write letters with it.
So, let's not waste any more time and let's get started with the build.
The plan for the mechanical construction is rather simple.
For starters, we need a DC motor which rotates with a suitable speed.
I went with this 12 volt, 7 watt, 3000 rpm one which, according to simple math, should rotate up to 50 times per second.
Which is definitely fast enough for our illusion.
Next, we need an adapter that connects the six millimeter shaft of the motor to the eight millimeter metal rods.
Such adapters can often be salvaged from 3D printers.
Only problem is that they are semi flexible.
So due to this fact, and also to stabilize the rotating components, I added a metal support construction consisting of a steel base plate and two pieces of flat steel in combination with a ball bearing.
To finalize the plan, I added a 3D printed circle and a 3D printed cuboid to the later rotating metal rods.
This circle will house the LED strip, as well as the hall effect sensor, and the cuboid will, therefore, house an Arduino along with a LiPo battery and a suitable charge protect boost circuit to provide 5 volts for the system.
And now that the plan is complete, let's get to the practical part.
I started off with this steel base plate which had a width of 20 centimeters as well as a height of 20 centimeters and the thickness of 2 centimeters.
Through the help of my metal ruler, I marked its horizontal and vertical center lines in order to determine the exact center of the plate.
Then, I unscrewed the two bolts that held the motor together and removed the lower part of it, which contained the characteristic carbon brushes of a DC motor.
I positioned this part of the motor on the center point of the steel plate and used it as a template to mark the two screw holes of the motor onto the plate.
By using a prick punch, I created deeper indentations into the material and, afterwards, used them as a guide to create two holes through the material with a 4 millimeter drill bit.
After making sure that the bolts of the motor, pushed through the newly created holes, would align with the previously utilized templates; I grabbed a 9.
5 millimeter drill bit in order to Increase the hole diameter.
But only up to a depth of around 5 millimeters.
This way a self-locking M4 nut could sit flush with the surface inside the indentation.
Now, before securing the motor to the steel plate though, I had to mount metal brackets to the plate as well.
For that, I marked the center point of its width, aligned it with the horizontal center line of the plate on its left side, marked the two mounting holes, and then created them with a 5 millimeter drill bit.
After, once again, enlarging the hole partly with a 9.
5 millimeter drill bit in order to, this time, accommodate the bolt heads; I secured the brackets to the plates with two M5 bolts and self locking nuts.
Next, it was time for the flat steel, which had width of 4 centimeters, a depth of 4 millimeters and a height of around 50 centimeters.
I simply leaned it onto the brackets, secured it in place with a clamp, and marked the position of two mounting holes onto it.
After, once again, enlarging the indentations for the holes and drilling them with a 5 millimeter bit, it was time to come back to the motor.
As you can see, it was no fun inserting the rotor in between the carbon brushes.
But once they were connected, I pushed the two halves of the motor back together.
Now to finally mount the motor to the steel plate, I utilized an M4 threaded rod.
After marking a length of 8.
5 centimeters on to it, I created two pieces of this length, through the help of a simple handsaw and then added an M4 self-locking nut to one end of the two pieces.
This way, we can insert the threaded rods through the center mounting holes, push the motor onto them, screw them in place, and finally secure them once more with another self locking nut.
Next, I secured the adapter to the shaft of the motor and got myself an aluminum rod with a diameter of 8 millimeters, which I mounted to the other side of the adapter.
At this point, I created a 3D model of the circle and the cuboid with the 123D design software and printed them both with my Delta 3D printer.
The results were certainly not perfect, but definitely good enough for this project.
So, I slipped the circle onto the aluminum rod and marked height of around 4 centimeters above it, at which we can cut the rod.
After reinserting it into the adapter, it was time to temporarily secure the flat steel to the side of the steel plate in order to mark a spot onto it 2 centimeters underneath the top of the aluminum rod.
I then cut the flat steel at this indication point, and continued by marking mounting holes for a second bracket onto the other end of the flat steel.
After creating the holes, the same way I described it dozens of times already, I mounted the bracket temporarily to the flat steel, in order to position it on top of a second piece of flat steel to once again mark the holes and then drill them.
This way, I connected the two flat steel pieces together through the brackets and then mounted this newly created construction to the side of the steel plate.
Next, I utilized my metal angle by positioning it exactly on top of the middle line, and transferring this line onto the stabilization construction.
So, after removing this top flat steel piece, and marking the center point of the newly created line; I utilized it as a guide to drill a hole with a diameter of, firstly 5, and then 13 millimeters.
But since that was still too small for the ball bearing, I got myself a step drill and started enlarging the hole even more.
Only problem was that I quickly drilled into the surface of my table.
So, I was forced to enlarge the hole up to a diameter of 22 millimeters with a hand drill.
Now, the ball bearing did not fit easily inside this hole.
So, I grabbed one fresh from the freezer and hammered it into position.
At this point, I removed all the temporary bolts and nuts, and replaced them with shorter bolts and the corresponding self-locking nuts.
And after adding the top flat steel piece, inserting the aluminum rod into the ball bearing, and sliding the circle, as well as the cuboid, onto it; the only thing left to do for the mechanical bolts was to mark the mounting holes for the circle and the cuboid, and create them slowly and carefully with a 3 millimeter drill bit.
The last thing to do was to, once again, slide the pieces onto the aluminum rod, secure them all with M3 bolts and self locking nuts, and supply power to the motor wires to take it all for a little test spin.
As you can see, it rotated pretty fast and, more importantly, without vibrating too much.
Which means, it was time for the electronics.
There are actually just a few components we need for this project.
The first one, and probably most important one, is an APA102 LED strip with a density of a whopping 144 LEDs per meter.
After partly peeling off its protective tape, I additionally used a bit of hot glue on one circle half, in order to properly stick the LED strip onto it.
And once I was close to the top, I cut the strip, soldered a the wire to each one of its contact points, and afterwards glued the rest of it onto the circle.
Next, I soldered a wire to each lead of the U18 Hall effect sensor, marked the middle point of the circle half without LEDs, and utilized hot glue to secure the Hall effect sensor in this position.
After also gluing its wires to the circle, adding a magnet to the flat steel close to the hall effect sensor, and hooking up a pull-up resistor, and powering the sensor; we can see that it changes its output state whenever it passes by the magnet.
We can use this indicator later on to properly display images with this POV system, but, for now, I secured the wires to the rod with zip ties and soldered all the data wires to the Arduino according to my finalized schematic of this project.
Which you can find, as always, in the video description.
To power the system, I got myself a 1, 100 mAh LiPo battery; to which, I glued my homemade charge protect boost circuit, which I will show you how to make in another video.
After soldering the battery wires to its terminals and hooking up its output wires to the oscilloscope, we can see that, by flicking its power switch, it creates a stable 5.
And in case you don't have such a circuit, you can also use a TP 456 in combination with a boost converter as a replacement, it's just a bit more bulky.
Anyway, after soldering all the power wires together and using shrinking tube to protect them from shorts, I uploaded a simple test sketch to the Arduino, flip the power switch, and realize that everything works like it was supposed to.
So to seal the deal, I use duct tape to firstly, secure the battery with power circuit to the cuboid, and then secure the Arduino to it as well.
And at this point, the hardware part of this project was complete, and it was time for another test run.
Which showcased that, even at a motor input voltage of 5 volts, this system was mechanically not very stable, and anything above 5 Volts would have led to certain destruction.
I think it would been a good idea to add a second flat steel on the other side of the system, but, nevertheless, the light show was still pretty amazing to look at.
So I created another piece of code, which pretty much only cycles through the different colors.
But even something as simple as that already looks pretty awesome.
But keep in mind that the camera can't do it justice here, since it introduces weird flickering, which you normally cannot see with the human eye.
Another sketch that I created stores boolean values in different arrays in order to create letters, which also worked out pretty well with the LED globe.
Now, I'm definitely not the best animation creator / programmer; so, I hope you give a project like this a try and create / share your artwork along the way.
As always, I hope you enjoyed watching this video.
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Stay creative! And I will see you, next time!.