Spherical LED Matrix - Sphere Shaped LED Screen From LED Pixel Strip

A project a long time in development, while the physical design is relatively simple, the method of control is a bit more complicated and required the development of suitable software and techniques. This project is based around a 20" diameter diffused acrylic lamp cover that was purchased from a building materials recycling company. It either hung or was mounted on a pole and contained a high wattage mercury bulb(it seems). It was already separated in two pieces, top half(hemisphere) and bottom half(hemisphere) with the mounting hardware. The acrylic bottom is held onto the metal base with a metal flange that bolts together from the outside and clamps the bottom hemisphere between them. The resolution is 68 x 24 with a total of 1238 pixels worth of LPD8806 LED strip was used, while using flat LED strip caused some problems, there really isn't many other options that wouldn't require some serious design and manufacturing. Which for a single shot, DIY project like this, isn't an option.

While several variations of LED spheres can be found on the internet, they either have a rotor with LEDs on it that spins quickly to produce the effect or are made in sections of injection molded parts, which would is very costly and complicated. While this design took a lot of tools to complete, the cost, overall complexity of the system is low, along with being quite sturdy.

Since the completed project doesn't really have a sharp display with some variations in LED spacing and positions. It is more suitable for abstract patterns and colors, rather than detailed content. But can do text scrolls and other effects well enough.

See the webpage at: http://www.nledshop.com/projects/spherematrix/

sphere-project-files.zip
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Step 1: Tools and Supplies

Hardware Supplies:

Diffused acrylic globe with base, in two hemispheres - Found a 20" sphere from an industrial light at a salvage/reuse yard.
1/8" aluminum bar, 3/4" or 1"
Heavy gauge metal strapping, 20ga or thicker
Threaded Rod
Bolts, Washers and Lock Washers for the threaded rod
LED Pixel Strip, choice of chipsets and densities, used here is LPD8806
Base plate, 8" disc, something strong like marine grade plywood or aluminum
(Optional) Matte Black Vinyl Cut strips with cutouts for LEDs

Electronics:

LED Pixel Strip - WS2801, LPD8806, APA102(best), WS2812B(not recommended), used here is LPD8806
LED Controller - Used here is a modified NLED Pixel Controller Ion(USB), Or Pixel Controller Mini, Pixel Controller Micro, Pixel Controller Electron(USB)
4 Conductor Ribbon Cable, 22 AWG
16 AWG Power Wire, 2 colors
2 Conductor stranded wire, red and black
22AWG solid strand, 2 colors

Tools:

Soldering Iron and Supplies
Misc Pliers
Tin Snips, to cut the metal strapping
Power drill and bits
Hacksaw, sawzall with metal blade for cutting aluminum bar
Pop Rivet with 1/8" x 0.25" rivets
Table Saw for dado cuts on base plate
Ring Roller - Gear Driven Ring Roller, Harbor Freight Tools SKU: 36790

Software: Covered in Step 9

Step 2: Layout and Planning

By far the hardest part, anything round is difficult to do by hand. And even more difficult to plan. The idea was to have the support structure for the LEDs 1" away from the acrylic shell. The distance was chosen through experimentation. Since the LED strip wants to be flat, it was assumed that forcing it into a round shape would cause the LEDs on the strip to not all point in the correct direction, varying slightly. The 1" distance was a compromise between a sharp pixel and hiding the misdirected LEDs. Overall a good choice as it ended up with pretty good resolution and hides the imperfections from the LED placement.

Started with completely taking it apart and measuring.
Laid it out in CAD(or Adobe Illustrator or something)

Step 3: Part Assemblies

Base Plate:

Used a scrap piece of marine grade plywood that was big enough to cut a 8" diameter disc from.
Find the center for the disc and drill a hole just large enough for the threaded rod.
Cut a perpendicular dados using the center hole as the center. The dados were as wide as the aluminum bar. Which was 3/4", and 1/8" deep, same as the aluminum bar. The tighter the fit the better.
Using the removed flange(that mounts the bottom acrylic shell to the base, marked and drilled the mounting holes. And drilled two 7/8" holes to run the wires for data and power out through the bottom into the base.

Center Support Rod:

The threaded rod was left long for now but all the bolts and washers were installed. To keep it together each bolt has a lock washer and the inside has 2 bolts for each side that are tightened into each for extra hold. Wide washers are used to help stabilize it.

Vertical Support Bars: It helped for this step to have a wooden disc/template the same diameter as the support structure, which is 18" in this case. Since the ring rollers aren't precise or consistent and its hard to tell when its the right size, its easiest to have something to compare to. Although after completing this project, it would be best to only use one instead of the two shown, as the thickness caused some issues because they intersect at the top. Which also meant they weren't the same and were slightly different to try and make up for it.

Calculated the circumference of a 18" diameter circle and cut two lengths of 1/8" x 3/4" aluminum bar.
Marked the center and drilled a hole, same size as the threaded rod.
Used some scrap bar to get the ring roller close to the right diameter, then rolled the support bar into full circles.
Checked them against the template and adjusted.
Hardest assembly part is to find where to bend the aluminum bar to flatten the bottom for mounting to the base plate and flange. Used the center hole as the top reference, the wooden disc/template, a straight edge and a measuring tape(like for sewing, since it has to bend to measure the round object precisely)
With the top center marked and already knowing the distance from the top of the support bar to the base plate, the straight edge was used to mark the bar, then measured(with the tape) from the top center hole, and adjustments made, since both marks should be an equal distance from the top center hole.
Hammered the aluminum bar flat at the marks, careful not to distort the rest of the shape.

Step 4: Part Assemblies(Cont.)

Calculated the circumference of a 18" diameter circle and cut two lengths of 1/8" x 3/4" aluminum bar.
Marked the center and drilled a hole, same size as the threaded rod.
Used some scrap bar to get the ring roller close to the right diameter, then rolled the support bar into full circles.Checked them against the template and adjusted.
Hardest assembly part is to find where to bend the aluminum bar to flatten the bottom for mounting to the base plate and flange. Used the center hole as the top reference, the wooden disc/template, a straight edge and a measuring tape(like for sewing, since it has to bend to measure the round object precisely)
With the top center marked and already knowing the distance from the top of the support bar to the base plate, the straight edge was used to mark the bar, then measured(with the tape) from the top center hole, and adjustments made, since both marks should be an equal distance from the top center hole.Hammered the aluminum bar flat at the marks, careful not to distort the rest of the shape.

Equator Support:

Rolled from 1" aluminium bar, trial and error to make it fit good inside both lateral supports.
Installed the base plate with the vertical supports and center support rod into the bottom of the acrylic shell.
Used the acrylic shell(which is exactly half the sphere) to find the exact position for the equator support. Clamped and marked both the equator support and vertical support for drilling and riveting.
Cut it to length so the ends sat flush together with the seam behind a vertical support. Each side got a pop rivet.
Left it installed til after the metal strapping was installed, so all the rivet holes could be marked then drilled.

Step 5: Finalize Support Structure

Used for the rest of the support structure was perforated metal strapping, for hanging pipes and other construction uses. The standard stuff found at hardware stores is too thin at 28 gauge, but 20 gauge was found online(eBay/Zoro.com)

The strapping was still too thin to put through the ring roller, but it unrolled fairly well so it was formed by hand, using the wooden disc/template of the right size.
It was cut to length with enough extra to bend and screw it down, and the center of it placed onto the the threaded rod.
The first one as trial and error to get it correct, by using the equator as a guide the diameter was figured out and the bottom of was bent to line up with the base plate.
Then the holes in the strapping were counted and used as a measurement to make the rest the straps the same as the first. There are 6 pieces of the strapping but if this was done again, and one of the vertical support bars were removed, there would have been 7.
The metal strapping was positioned(as best as possible) and screwed to the base plate using self tapping hex headed screws.
Lastly the metal strapping was pop riveted to the equator support.

Step 6: LED Strip Installation

The type of LED strip was chosen over other types for a few reasons. See Pixel Chipset Comparison

Pixel density, used here is 48 LEDs/Meter LPD8806. Other choices were 32 LEDs/Meter(WS2801), which was not enough. Or 60 LEDs/Meter(WS2812B) which was way too many. The rows should be the same distance apart as the pixels are on the strip, so the total amount of pixels can quickly get pretty big with the higher density strips.
Control and Data Rate, LPD8806 can accept data really quick over other options which allows higher frame rates. The control scheme is really simple, but unfortunately only has 7-bit color.
Cost and Availability, already had it in stock and its on the lower end cost wise vs the other chipsets.
Drawback is the 7-bit color and the strip is cuttable every 2 LEDs rather than every 1 like some types.

Installation:

Layout a control plan, where the first LED will be, the direction the strip will go and where the last LED is etc.(see attached image of patch for details)
Pick a direction and always run the LED strip the same direction(left to right or whatever)
Started on the equator, pulled the LED strip off the spool and cut it to length after it was applied. Didn't always make a full rotation, so there was a small gap left.
Using the same spacing as the LEDs, the next row up was applied and cut to length. Made it as straight as possible.
The middle rows are pretty flat and easy to mount as the rows went up higher and got more distorted the best method was to carefully bend/pinch the LED strip on the seams to make it sort of accordion. The change of the shape allows it to conform better to the shape of the sphere. But to much broke a few pads that had to be soldered back together.
As the LED strip was placed, the occasional zip tie was used to keep the LED strip in position since the adhesive was not going to help very much other than initial positioning. The LED strip didn't quite match up with the holes in the metal strapping, if built again a way would have to be found to make the holes match up with the LED spacing, as it would have made it a lot easier.
But at the very top top that method won't work, and LED strip rings had to be made for each row. Using single sections of LED strip and solid strand wire. Then taped to prevent shorts, but shrink tube should have been used.

Step 7: LED Strip Wiring

Wire It Up:

With the layout plan ready, start wiring. This sphere is divided into two sections, top and bottom hemispheres. This leaves the option controlling them as one string or in two strings. The top half is considered the first string, so it has JST-SM connector on its DATAOUT, that DATAOUT can be connected to the bottom hemispheres DATAIN to make it one string, or the top and bottom DATAIN can be connected separately.
First cover the aluminum bar, where all the connections will be made, with electrical tape to prevent shorts.
Used solid strand to connect in series all the +5v and GND connections on the LED strip. (White and green wire, meant to use green for all the grounds)
Then used some 2-conductor twisted wire to connect the DAT and CLKs in series(red and black wire, also should have been different colors, but that is what was available)
Last some 4-conductor ribbon cable with JST-SM connectors was soldered to the data in of both strips and the data out of the top strip. The wires were made long enough to go out the bottom of the sphere into the base where the controller and power supply will be.

Power Wires: The LED strip can't handle all the current that will run through them, which causes numerous problems(heat, voltage drop, etc) So a few direct connections to the power supply is required. This matrix is calculated to use up to 75 Amps at 5 volts, so it will need some solid power connections.

Used some solid strand to snake a +5v and GND wire to every row on the opposite side of the sphere from the data connections. Stripped the insulation back, without cutting the wire and soldered it down to the proper pads. So it is all one piece of wire with solder points along it. Not a great method as the insulation can melt/burn and cause poor solder joints if one is not careful.
Then ran 3 pairs of 16 AWG stranded wire(heavy gauge red and black wire) out the bottom, that will connect directly to the power supply.

Step 8: Base and Power Supply

The base holds the controller, power supply, wires and connection jacks.

A lamp reflector(domed sheet metal) from a halogen floor lamp was used as a lid.
3" aluminum bar was ring rolled to fit inside the lid and form the outer wall.
The ring rolled outer wall was dry fit, marked for the AC socket(with merged power switch and fuse), XLR in/out, USB jack, and a hole for the button.
Made the cut outs and holes on the outer wall. Test fit everything and made some adjustments with a file.
A 3/4" thick plywood base plate was made with blocks added to hold the outer wall in place.
With the lid on, 4 holes were drilled through the lid into the base plate.
The base plate, lid and ring rolled outer wall were all primed then painted flat black.
4x T-nuts were installed into the base plate from the bottom.
Built brackets out of metal strapping for the power supply, and secured onto the base plate.
The lid was secured to the bottom of the sphere's bottom mounting bracket using pop rivets.
Wired up all the power wires, data wires, A.C. wires.(Some connections happen on next step)
Cut 4x bolts to length to fit through the lid into the base plate. Tapered the bolt ends with a grinder then re-tapped so they would be easier to insert.

Step 9: LED Pixel Controller

Choose A Controller:

Lots of options out there, very much depends on what you want to do and how you want to do it.
With 1238 pixels that is 3714 channels of data or 8 DMX universes.
The selected controller should be compatible with the software that will be used. Commonly 8-N-1 Serial over USB or an adapter is supported. Or Art-Net based solutions.
Future NLED controllers will support video playback from an SD card for stand-alone video. In addition to expanding support to thousands of pixels.

Recommended for most pixel types and configurations is a NLED Pixel Controller Mini or Pixel Controller Micro, as they support over 1024 pixels(at least 1238x of LPD8806, higher pixel amounts may be supported at varying baud rates and frame rates) and accepts a standard 8-N-1 serial signal(over RS-485 or TTL) at baud rates up to 1Mega baud(1,000,000, 4 times faster than DMX).

For more advanced functionality and native USB control, the Pixel Controller Ion or Pixel Controller Electron could be used in conjunction with the Mass Control firmware.

The choice for this project was a Pixel Controller Ion with special firmware. It supports both RS-485(differential serial) or USB for interfacing from the software.

Arduino:

This project would be easy enough to code for an Arduino, would only need to collect the serial bytes, frame it, and send it out the SPI bus to the LPD8806.

Light Pollution:
After some power up tests and some adjustments to the patch file, it was found that since the interior is all open that there as a a lot of light pollution causing washed out colors and for the support structure to produce shadows on the acrylic sphere. This effect was expected, but not so much of it. So a solution was found to use black vinyl strips, same as vehicle and window decals, as wide as the LED spacing with holes cut out for the LEDs. Vinyl is naturally glossy, so the strips, while still on their backing paper, were sanded with 320-400 grit stand paper to make them matte. They were applied over the entire support structure. Made a huge difference in image quality.

Step 10: Software and Content

Software Options:

NLED Matrix: http://www.nledshop.com/nledmatrix/

Free, Open Source, Modifiable. Processing 3.0
Serial/TCP/UDP/WiFi communication methods.
Patch / Mapping support for odd-shaped matrices.
MOV and AVI movie file support.
Webcam/Capture capable, use third-party visualizers like Milkdrop
Not fully developed and buggy. May be revamped in the future.

Glediator(Recommended): http://www.solderlab.de/

Free and refined.
Many generated content options.
No MOV or AVI support.
Stable and easily configurable.
No native advanced pixel mapping / patching, but can be through application.

Jinx: http://www.live-leds.de/downloads/

Free and refined.
AVI movie file support.
Many generated content options.
Webcam/Capture capable
No native advanced pixel mapping / patching, but can be through application.

Both Glediator and Jinx can support Patching / Mapping for odd-shaped matrices via another software application NLED Live Patcher.

MADRIX could also be used with the proper controller.

Used here and developed for projects such as this is NLED Matrix, it is free, open source, and versatile. It supports single color, RGB, and RGBW(in the future) LED matrices. With a simple(and customizable) control protocol, that can interface with serial(COM ports) UDP, and TCP communication.

Since the LEDs are laid out in a non-rectangular arrangement, the software has to be told what order/position the LEDs are arranged in so it can send out the data in the correct order. This is called pixel patching or mapping, and not many software applications support it. A project like this can not be controlled without pixel mapping / patching. The NLED Matrix Patcher software can be used to create custom and unique coordinate files that are used to pixel patch or pixel map. NLED Matrix supports the coordinate patch file, and other third-party software, such as Glediator, can support pixel patching/mapping using the software application NLED Live Patcher. NLED Live Patcher intercepts a virtual serial port(via com0com or similar) and using the coordinate patch file, it reorganizes the data and sends it out to a physical port.

NLED Matrix Patcher(Free and Open Source) - Used to create coordinate patch/map files of any size, shape, and non-contiguous matrices.

NLED Live Patcher(Free and Open Source) - Intercepts serial data streams using virtual serial ports and applies a patch/map coordinate file and retransmits to the physical serial port(USB or otherwise). Plan to add TCP/UDP and Art-Net to compatibility to future releases.

Content: Odd shapes and low resolutions(this is 68x24) makes it difficult to use most videos and footage. The process of shrinking a video source down causes the end result to be washed out with no detail or contrast. Most of the content would have to be made specifically for the sphere. The software applications can create generated content such as text, falling blocks, color effects, and similar. The feeds they create are scaled to the matrix size and are usually a good choice for content.

Otherwise videos could be made in Adobe After Effects or similar software that can create graphic effects. The created video should match the matrix size(example, 68x24 pixels in size)

Step 11: Usage and Final Thoughts

Find updates and more information on the project's webpage at http://www.nledshop.com/projects/spherematrix/

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