It's all about the blinking...
This year I decided to embark on making a totally unique item from scratch. After seeing Colin's single color LED ball, I decided to modify the design and create RGB versions. To help others to understand how they work, I have created this page to show more detailed images and descriptions.
A quick demo of what the balls look like is in order. This shows 6 of the RGB LED balls, and 15 pixels kindly donated by Ray Wu and driven by the Stellascapes E16 (which will eventually drive 800 pixels). Excuse the video as it was shot with the iPhone 4, so colors are not ideal :)
Step 1: After lining the mold with a non-stick wax and then a release agent, the outer white coat is added to the mold and left for 12 to 24 hours before the next step. This white color gives a more even white color, as well as providing a much better quality coat.
Step 2: After the outer coat has had time to dry the main body of the fibreglass is added. 2 layers of glass mat and about 25ml of resin is used in each half, and once completed it is left for another 12 to 24 hours before being removed from the mold. An "X" pattern is cut from the corners into the center of the glass mat to allow it to more easily fit onto the curved surface, and the layers are offset by 1/8th of a turn. Because of the overlapping caused by the curved surface, parts of the ball have up to 4 layers of glass, and the sections which have just 2 (at the base of the mold) there is a heavier coating of resin. The blue color seen on the mold is the release agent.
Step 3: After the balls are dry, they are removed from the mold. Initially there is a reasonable amount of excess at the end of the half, and this is roughly cut off. I have saved these offcuts of clean glass and they are used to replace one layer of glass in every 5 or 6 halves, rather than throwing it out. The blue color is the remains of the release agent. Sometimes there are defects caused by the tape, used to cover the join between the mold halves, lifting slightly. When the next mold is filled with white top coat a layer is added to the defects from the previous halves and once it is dry they are lightly sanded to remove the defects.
Step 4: Once and defect fill has dried the edge is trimmed neatly using a dremil and cutting disc, and the surface is given a very light sand to allow a coat of paint to stick to it. Once it is painted and left to dry, it is again given a very light sand and you end up with an undrilled half as shown below.
Step 5: A series of marks is lightly pencilled around the half and where these cross a 5mm hole is drilled through the fibreglass.
Step 6: Once the holes are drilled the ball is now ready to be made a little nicer on the eye. Rather than having a plain white, most baubles on a christmas tree are covered in shiny or colored paint. I had some color flecks left over from a kids project, so a layer of clear topcote gel is added to the ball and then it is sprinkled with some color flecks (some green, some red and some gold). Once this dries a second coat of gel coat is added to stop the flecks coming off as it is handled when inserting the LED's. Once the 2 layers of gel coat have dried the LED holes are re-drilled to remove any gel coat which has collected in them.
Step 7: Now the LED's have to be built. Each LED has 3 resistors soldered to it, and 84 are required for each ball. This small holder was created to make soldering the LED's easier. 100 ohm resistors are used on the green and blue LED sections, and 180 ohm onthe red due to it's lower internal voltage drop. Eash LED draws 20mA per color, so that is 1.68A per color. In reality it is closer to 1.2A per color and 3.4A when they are all on, giving a white light.
Step 8: Now comes the hard part - putting all the LED's into the ball halves. This takes time and patience, and the end result is shown below. Once the LED's are in place they are tested for a minimum of 2 hours to ensure they are OK, and then they are secured in place with a light coat of resin over the inside of the ball. This Stops the LED's from coming out, as well as partly insulates the wires inside to stop them shorting out if the ball is dropped. Small slivers of fibreglass are draped over the wires to further provide mechanical protection and support (not shown)
Step 9: The last step is to fill the half with self-expanding foam to give permanent mechanical protection, and then mount the 2 halves together and seal the join. Once the join is solid, a small sprinkle of the glitter along the join line gives a seamless look. During the filling and joining process the ball is illuminated to ensure nothing is shorted or damaged in the process. I know the joins can be seen in the images, but I am getting better are hiding them, and they are almost invisible through the day at 15 meters (Viewing distance) and totally invisible at night.
Once the join is completed and dried, a final clear coat is placed over the entire ball to seal around the LED's and power cable as well as give the ball a really glossy final coat to make it look great from both up close and from a distance.