Pixel Megatree

January 15, 2015
The 48 LED string megatree has served us well the last 3 years, but it is time for an update.

I have been very happy with how the Pixabulbs that I put on the eaves and roofline have performed. I had no failures, and they have been out for several months in rain and snow. So I am looking to use those for the megatree upgrade. The next decision is how many strings to use and what bulb spacing to use.

In the DIY LED Express January pre-sale, you can order Pixabulbs with custom spacing in 2″ increments. Once the pre-sale is over, you can only get them with 6″ spacing. My initial thought is to get them with 6″ spacing. That way, if I don’t get enough strings in the pre-sale to get the look that I want, I can order more later.

With that decided, now I need to think about how long of strings to use. The out-of-the-box choices are 25 and 50 bulb strings. I can do strings of a different length, but that means soldering. When I did the eaves and roofline last year, I ended up doing a ton of soldering that took forever, and I don’t want another year of that. So I will go with one of the pre-built lengths. A 25-bulb string is 14.1 feet from the first bulb to the last bulb. The LED strings on my current megatree are 16.5 feet long, and I don’t want the new tree to be smaller than the existing one. So it looks like I will be going with 50-bulb strings. A 50-bulb string is about 28′ from the first bulb to the last bulb, so the new tree is going to be nearly twice as tall as the existing one.

With that decision made, next I need to decide how many strings to get. A general rule of thumb is that you want the horizontal spacing between bulbs and the vertical spacing between bulbs to be the same somewhere around midway up the tree. Time to break out the trig calculations.

I like the shape of my existing tree and want to keep the new one as close to that as I can. Since the new tree will be considerably taller than my existing tree, I need to increase the diameter of the base ring as much as possible. The dimensions of the circle drive will limit how large I can make this, so I’ll make it as large as I can.

Using 48 strings and a base ring that is 16′ in diameter, the spacing between strings will be about 6 1/4″ midway up the tree. Pixabulbs with 6″ spacing are actually about 6 3/4″ inches from bulb to bulb. This means the equal spacing point will be just below halfway up the tree, which should be fine.

I use SanDevices controllers for all the pixels in my display, and I am going to continue with that direction. To drive 48 strings, I am going to use three E682 controllers, each with a 360W 12V power supply. This is certainly not the most economical solution. I could drive all of these new Pixabulbs with a single E682 controller, but I would have to have longer strings, I would have to inject power, and I would still need 3 power supplies. In order to keep the layout as simple as possible, I’m going with the separate controllers and power supplies. This way I will have just one string of 50 bulbs on each output.

Now to think about the center pole. I was very happy with the center pole system that I built for the existing megatree 3 years ago, so I want to do a very similar concept to that one. The only real flaw in the current one is that it is much heavier than I wanted. It is made out of 2″ square steel tubing that is 1/4″ thick. I will stick with the square tubing, but the walls can be considerably thinner than 1/4″. This should help with getting the center pole put up and taken down. I will use a similar guy-wire system to what I use today, hopefully I can use the same connection points that I use on the current tree.

I will also reuse the movable hook head and winch concept from the existing tree. These have worked perfectly in the past, so there is no reason to change them.

Another thing I need to think about is how to mount the Pixabulbs. They have to be attached to something that will bear their weight, they can’t just hang from the top. There is a member on DIYC that makes plastic strips that can be used to attach the bulbs to. With these strips, you pop the lens of a bulb, them put the lens back on with the strip in between the lens and the base of the bulb. I don’t especially like this method. When I accidentally knocked the lens of one of my roofline Pixabulbs, I had trouble getting it to stay after I put it back on. I ended up hot-gluing it to the base to get it to stay on. I have not heard of anybody having this problem, but it still worries me. The other thing about the strips is that it blocks most of the lights on the back side of the tree. I’m not planning to do effects like text or images where this blocking is desired.

I am thinking about using 1/2″ wide metal banding, the kind they use to strap things to pallets for shipping. It is the same width as the string wiring, so it won’t block any additional light from the back side strings. It is also plenty strong to support the weight of the string, and it should not strech over time.

January 19, 2015
The DIYC member that makes plastic strips has come up with a new version that lets you mount Pixabulbs without having to take the lens off. This sounds very promising, there should be some details on these new strips available later this week. I think this would be a better solution than the metal banding. The wider strip will help block some of the light from the backside of the tree from the viewer. I won’t have to use a bazillion velcro ties to attach the lights to the strips. The only problem is that these strips will probably come in 8′ lengths, so I will have to have multiple strips for each string of lights.

August 18, 2015
Well, I’ve been busy since January on other projects, but now I’m ready to get back to lights for a while.

The new Pixabulb mounting strips were available a while back, so I bought enough of those to do the entire megatree. These will make life much easier mounting the lights.

There is also a brand new controller out from the guys at FalconChristmas called the F16V2. It has 32 ports on the controller. I liked the idea of using a single controller for the entire megatree instead of multiple E682s, I figure I am less likely to have timing issues that way. So I ordered it and it is now here.

So it’s time to start getting all the controller-related stuff updated for this year. In past years, I used some plywood present boxes to cover all the controllers, and the controllers just laid on top of the mulch in the circle drive. This year I am going to improve on that. I am taking the largest present box and mounting everything to the walls of that. What was the top of the box will become the bottom, and I will build and paint a new removable top. This will allow me easy access to everything. There will be a good sized hole in one of the bottom corners so that the box will fit over the top of the power stake in the center of the circle drive. There will also be smaller holes in the bottom to run all of the controller cabling out to the megatree.

Since the controllers will be in a reasonably weatherproof environment, I am still going to mount everything in CG-1500 boxes, but I am going to leave the lids off.

First step is to mount the power supplies. The F16V2 will support a total of four power supplies, and I will need all 4 to drive the megatree. So I am going to mount 2 power supplies each in 2 CG-1500 cases. First I need to grind down all the standoffs that I don’t need. I use the Dremel with a cut-off wheel for that.

Then with my paper template, I marked and drilled the mounting holes for the power supplies.

Then I installed the power supplies. I used M4 x 10mm bolts, just like past setups.

I didn’t like how my power cable strain-relief clamps mounted last year. So this time I am just drilling 2 new holes in the bottom of the case to install those. I will use the existing holes to run the DC power out of the case.

Then I installed the input power strain-relief clamps.

I also drilled 2 holes at the top of the case and 1 at the bottom of the case that will be used to bolt it to the side of the present box.

Now, on to mounting the F16V2 and the daughter card. Each of these will go in their own CG-1500 case, again without lids. First I will mount the F16V2.

I needed some additional standoffs so that the bottom of the controller doesn’t rub on the case standoffs. For that I used 3/8″ sections of 1/4″ refrigerator water tubing.

I marked the standoffs in the case where they need to go and hot glued them in place.

Then I used six #6 x 3/4″ sheet metal screws to mount the controller in the case.

I drilled 2 holes at the top of the case and 1 at the bottom of the case that will be used to bolt it to the side of the present box.

I drilled four 1/2″ holes at the bottom of these case for controller pigtails to come out. I am using these instead of the existing holes in the case because the strain relief clamps will be more secure.

Then I installed the four strain-relief clamps.

Then I installed and numbered all the pigtails that the megatree strings will attach to.

I repeated the mounting steps for the F16V2 expansion card.

The ribbon cable that came with the expansion card wasn’t long enough to reach between the 2 cards the way I will have them mounted. I bought this ribbon cable and shortened it to fit.
Ebay Ribbon Cable

Now I was ready to start mounting things in the present box. The first thing to mount was 2 power strips to plug everything into. These will go in the end of the box where the power stake will come up through the bottom.

Next I mounted the power supply cases and connected input power cords. These went on the long side of the box closest to the power strips. I shortened the power cords so I didn’t have a bunch of extra cord to deal with in the box.

Next I mounted the F16V2 and Expansion card cases. These went on the opposite side of the box from the power supplies.

Then I connected DC power wires from the 4 power supplies to the power inputs on the F16V2 and the Expansion card.

My E6804 case that runs the 8 arches in the middle of the circle drive also needs to be in this box. The network switch was mounted in the lid, but that wouldn’t leave much room to access things with the lid on, so I needed to relocate the switch. I removed it from the E6804 case. Then I removed the lid from the E6804 case and mounted it in the end of the box opposite from the power strips. I also shortened the power cord on it to just reach the power strip.

I had room for 1 more CG1500 case next to the power strips, so I mounted a new 8-port switch in another case on a piece of Lexan. I ran the power cable and plugged it into one of the power strips.

That’s everything that lives in this box. Here is an overhead picture with everything mounted.

Now to make a removable top. I laid the box upside down on a piece of plywood that would become the top. I used a 1×2 and a cardboard spacer strip against each side of the box and marked the outline. I cut the box lid out and then screwed the 1x2s around the perimeter. I painted the lid to match the box and applied 2 coats of clear UV-resistant sealer. I also lined the rim of the box with 1″ wide weatherstrip. This should pretty much keep out any moisture. I may need to put a latch on each side to keep the lid from coming off in the wind, we will have to see.

Other than cutting holes for all the cables, this part is done. I won’t cut those holes until I can get it out in the circle drive and verify that everything else is good.