Build a pixel tree

If you haven’t figured it out yet, all the articles in this issue of PlanetChristmas Magazine have been leading us to building our own pixel based megatree. We’ll readily admit it’s not as easy as it needs to be, but the results are so worth it. Just look at the cover of our magazine and imagine the light patterns in a fluid movement.

Our goal is to build a tree that’s two meters tall (a little over six feet), have 12 vertical legs and each leg will use 60 pixels/meter pixel ribbons. With the help of a calculator we figured out that’s 120 pixels per leg. Since each pixel requires three control channels it means 360 control channels per leg. To keep things as simple as possible, we’re dedicating one DMX-512 universe to each leg meaning we’re using only 360 of the available 512 channels.
Taking one more pass at the calculator, with each of the 12 legs using 360 control channels it works out to a total of 4,320 channels. That’s quite a few more than a typical 16 or 32 channel megatree.

Why make a pixel based megatree? Since any light can be any color at any time, our tree will have swirling designs, scrolling text, fireworks and just about any other image you can imagine. One word is the result: WOW.

Here’s our parts list:

• 12 pieces of 10’ EMT (Electrical Metallic Tubing) ½” conduit
• 6 pixel ribbons. Each 4 meters in length, 60 pixels/meter. 5 VDC. We used WS2812B based pixels: part number HC-F5V-60L-60LED-B.
• 75’ 3 conductor, 18 gauge wire
• 100’ 2 conductor, 18 gauge wire
• 1 Joshua One ECG-P12S E1.31 to SPI gateway controller
• 2 Meanwell SE-350-5 5VDC 300 watt power supplies
• 1 Dri-Box 330 Outdoor Waterproof/Weatherproof Box
• ¾” black heatshrink tubing or black paint
• Miscellaneous zip ties, heatshrink tubing, etc.

Tools needed

• Pipe cutter
• Soldering iron
• Wire stripper
• Magnifying glass
• Drill with ¼” bit for metal work
• Heat gun or torch for heatshrink tubing

Construction

We cut each of our 4 meter pixel ribbons in half. The best we can tell, the ribbons are manufactured one meter at a time and soldered together to make the final length. We simply cut the ribbon at the middle solder joint of the 4 meter ribbon. We tinned the metal fingers at both ends of the pixel ribbon with our soldering iron.

Electrical conduit comes in 10 foot lengths. We want to use them as a rigid backing for our way-too-flexible pixel ribbons. The good news is these are easy to store in the corner during the off-season.

We cut each conduit down to 84” (7 feet) in length. The two meter pixel ribbon is almost 79” long but we wanted a little extra conduit at each end for mounting purposes.

There was quite a bit of discussion about painting the conduit black so it would not reflect other lights that might be in the display. We tried fancy spray paint but it chipped off too easily if we banged it against anything (like another piece of conduit.) Someone suggested powder coating (in essence baking the paint onto the conduit) but that was going to cost $10 USD per piece of conduit. We ended up using black ¾” heatshrink tubing to cover the entire length of each piece of conduit (see below, left). Now each piece of conduit absorbed the errant light well and added a bit of cushion to the outside. Making the conduit a dark color isn’t an absolute requirement but it does make a difference at night.

2.5” in from each end of the conduit we drilled a ¼” hole. This was used to run power injection. The power and pixel data signal enter one end of pixel ribbon on the conduit. We ran a 2 conductor wire inside the conduit, threading it in and out of the ¼” holes and made sure power was also applied to the pixel ribbon at the opposite end. This is a best practice to make sure your pixel ribbon doesn’t go dim at one end because of lack of power. Look for other articles in this magazine about power injection considerations.

We found the center of the conduit (42” from either end) and made a temporary mark on the pipe. We then found the center of the pixel ribbon (typically, look for the solder joint in the middle or you can count the total pixels, divide by two and count that many from one end) and made another temporary mark on the ribbon. Most pixel ribbons have the clear silicon sleeve running the entire length to make them weatherproof. We used some pieces of double-faced tape about every two feet and gently attached the ribbon to the conduit starting at the center of the conduit and working out. The double-faced tape will hold the ribbon to the conduit long enough until you can attach some zip ties (tie wraps) at regular intervals. The trick is to get the pixel ribbon down the center of the conduit. It tends to want to drift into a slight spiral. We found putting your eye at one end of the conduit and looking down the entire length helps make sure your ribbon ends up being straight.

Time to break out the soldering iron and solder the data/power cable to the DI (Data Input) end of the pixel cable. We make our cables six-eight feet long as a best practice. Longer data cables can lead to data timing issues and the pixel ribbon can start acting very strange. Don’t forget to solder in the power injection cable at both ends of the ribbon. Take your time and make sure + goes to +, etc. We used some waterproof connectors but if we had to do it over again, we wouldn’t use them.

Make double darn sure you follow the data arrows on your pixel ribbon. Your data cable must enter at a DI or data input end of the pixel ribbon. See other articles in this magazine for DI and DO.

We used clear or black heatshrink tubing over where are solder connections were to stabilize the joints and keep the weather out. The first piece of conduit is the toughest as you develop your technique.

Repeat the above until all your pixel ribbons are mounted to the pieces of conduit. The worst is done.

Build the Controller Enclosure

The nature of these pixel ribbons is they need their controller pretty close to them. That means the power

supply(s) and controller electronics will probably end up outside. Just about any outdoor enclosure will work but we ended up using the Dri-Box 330 Outdoor Waterproof/Weatherproof Box. It provides plenty of room and uses some sort of magical gel where the wires penetrate the box to make for a weatherproof seal. We used two low voltage power supplies and each was wired to a different half of the controller board.

Look closely at our build above and you’ll see a couple of vampire plugs. We added these because there was already high voltage entering the enclosure for the power supplies and we figured in the future we might add something else inside the spacious box.

Connecting the pixel ribbons

For this particular build we used a Joshua One ECG-P12S E1.31 to SPI gateway. We’ve also used the Advatek Lighting PixelLite and SanDisk E682 controller boards. They all do basically the same thing, though each board setup is different.

Be very careful connecting the cables from your pixel ribbons to the connectors on the controller board. We used a permanent marker to label the pinout of each connector on the controller board. These are typically four pin connectors (positive voltage, data, clock and ground). We are using WS281x based ribbons so we only connect to the positive, data and ground pins. The good news is all these controller boards are versatile and can be configured for almost any type of pixel device.

Configuring these controllers can be intimidating at first so you might have to spend some time learning your way around. Here’s our final configuration screen for the Joshua One ECG-P12S controller with all the pixel strings attached. This setup worked very well for us.

Testing

Some of the controller boards have a built in test function. Now’s a good time to use it. All the pixels on all the ribbons are exercised and you’ll quickly pinpoint any wiring issues. For this build we are using the WS2812B type pixe

ls and discovered they’re close to dummy-proof. Accidently wiring the voltage backwards on a pixel ribbon did no permanent damage. We weren’t so lucky with some of the other pixel devices.

Time to Dazzle

We got a very early version of the Light-O-Rama sequencing package taking advantage of their xLights/Nutcracker addition. For our testing we simply defined the E1.31 configuration in xLights/Nutcracker, created a model of 12 strings of 120 pixels and started randomly playing with features in the Preview tab. See the pictures on the next page. Get ready to be impressed.

Conclusions

With a little bit of effort we created a two meter tall pixel tree where each of the 12 legs had 120 pixels. Any light, any color at any time. The results were, well, beyond our expectations. We ended up building several different pixel trees ranging from less than one meter high to a full five meters high using different pixel density ribbons. Pixels are here. Use them in your display and dazzle your audiences.

We’ll be looking deeper into pixel sequencing in a future PlanetChristmas Magazine. While waiting, build those pixel trees!

This article was included in the April 2014 issue of PlanetChristmas Magazine.

By Scott Farcus