In this project i will show how i made my Christmas decoration this year, a 120x80cm Christmas tree with flashing ornaments and guirlande, and the best part - absolutely no programming!
The project is a bit time consuming, as anything involving almost 1500 LEDs is, but very easy as long as you do everything right. I am not experienced in electronics in any way, and i made it through first try. I had some failures along the way, but I'll make sure to list them here, so you can skip those.
There's videos in the pictures.
Step 1: Materials and Tools
Very few tool and materials are actually needed to make this tree, and it can be done for very cheap.
- 5mm LEDs. I used almost 1100 green, 300 yellow and 100 blue
- MDF Fiberboard
- Electrical wire, about 30 meters, preferably thin wire. I stripped a telephone cable i had lying around
- An old computer charger, as many amps as possible. Mine was 18,5 volts and just under 4 amps.
The big trick here is to find flashing LEDs. On ebay there's loads of people selling these. All my green LEDs are constantly on, but the yellow and blue are flashing. I made the assumption that they would not flash in the exact same interval, causing a random pattern after a while, and i was right. In the beginning they flash all together, but after 10-15 seconds it's all random. If you do it this way, there will be no programming, no resistors, no capacitors, nothing but series of LEDs in a fiberboard.
- 5mm drill
- Soldering iron
- Scrap piece of wood
- Masking tape
- Wire stripper (this will be your new best friend, and no worries, it's cheap)
Step 2: Preparing the Design
Preparation took about half the time for this project, and it was worth it.
First draw an image, using only the colors you can find LEDs in. Word of caution, be careful with red! I ordered 100 red flashing, but i found out that when put in series they will turn off the entire series when off. Put 9 in a series, and it will almost never light up. Blue and yellow didn't have that problem, that's why i have no red ornaments on my tree.
I drew the image in photoshop, but it doesn't nearly have to be that complicated. I have some programs at hand through my school that made it a little easier, for example SolidWorks, which i used to map the pattern. This was way overkill though, i could have just printed the image, traced lines over it and scaled up on the MDF board.
The original idea was to use a chickenwire net (volier net) with square masks. Then i'd put all the minus legs on one net, and all the plus legs on another offset net, and put power on the entire net. That's the reason my pattern isn't squares, but rectangles. I ended up with another solution though, since it would require a lot of resistors to lower the voltage and draw so much current.
I found out that if i put the LEDs in series, i could eliminate the need for resistors completely. In the datasheet for the LEDs it says that they can handle up to about 2,5 volts, so since 18,5/7=2,6, 7 in a series sounded like a good idea. It wasn't...
I used my pattern to place dots on a squared piece of paper. Make sure you get the different colors mapped. Then by hand i connected every dot in a series of 7. This was very tedious, but also kinda fun, almost like solving a puzzle. I had to remind myself that a few times, when i found out that 18,5 volts will pop the series of 7 LEDs. I needed 9 in a series before it was able to handle the voltage, so i had to redraw everything. Piece of advise, test your LEDs before drawing the series. Start high, with a series of 10-12 LEDs, and take one off at a time, until it looks good. That would have saved me hours of work.
Give every series a number, and get ready for seemingly endless soldering.
To prepare the charger, simply snip off the charging plug, and strip the wires down a little.
Step 3: Soldering Jig
To make life easier, i made a small soldering jig. Using the same dimensions as i intended for the final assembly, i made a small board with 5mm holes evenly spaced. There's not really any magic to this, just measure out where to drill and put some holes in the wood. I put numbers on the rows and columns, so i could find the right ones faster.
Step 4: Make the Individual Series
Now with your handy soldering jig, start from the beginning and put the LEDs for series 1 in. Some of the legs had to be cut a little, otherwise they'll short out. Then bend the legs down, and solder them together plus to minus EVERY TIME. I put a little piece of masking tape with the number of the series on the last plus leg, and nothing on the minus. Test the connecting with the charger you're going to use, and if it all lights up, move on to number 2 and repeat. Then do number 3, 4, 5, ...., 150 (in my case). It is very very tedious and time consuming, but the soldering jig really helps. Always test the connection after soldering!
Step 5: Prepare the Fiberboard
The mdf fiberboard i used was bought so the dimensions fit somewhat, so i didn't have to cut it.
Trace the lines over the board, using a long ruler or something else straight, and make sure the spacing is the same as in the soldering jig. Be pretty careful with the lines, having them at an angle or wrong spacing can actually break the LEDs.
Then using the piece of squared paper with the pattern on it, map out the entire boundary with small circles. You don't have to draw circles in the middle, this is just to see where to drill holes and where not to.
God I wish i had a CNC router for this step... I drilled every hole with a handheld drill, using up almost 3 batteries. First i drilled pilot holes with a dremel and a 1mm drill bit, to speed up drilling with the 5mm drill a little. 1500 pilotholes, 1500 5mm holes and 7 hours later, my arm was dead and the fiberboard perforated. I sanded the surface a little to remove the ugly parts.
Step 6: Place the LEDs in the Board
This is actually pretty straight forward, again referring to the squared piece of paper, place the correct number of series in the fiberboard. If you drilled with a 5mm drill, the LEDs should stay put without needing any glue or tape. Put them on the ugly side of the fiberboard with all the lines, so it doesn't show in the end.
Be really careful placing them in the holes! If the holes are too far apart, it is very easy to actually split the LED and break it. Sometimes it's necessary to resolder the legs, so the spacing fits. It'll give a little "tick" when the tension is released.
Don't remove the masking tape yet! It will come in handy in the next step.
Step 7: Make Positive and Negative Busses
Strip a 150cm piece of electrical wire (normal 230V wire for lamps and such), and give it a good twist so it doesn't unravel. Then tape it down top and bottom on either side of the board. Presolder little pieces of both wires, everywhere there is a vertical line (about 60 places on both in my case)
Step 8: Wire the LEDs
Decide which stripped wire is the plus and which is the minus. Doesn't matter which is which, as long as you do the same every time.
Start with the bottom row, and solder the thin telephone wire to the bus. Then run it over the first vertical line, until you reach a flag. At this point you can either cut the wire, solder it to the leg, solder a new wire on and continue to the next flag, or do what I ended up doing: with the wire stripper, don't cut the wire just strip it in the middle. Then bend the stripped wire around the leg, solder it and continue to the next flag. It doesn't have to be NASA grade soldering, it's just a Christmas tree.
When you're done with the plus wire, do the same for the minus wire, and move on the next row. Repeat until you reach the top and that's it! I suggest you test the connections every once in a while, by simply connecting the charger to the two main wires. When everything is lighting up, solder the charger to the main wires, and you're done! If you're want, you can add an on/off switch on the charger, but for now, mine is just on when plugged in the wall.
If you have room to spare, it would be a good idea to add a frame to the board, so it doesn't bed so easily.
Remember this project is most definitely not limited to christmas trees. Any image can be turned into massive LED arrays this way, it's just at matter of getting the idea. I would advice a bit of caution with text though, my tree ended up mirrored, so you have to consider this before making the series.
If you have any questions, feel free to ask, that's why I'm uploading this. I have this ible entered in the Glow contest, a vote would be very much appreciated.