Here's how we constructed a wooden Christmas tree decoration with colour-changing LED lights.
Step 1: Required Parts and Tools
You will need the following parts:
- 1 piece of MDF (whatever size you want your tree - ours was about 70cm x 50cm)
- Red, green and brown paint
- Hot glue sticks (lots of them)
- Slow flash colour-changing RGB 5mm LEDs
- - we used 31 for our size of tree
- - we got ours from ebay.co.uk trader "amigoofchina"
- One or two white LEDs
- - ours also obtained from ebay:amigoofchina
- One resistor for each LED, suitable for your chosen supply voltage (our LEDs came with free resistors for use with 12v)
- One 12v _regulated_ mains adapter
- - also from Ebay
- - rated at 1000 milliamps (the tree uses about 600ma, so we're not running it at maximum)
- - we chose a switched-mode adapter, because they don't get so hot, the voltage regulation is good, and it's protected against overload and short-circuit
- One inline power connector (suitable to attach to whatever connector is on your power adapter)
- One inline fuse holder (for 20mm fuse)
- One 20mm fuse (we used a 1 amp fuse, but it depends how many LEDs you're using - they consume ~20 milliamps each)
- Some flexible insulated wire
- Some solid copper wire
- - we stripped some 3-core mains wire to obtain ours
- Maybe some insulation tubing, or insulating tape
- Some thin card and masking tape
- 5mm wood drill bit
- soldering iron and solder
- a couple of screwdrivers
- hot glue gun
Step 2: Draw the Tree Outline on the MDF
Draw a Christmas tree shape onto the MDF, including the trunk and a pot for it to stand in.
You'll need the main part of the tree to be fairly solid so don't be tempted to extend branches out from the trunk - you just want the outline shape.
Step 3: Cut Out the Tree Outline
Now use your saw to cut out the tree outline. Try not to cut off your fingers as this will make the later steps more tricky.
Remember to wear a face-mask while cutting MDF or you'll be coughing and wheezing all through the holiday season.
When you've finished cutting, use a piece of sandpaper to sand any rough edges smooth.
Step 4: Mark the Positions for the LED Holes
Next you need to mark the positions for the LED holes. We used 31 "paper holes" collected from the inside of a paper-punch to first decide the positions, and then when we were happy with the layout, drew round them with a pencil.
We imagined that the lights were connected on one long string of wire, like real Christmas tree lights, rather than try to distribute them evenly in all directions, but you can do it however you want to.
Step 5: Drill the Holes
Here you can see my assistant drilling the holes. Note how he is holding the wood firmly to the bench, with his hand well away from the power-drill. We don't want any red colour where we want green.
Note also that he's taking care not to drill a hole in Daddy's bench.
It's best to drill from the side that you want to be the front (if it matters which side is which), because the drill tends to snap out of the back and make a less tidy hole on the other side.
Depending how thick your MDF is, you may find it drills easier if you keep lifting the drill out as you drill, to clear the MDF "dust" from the drill bit.
Step 6: Draw on a Star Shape
Next, draw on a "star" shape at the top. This needs to be a bit bigger than the holes for the colour-changing LEDs.
Step 7: Drill and Cut Out the Star
Drill a couple of holes inside the star shape, then use a small saw to cut out the rest of the shape. This is easiest if you have a jig-saw.
Step 8: Paint Your Tree
Now paint your tree.
The green paint we used for this one was a bit thin - almost ink-like. For an earlier one we made we used a thicker paint, which was better because the brush-strokes made it look more tree-like.
Don't forget to paint the edges as well.
Step 9: Prepare the LEDs and Resistors
First, identify the anode and cathode on your LEDs. They have to be connected to the power supply the right way round or at best they won't work, and at worst they'll break.
Decide whether you're going to connect the resistors to the anode or cathode and stick to it, so you can identify the leads after you've bent the wires.
We decided to connect the resistors to the anode (the longer wire on our LEDs), so the resistors will be connected to +12v.
Pop a LED into a hole. Put the blade of a screwdriver at the base of the wire that won't have the resistor attached to it (near the plastic LED housing), and use another screwdriver to bend the wire over the first screwdriver blade. The idea is to get the bend in the wire a short distance away from the plastic housing of the LED, so it's less likely to snap off in the process.
Now wind one side of the resistor tightly around the other LED wire.
Do the screwdriver thing again with the wire on the resistor side of the LED, with the aim of getting the first LED wire and the other side of the resistor pointing in opposite directions.
Finally, snip off any excess wire after the coil of resistor wire.
Repeat for the other 30 LEDs, and the white LED(s) for the star.
Step 10: Insert the LEDs and Wire Them Up
Put a LED into each hole, with all the resistors facing in the same direction.
Now you need to connect all the resistor sides together using solid copper wire, and all the non-resistor sides using more solid copper wire, and none of these wires must cross over.
If you run a positive wire up one side of the tree, and a negative wire up the other side, then you can branch off and cross for each row of LEDs.
At the bottom of the tree, the fuse needs to be wired into one side of the circuit (it doesn't matter which side). Keep the fuse quite close to the power connector, as it won't protect the wire on the connector side of the fuse.
If the positive and negative wires must cross over somewhere, use some insulating tube or tape to keep them from touching. It's important to do this carefully to avoid any chance of causing a short-circuit that could at worst start a fire.
Twist the resistor/LED wires around the copper wire and solder together. Solder the resistor to LED connection too.
Use one or more white LEDs for the star at the top. Obviously you haven't got a nice round hole to keep these LEDs in place, so bend the various wires to keep the LEDs roughly in the right place.
If you have trouble keeping the LEDs in place while the wires are connected up, you could glue them in place first, but take care not to get glue where you'll later need to solder. A bit of glue squirted into each hole from the front side would probably hold them in place, if you can manage to hold each LED while the glue sets (take care - it's hot!).
Step 11: Glue Everything in Place on the Back
Once all the wiring is done, get out your hot glue gun and glue everything into place.
In the second picture here you can also see the fuse and fuse holder, and the inline power socket wired in.
Step 12: Glue the Front
Flip the tree over, and start filling the LED holes with glue, so that you end up with a little mound of glue poking out of each hole.
The glue sets slightly opaque, which helps the light to appear more even from a wider range of angles. The LEDs by themselves send out light in a fairly tight 20 degree cone, which you would only see properly if standing right in front of the tree.
Initially we tried embedding some tiny glass beads in the glue to create a sort of "sparkling" look, which sort of worked, but also made the lights too dim. So we dug them out and re-glued the holes.
Step 13: Insulate the Back
Unless you use a _lot_ of glue, there will be some bare copper wires on the back, which could short out if they touch something conductive.
To avoid this risk, we cut out some thin white card and stuck it to the back.
Step 14: Plug in and Switch On
Check one last time that you've wired everything up correctly. Follow the positive wire from the socket to the positive side of each LED, making sure it doesn't touch the negative side, and vice-versa.
If all is correct, plug in and switch on. Put on some Christmasy music (preferably with sleigh bells), get a glass of mulled wine, sit yourself in front of the tree, and loose yourself in the hypnotic colour-changing lights for a while.
Then snap out of it and tidy up all that mess you've made while making the tree.