Here's a little video from this year's Halloween showing what it looks like in person.
Step 1: Items You'll Need
Black pants and hoodie
5 meters of strip LED lights in your choice of color(s). The length will ultimately depend on the size of the person wearing the costume but 5 meters is more than enough for a child.
Electrical tape (black is typical but I had both black and clear and used both)
9V battery connector and battery OR 3 Cell LiPo battery and appropriate connector (LiPo is MUCH brighter but is potentially dangerous and should only be used if you research the proper use of them. See HERE for battery care.)
JST connectors for connecting the pants LEDs to the hoodie
16-20 awg black and red wire. The gauge isn’t really all that important as long as it is flexible. If you have an old computer you don't use anymore, you can take the power supply and raid it for wires.
Optional but very helpful:
Helping hands for soldering
Step 2: LED Prep Work
First off, you’ll want to take notice of a few things. The LED’s come in groups of 3 lights per section. Each section is capped on the end by a set of copper contacts. When you get a new roll of LED’s, the contacts will be in between each set of 3 LED’s. If you need to cut the LED’s to length, ideally, you’ll cut in between the set of contacts so you can solder wire to the contacts to get power to the LED’s. The pictures show where you want to cut and solder.
Now that you know the LED’s are in sets of 3, you’ll want to measure out how long each strip will be for the various parts of the costume. You’ll need a strip for each arm, each leg, a “spine” that goes down the front of the hoodie, and a head that will go around the outside of the front edge of the hood. Do the best you can to cut the strips to length in between the contacts mentioned above.
Once you have everything cut to the proper length, you’ll want to do what I consider the most important part. You want to cover all the contacts that will not have wires soldered to them. The reason for this is that all of the contacts are exposed and in the off chance that you brush up against something metal or happened to touch the contacts with your ring or something else, you could short the battery out. If you use a 9V battery, it’s not as dangerous as using a 11.1 V LiPo battery as the LiPo could explode if shorted and that’s the last thing you want on Halloween.
To cover the contacts, cut small pieces of electrical tape just wide enough so they cover the 4 circle contacts and the surrounding copper area. Don’t fold the tape behind the strip yet as that will make removing the paper for the sticky back much more difficult. It may be easier to do this step after you have soldered all the connections together but I found it easier to put the tape on before it’s soldered because once you solder everything together, you have a really long set of LED’s to handle.
Step 3: Solder Prep Work
When you solder wires to anything, it's always a good idea to pre-tin the wires and the contacts.
First, you'll want to strip about 3-5 mm of the wire insulation off the wires. You can do it with your fingernails but if you have a pair of wire strippers, it's much easier to do that way.
When using a soldering iron, you should always take precautions as the end of the iron gets very hot and could burn you or anything you set it on. In case there is a little solder that splashes for whatever reason, you'll want a set of eye protection as well.
Next, you'll want to tin the end of the wires. Just hold your soldering iron up to the metal with a little bit of solder on the iron so you get good heat contact. Then when the wire has heated up some, add more solder and it should basically get sucked in to the wires and when you have a layer on the outside of it covering the wires, you should be good. Do this for every wire end and also for the 9V battery and JST connector wire ends. This is tinning the wires and makes soldering to something else much easier.
Do the same for the contacts on the LED strips. Just hold the iron to the copper contacts for a little and you should end up with a little blob on the contact that looks like a mound that is flat on the bottom and round on top as the last picture shows. It should be clean looking and not partially soldered. Do this at the end of every LED strip.
Step 4: Solder LED Strips Together
Next, we want to solder each LED strip to the next strip so we can use one power source for all the LED's. You should have pre-tinned the wires so it should go fairly quickly.
As the first picture shows, you'll want to put the red wire right next to the blob of solder on the LED strip with the ( ). Place the soldering iron on top of the tinned wire and it will melt the solder on the wire and will then transfer heat to the solder blob and should melt the blob. Once it melts the blob, the wire should sink right in and then you can remove the iron. Hold the wire still until the solder re-solidifies. Do the same with the black wire on the blob of solder next to the (-). Make sure the red wire goes to the ( ) copper pad and the black wire goes to the (-) pad.
To have an idea of what your solder joints should look like, look at the 3rd and 4th picture. The first is focused on the red wire where the joint doesn't completely cover the wire and is not a good solder joint. The second is focused on the black wire and shows a good solder joint. It's not NASA quality but it's good enough.
Now that soldering basics are out of the way, solder wires in the following order so you can use one battery for the entire set.
1. Solder wires at the top of each leg on the pants.
2. Twist the ends of the red wires together and then the black wires together.
2a. If you're using heat shrink to protect some of the connections, put heat shrink on the red wire and black wire on the female JST pigtail.
3. Solder the twisted red ends to the red wire of the female JST pigtail. Do the same for the black wires.
5. If you're using heat shrink, cover the solder joint you just made and use a hair dryer to cover the exposed wires.
4a. If you're using electrical tape, wrap the joints a few times and make sure the wire is completely covered.
For the hoodie, you'll need to align the LED strips in roughly the location you'll stick them so you have an idea of how long the wires need to be from one strip to the next.
1. At the bottom of the "body" strip of LED's, you'll need to solder the 9 V battery connector and the male JST pigtail on the same set of contacts. Twist the wire ends together and solder it to the LED strip.
2. Solder a set of wires from the top of the "body" strip of LED's. A possible configuration of how to connect everything at that junction is shown in the third to last picture on the step. In that picture, you have the short set of wires that connect the "body" to the "head" but you also have a set of wires soldered at the same point that will go to the right arm to get it power.
3. Solder the wires to the right arm.
4. Add wires to the other end of the "head" LED strip.
5. Finally, solder the ends of the wires you just added to the "head" LED strip to the left arm.
At this point, you'll want to connect the JST connectors together and then your 9 V battery to the battery connector to make sure all the LED's light up. If you soldered everything correctly, all the lights should light up.
Troubleshooting: If all of the LED strips do not light up, check your solder joints and make sure they are good joints. At the same time, make sure all the red wires are connected to the positive ( ) contacts and all the black wires are connected to the negative (-) contacts. If they are, then make sure you have a new 9 V battery!
Once you have ensured all the lights work, go back to every solder joint you just made and cover it with electrical tape to avoid any points that could short out the battery.
Next, you can remove the backing for each strip and when you do, fold over the edges of the electrical tape you put on the other exposed contacts so they stick on the back.
Once that's done, you can stick each strip onto the pants or hoodie. The last two pictures will let you see how I laid out the strips on the clothes. Remember to plug the JST connectors together or you won't get power to the legs!
Now you'll never lose your kids on Halloween night!