Introduction: Blacklight LED Collar
This was made as a gift for my friend Heidi, who has a very particular need. Heidi is a professional painter who lately has been touring the earth with her boyfriend Robert DeLong, painting the faces of everyone in the crowd at his shows with blacklight-reactive paint. Heidi's responsible for the look of Robbie's shows (and created the inspiration for his X logo). You can see tons of crazy examples of her work here.
So Heidi came up with an idea, and asked if I could make it for her: She's often on tour, and has to paint faces in a variety of places that may or may not have what she needs to set up shop. Sometimes there aren't even outlets available. So it would perfect if she could have a wearable piece of electronic clothing that could (a) emit mild UV light when she's working with blacklight-reactive paint on participants' faces, and (b) emit very bright regular light when she needs to either set up or take down her station.
And thus, the Blacklight LED Collar was born.
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Step 1: What You'll Need
This collar is worn as a choker, but is made from a small dog collar from the pet store. (Hey, they're stronger! And I think they look cool.)
Here's what you'll need to make your own:
- Small pet collar or other moderately thick choker
- UV ("Blacklight") LEDs
- Ultrabright LEDs (Warning: These are REALLY bright!)
- A DPDT Slide Switch (Mine is toggle but slide is best)
- Extra Thick Conductive Thread
- Thin Conductive Thread
- Regular, non-conductive thread
- Sewing needles
- A 3.7V LiPo Battery (This battery has a male connector, so you'll need a female connector too to attach it to your project.)
- Micro LiPo USB Charger (This comes with it's own female connector.)
- Basic Soldering Equipment (Iron, Stand, Solder, Wire, Strippers, Cutters, Electrical Tape)
- Needle-nose pliers
Step 2: Get the Electronics Working on a Breadboard (V = IR)
Test all of your LEDs individually with a small button battery before working with them. It's pretty agitating to take all the time to sew them to a project, just to realize they're broken afterwards.
For this step, you're going to need your LEDs' datasheets. Here are the ones that match the LEDs I recommended to you:
UV LED Datasheet (3.0V-3.6V / .016-.018Ah)
Ultrabright LED Datasheet (3.2-3.4V / .016-.018Ah)
Adafruit states that our LiPo battery provides: 3.7V / 150mAh
With this data, we can see that the voltage our battery will provide is roughly in line with what the LEDs want, but the current from the battery is WAY too high for them. If you wire your battery straight to your LEDs in this state, you will very quickly burn them all out. So, how do we fix this?
Let's tackle voltage first:
A good tip to remember is that wiring LEDs in series will divide the voltage across them, but wiring them in parallel will not. Since all of our LEDs want roughly the same amount of voltage that the battery provides, we'll wire them in parallel. This way, they'll all receive 3.7V.
V = IR is all you need now. You know your voltage, and you know the current you want through each LED, so solve for R to figure out what resistor you need in your circuit. But note that I tested my LiPo battery, and am actually receiving 3.9V, not 3.7V like the datasheet says. Always test first, and base your calculations off of reality.
If you're unsure of your ability to accurately use (V = IR) to determine what resistor to use in your circuit, I'd recommend this:
1. Wire up your LEDs as desired, and grab a resistor with moderately HIGH resistance. (Start with 10K, or 1K.)
2. Grab a multimeter and see what current is running through your LEDs.
(a) Is it too much? (Probably not.) Get a higher resistor.
(b) Is it too little current? Get a lower resistor.
3. Rinse, repeat until the current running through your LEDs matches what the LED datasheets require.
Step 3: Prepare the LEDs for Sewing
There are snazzier ways to attach LEDs to wearables than this. (For example, you can buy surface-mount LEDs that are soldered on to tiny, easily-sewable pads.) But I think this way looks cooler.
Grab some needle-nose pliers, and twist the metal leads on on your LEDs around the tiny tip of the pliers. Try to make them flat enough to stand up on their own. Do this to all of your LEDs.
(Pro tip: It's VERY easy to confuse the UV LEDs with the Ultrabrights, since they look identical. Pick up an LED, and look STRAIGHT DOWN through the top. You should see a faint yellow tint inside of the Ultrabrights. The UVs should look clear from the top. Use this trick when you inevitably set one down and forget which it is.)
(Pro tip: It's also very easy to forget which side of your LED is positive and which is negative--especially with the leads all curled up! Here's a nice explanation on how to see which end is which without using the leads.)
Step 4: Sew Your LEDs and Resistor to Your Collar
Grab your THICK conductive thread. Lay two pieces of it on your collar, parallel to each other, and sew it to the collar with normal, NON-conductive thread. These will be the traces that you will sew your LEDs to. Leave about an inch of loose thick thread on the right side of both pieces. Now grab some wire, strip about a quarter inch of insulation off of the end, make a little wire loop at the end, and run your thick thread through the loop. Hold the thread taught, lay it back down over itself and sew it tightly down against your collar with thin conductive thread. The wire should now be tightly bound against the thick thread. You can't solder conductive thread, so sewing it through a loop in your wire is an "almost-as-good" way of attaching them together. Do this again on the other piece of thick thread, but make sure to add a resistor in there as well. (See the picture. Don't add the switch yet! Sorry that it's in the picture already.)
Now grab your THIN conductive LED thread, and your LEDs. I chose to set up my LEDs in an "every other" pattern. (e.g. LED1 is UV, LED2 is normal, LED3 is UV, LED4 is normal, LED 5 is UV, etc...) You're now going to use the thin conductive thread to sew the LEDs up against the thick conductive thread.
BUT WAIT! Now is the time where polarity REALLY counts! We want our collar to have three settings, controlled by a switch with three positions:
(1) UV LEDs on / Regular LEDs off
(2) UV LEDs off / Regular LEDs off
(3) UV LEDs off / Regular LEDs on
In order to do this, we're going to have to set up our LEDs carefully. I'll explain more in the next step, but for now, sew all of your UV LEDs with the negative lead on the bottom, and all of your Ultrabright LEDs with the negative lead on the top. To make your life easier, sew all of the UV LEDs on first and leave gaps between them. (In my picture, I'm trying it on at this step to make sure it looks ok.) Once you're done, then go back and sew on all of the Ultrabright LEDs in the opposite direction.
Step 5: Sew on Your Switch and Solder It
We picked a DPDT switch with 6 leads on the bottom for a very good reason: These switches allow you to easily reverse the polarity of the current running through your circuit. This means that current runs in one direction while it's in position one, no current at all runs in position two, and current runs in the opposite direction in position three. Since LEDs are diodes, they only accept current in one direction. This means that your LEDs with the negative leads facing up will turn on in position one, no LEDs will turn on in position two, and the LEDs with the negative leads facing down will turn on in position three. This is what enables us to turn on the UV LEDs and the Ultrabright LEDs separately.
Solder your wires to your switch like mine, and attach the female plug (the white thing on the right in the picture) for your battery to the other end. The female plug should have come with your battery. If not, you can grab them from Fry's or other hobby electronics stores.
If my picture is too fuzzy, check out this instructable for more details on how to wire the switch.
Step 6: Your Battery and Charger
Here's a quick look at the battery and the charger.
I chose to tape the battery to the collar, just in case I ever need to replace it. In the picture, you can see what it looks like when the battery is not attached to the LEDs, but is attached to the charger. In this state, you can plug your collar into the USB port of your computer and charge it up! Once it's done, just remove the charger and plug the battery back into the LEDs.
Step 7: You're Done! Try It Out!
Once your battery is charged (the light on the charger will turn green), take your charger off, and plug the battery into the collar. Try all three positions on your switch to make sure that you get UV LEDs in one position, no LEDS in the middle position, and Ultrabrights in the last position.