LED Jumper Wire Bracelet W/Magnetic Clasp

Since I love elegant wiring, I thought that for the Jewelry contest, I could combine the two worlds of wearables and circuits by making a functional LED bracelet with jumper wires, a CR2032 battery, and some LEDs! The lights and battery are optional, so if you just want to make a decorative bracelet, you can skip them. You can either use a piece of boxboard or a flexible 3D printed piece for the base of the bracelet, but I would recommend a 3D printed part as it'll last much longer.

Note: These are not affiliate links. I just tried to find some of the cheapest, most sensible options for the things the project needs. For items preceded by an asterisk, the specific brand, model, or attribute is important, so I would recommend you purchase the specific linked item. For tools, I linked the tool I used for the project, or a comparable tool if I couldn't find mine online.

Things You Need:

-*Jumper wires

-*Flexible TPU filament OR boxboard

-*Magnets

-Hot glue

If you want to add LEDs, you need:

-3V LED lights

-CR2032 battery

-*Battery holder

-Electrical tape

-Solder wire

Tools:

-Hot glue gun

-Pliers

-Scissors

-Flexible ruler (to measure your wrist)

-Soldering iron (if using LEDs)

-Wire strippers/precision blade (if using LEDs)

-3D printer (if using 3D printed base)

If you're using a 3D printed base, you'll need to custom-model it to fit your wrist properly. Instructions on how to do so can be found in Step 1! If you want to make a boxboard base, jump to Step 2.

VIDEO: https://www.youtube.com/watch?v=tbQpUlgXRaA

Again, if you're planning to use boxboard, you can skip this step. I used Tinkercad for my 3D modeling, but any software should work fine. Each picture is numbered based on which step it corresponds with.

1. Create a cylinder with a height of 1mm and a diameter of 24mm.
2. Create a 1mm tall, 24mm wide rectangular prism. The length of the prism should be equal to your wrist's circumference plus 10mm. My wrist measures 175mm, so my rectangular prism will be 185mm long.
3. Line up the rectangular prism with the cylinder so that the prism's short edge cuts the circle in half down the middle.
4. Add another 1mm tall, 24mm diameter cylinder to the other end of the rectangular prism. It should intersect with the prism in the same way as the other cylinder.
5. Group all 3 shapes and download your model as a .stl file.
6. Print the strap in TPU 95A at 100% infill. Step 2 is for a boxboard strap, so you can jump to Step 3!

VIDEO: https://www.youtube.com/watch?v=_eIOWONJpnY

To make a boxboard base, first cut out a long, 24mm wide rectangular strip of boxboard. The length isn't important yet, just make sure it's definitely longer than your wrist's circumference.

Next, draw a little circle on one end of the strip. Make sure the circle's edges are touching the edges of the strip. Cut off the corners of the strip along the circle so that the end of the strip is rounded. On the other end of the little circle, draw a line that is perpendicular to the strap's long edge.

In order to find out where to cut the strip, wrap it around your wrist, and tighten it until it feels comfortable. You might need to hold it down with a piece of tape. Now, look at the little circle you drew earlier. Look at where the perpendicular line you drew lines up with the uncut end of the strip. Draw a line across the uncut end at that point.

Cut along the line you just drew. After cutting, cut the corners of the square end so that it looks the same as the rounded end. Double-check that the strap is the right size by lining up the two imaginary "circles" and checking how tight it feels on your wrist.

VIDEO: https://www.youtube.com/watch?v=YITZqE49hhk

Magnets are how your bracelet will clasp around your wrist, so it's important that you put them in the right places! Luckily, this is quite easy to do. Each end of your boxboard or 3D printed strap will be rounded. Imagine that there is a little circle that lines up with the rounded edge (you may have drawn them already). Glue a magnet in the middle of one of the circles.

Now, flip the bracelet over. Glue a magnet in the middle of the circle that is on the opposite end than the one with a magnet already. This will allow your bracelet to clasp onto your wrist with both the magnets in contact. Test that it fits by clasping it onto your wrist. If it does, you now technically have a bracelet! But it's not a very fun bracelet yet. If you're using LED lights, go to the next step. If not, skip to Step 7.

VIDEO: https://www.youtube.com/watch?v=YM0aGhofYuo

All you need to do to attach the battery box to the strap is put some glue on the back and stick it to one end of the strap! The curve of the battery box should line up with the curve of the strap's end. However, you need to make sure that it's oriented so that the side that opens is exposed. If it's the other way around, you won't be able to change your battery.

The next part is a little tricky. You need to cut and strip the battery box's red wire so that you can wrap it around the side of the bracelet and reach the magnet. If you don't have any flexible jumper wires at home, save the piece you cut off as it'll be useful when connecting to the other magnet.

Then, you need to solder the wire on, or cut a very thin piece of electrical tape and use it to tape the metal end of the wire to the side of the magnet. Make sure the circular face of the magnet is exposed. Doing this makes it so the bracelet's LEDs turn on when the magnets clasp together. If soldering, use hot glue or electrical tape to insulate the connection afterwards.

VIDEO: https://www.youtube.com/watch?v=55dCLH8BYyI

This step is where you get to be creative with your bracelet! First, pick a few spots for some LEDs to go on your bracelet. They should be on the same side as the battery box. Then, extend each LED's legs so that they lay parallel to the surface of the strap.

IMPORTANT: Don't do any soldering yet! First, figure out where you want each and every wire and LED to go. It'll be far easier to solder when you already know where everything is placed.

The wiring for this is simple. Each LED's short leg (cathode) needs to be connected to the black wire on the battery box, and each LED's long leg (anode) needs to be connected to the magnet that is on the same side as the LEDs. One important thing to note is that the LEDs must be connected in parallel (all connected to the power source individually) and not in series (connected to each other with only 1 cathode and 1 anode connected to the power source).

When doing this, don't forget to have some fun with your wires! Use some pliers to bend them into fun patterns! You should also feel free to add some extra wires into the mix that aren't connected to anything, just for fun. The wires also don't need to cover the whole bracelet. If you want, try experimenting with layering wires to add depth to the design.

If you don't have any flexible jumper wires, I would recommend using the bit of the battery box's red wire you cut off to connect to the magnet, and then connecting all the jumper wires to that wire, as they are less flexible.

VIDEO: https://www.youtube.com/watch?v=cSRhkPy7MqA

IMPORTANT: Soldering irons are very, very hot. Be careful!

Once you've figured out where all of your wires and LEDs are going to go, you can start soldering! All you need to do is make sure each wire/wire or wire/LED connection is nice and secure. However, don't solder anything to the battery box's black wire or the magnet's wire yet. You'll do this when you attach the wires to the bracelet.

One everything is soldered together, bend the bracelet and clasp the magnets together. Bending the bracelet before the wires are glued on prevents the wires from all breaking off when the bracelet is worn for the first time.

Now, you can use some more hot glue to attach the wires and LEDs to the bracelet! Bend the wires around the bracelet as you glue them on. Make sure you do this slowly to prevent anything from breaking. Once everything is glued on, make the final solder connections by soldering the anode wires to the magnet wire and the cathode wires to the battery box's black wire. Once everything is attached, insert the battery.

Step 7 is for if you're not using LEDs, so you can skip to Step 8!

VIDEO: https://www.youtube.com/watch?v=4kiwOI1g3QQ

The wiring step is a lot easier when you don't need to make it functional. All you have to do is arrange your jumper wires in a pattern that looks pleasing! There's no need for them to be connected, or for them to be arranged neatly at all. Just do whatever you want! You can use a pair of pliers to bend the wires while you're arranging them.

Once you know where you want everything to go, you can glue them onto the bracelet. If you want to ensure that your wires won't fall off when you bend your bracelet for the first time, I would recommend attaching the wires while the bracelet is bent. However, this is a little tricky, especially when the wires aren't attached to each other.

Hooray! Your bracelet is finished! If you decided to make the LED version, the lights should come on when you clasp the bracelet. The battery should last a long time depending on how many LEDs you used, and luckily it's easy to replace when it runs out. Whether you made the LED version or not, the jumper wires will look pretty cool, especially if you used a fun pattern or color scheme!

Overall, I thought this was a super fun project! I love the way the lights turn on when I put the bracelet on my wrist. In my first design, the jumper wires didn't look nearly as neat, so I'm glad this one turned out better. In the future, I think custom PCBs or a slightly more comfortable design would be cool to experiment with! Hopefully you like your bracelet as much as I like mine, and thanks for reading my Instructable!