Power Bracelet
Make a glowing bracelet!
Electricity is dangerous! Read this caution.
Materials: One piece of paper, scissors, crayons or pencils, transparent tape, copper tape or aluminum foil, a few LEDs, and one 3V watch battery.
Cut the bracelet from a regular sheet of paper or use scraps from the Cube Light project.
Make additional cuts to personalize the bracelet!
Make sure you size it to your wrist (leaving an additional inch).
Design the front side of your bracelet!
Flip the bracelet to the blank side and draw a small "x" where you want your LED lights. Then draw two parallel lines on either side of your "x" marks, extending one side well beyond last "x" mark to provide room for a battery. These lines will become the wires for your bracelet.
Get one piece of copper tape. Gently peel off the back to expose the adhesive and place it over one of your drawn lines.
Caution: Try not to rip or crinkle your tape. You want one strip of tape per side. It can help to cut the tape in advance to match your drawn parallel lines.
Get another piece of copper tape that is about one inch larger than your second drawn line. Remove the backing except on the last inch and secure the exposed adhesive to the other line on your drawing.
After adding both pieces of tape, the back of your bracelet should look like this. The one-inch piece with backing is part of the second "wire." Because the adhesive has not been exposed, it can move around. That non-exposed piece will be used to connect the circuit to the battery.
Image in the Public Domain
Look at an LED:
One lead wire is shorter than the other.
The ridge at the bottom of the bulb has a flat spot above one lead wire (see image).
Each of these conditions identifies the negative lead (cathode)
LEDs work when their positive lead (anode) is connected to the wire from the positive side of a power source and their negative lead is connected to the wire from the negative side of the power source. Determine which piece of copper tape will connect the positive LED lead.
Locate the LEDs you will use for your bracelet and test them by putting their anode (+) and cathode (-) on the respective side of the battery.
With scissors or a hole punch, carefully make holes where your LED lights will be placed.
Because LEDs have a positive and negative side, you may want to add "+" and "-" labels to your bracelet wires.
Bend the leads outward on one LED so you can stick the light through the hole in the bracelet and secure each lead to the copper wire with a piece of transparent tape.
Secure the - LED lead to the - copper wire with a small piece of transparent tape. Then secure the + LED lead to the + copper wire with a small piece of transparent tape.
Caution: be sure that your LED leads are secured to the correct wires or your bracelet will not light.
Connect the battery to the circuit by placing its - terminal on the - wire and + terminal to the + wire. Bend the flap of copper tape (with the backing still on) to complete the circuit. Your LED should light up.
Troubleshoot
If your LED doesn't light
Reverse the battery and see if you reversed the polarity of the LED.
Press the tape securing the leads to the copper. Make sure they are touching.
Make sure the negative wires or battery sides are not touching positive wires or leads.
Wiggle your LED and see if it lights.
When the first LED lights, repeat the process by adding and testing a new LED. Continue until all LEDs are added.
Secure the battery to the bracelet with transparent tape or a paperclip.
Wrap the bracelet around your wrist and secure it with another piece of transparent tape.
Enjoy!
Click to Read What's Happening
A direct current circuit is an electric path that forms a circle. Electricity flows from the battery through a wire to various components (e.g., lights, motors, diodes) and back to the battery. The flow of electricity lights the LEDs on your power bracelet.
Watch this YouTube video to see how your circuit works.
If you added more than one light, you likely made a parallel circuit. This ~4 minute video distinguishes between series and parallel circuits.
Look closely at the copper wires on your bracelet. Notice that they never touch each other directly, even when the battery is connected! Each wire only touches one side of the battery and one LED lead wire. For a circuit to function properly, positive wires should never touch negative wires. If they do, the connection will short your circuit. Short circuits drain batteries quickly and may create heat that can damage your wires.
You can prevent wires from touching each other by adding insulating material between them. Insulating materials do not allow electricity to flow through them easily. Examples of these materials include rubber, paper, plastic, and glass. For paper-based circuits, transparent or masking tape is a good insulator.
Challenge
Paper bracelets are great to begin exploring fabric-based circuits. Before you invest in felt and other components, redo this activity (substituting copper tape with conductive thread). Use a needle to stitch your wires. Ensure you practice stitching your wires with regular printer paper as opposed to card stock or other heavier weight paper.
You can secure the LEDs to the thread by wrapping (or looping) the leads around one tine in a pair of needle-nose or jewelry pliers as shown. Once you have mastered stitching and securing your components (using transparent tape as needed), you can transition to felt-based bracelets.