Turn your sound on, then press play.
Each student needs one straw, one battery, and one LED to make one Glow Blade. The first three items open a shopping search on Amazon.
Your Glow Blade has no plug and no wires you can see. So how does it light up? The secret is a tiny loop called a circuit.
A circuit is a complete, unbroken loop that electricity can flow around. Electricity flows out of one end of a battery, through whatever you connect, and back into the other end of the battery. If the loop is broken anywhere, even by a tiny gap, electricity cannot flow and nothing happens.
Every battery has two ends, called terminals. One is marked positive, shown as a plus sign (+). The other is negative, shown as a minus sign (−). Electricity needs both ends connected to complete the loop.
An LED stands for Light Emitting Diode. It is a small bulb that turns electricity directly into light, without getting hot like an old-fashioned light bulb. That makes LEDs perfect for a handheld blade you hold right in your hand.
A circuit is closed when the loop is complete and electricity can flow. A circuit is open when there is a gap somewhere and electricity cannot get through. Flipping a light switch at home opens and closes a circuit. Your Glow Blade will use the same idea, except you will build the switch yourself.
A system is a group of parts that work together to do a job. A circuit is a system. The battery, the wires, and the LED all have a job to do, and every single part has to connect correctly or the whole system fails. Keep an eye out for that as you build.
Look closely at an LED and you will notice two metal legs sticking out the bottom. They are not the same length, and that is not an accident.
The longer leg is called the anode. It connects to the positive (+) side of the battery. The shorter leg is called the cathode. It connects to the negative (−) side. Get them matched up correctly and the loop is complete.
Here is the part that surprises most builders: an LED only lets electricity flow through it in one direction. Connect it backwards, and no electricity flows at all, so it will not light up, even though the circuit looks complete. It is like a one-way gate for electricity.
Connecting an LED backwards does not hurt it and does not hurt you. It just stays dark. If your LED will not light up, the very first thing to try is flipping it around. Builders do this all the time. It is part of the job.
A coin cell battery has a flat positive (+) side and a flat negative (−) side, usually marked right on the metal. To light your LED, touch the long leg to the + side and the short leg to the − side at the same time.
If you look up other LED projects, almost every single one uses an extra part called a resistor. Your Glow Blade does not need one. Here is why.
Bigger batteries, like AA, AAA, or 9V batteries, can push a lot of electrical current very fast. An LED is tiny and delicate inside. Connect it straight to one of those big batteries and too much current rushes through it at once. The LED can burn out instantly, or even pop.
A resistor is a part whose entire job is to resist, or slow down, the flow of electrical current. Adding one between a big battery and an LED keeps the current down to a safe level, so most LED circuits need one to survive.
A coin cell battery is small and can only push a small, gentle amount of current, even at full strength. Engineers describe this using a trade-off: a coin cell gives up a lot of power in exchange for being small, light, and safe to connect directly to an LED.
Every battery has some internal resistance, like water trying to squeeze through a hose. A big battery is like a wide hose: lots of current gets through fast. A coin cell battery has much higher internal resistance, more like a thin straw: only a trickle of current can get through, no matter what you connect to it. That built-in limit is exactly what keeps your LED safe without needing a separate resistor.
Pick a battery and see what happens when you connect it straight to an LED with no resistor.
Your Glow Blade needs a switch, but there is no room inside a thin straw for a store-bought switch. So you are going to build one using nothing but a gap and your own fingers.
Remember Mission 1: a circuit only works when the loop is complete. A switch is simply a part of that loop you can open and close on purpose.
Here is the trick. You tape only one leg of the LED to the battery, leaving the other leg sitting close by, but not touching. That small gap is an open circuit, so the light stays off. When you squeeze the straw right where the battery is, you press that second leg against the battery, closing the gap. The circuit completes, and the light turns on.
Let go, and the leg springs back away from the battery. The gap reopens, the circuit breaks, and the light turns off again. Squeeze and release, squeeze and release, that is your whole switch.
Tap a leg to tape it down. You need to find the setup that actually works as a switch.
The building steps open when every mission is finished. Here is what you still need to do:
You earned it. Go slowly and follow each step in order. Check the box when a step is done.
You need one short piece to be the handle, and one longer piece to be the glowing blade. Cut your straw so the handle piece is about 2 inches long, and the blade piece gets the rest.
Hold the battery between the two LED legs so each leg touches one side. Remember Mission 2: the long leg goes on the + side. It should light up right away. If it does not, flip the LED around and try again.
This is the step that builds your switch. Tape just one LED leg flat against one side of the battery. Leave the other leg nearby, but do not let it touch. That gap is what makes it a switch instead of an always-on light.
Push the battery and both LED legs down into the short straw piece. Go slowly so the tape does not slip off. A pencil eraser or the back of your scissors can help press it the rest of the way down.
Squeeze the straw right where the battery sits. The light should turn on while you squeeze, and turn off when you let go. If nothing happens, open it back up and check that the untaped leg is close enough to touch the battery when you squeeze.
Slide the longer straw piece over the top of the LED, so it covers the little bulb like a sleeve. This is the piece that will glow.
Wrap electrical tape around the handle and the spot where the two straw pieces meet. This holds everything together and keeps the blade from sliding off.
Your Glow Blade is finished. Squeeze the handle to light it up. Let go to turn it off.
| What happened | Why | Try this |
|---|---|---|
| Nothing lights up, even before taping anything | The LED is backwards | Flip the LED around. The long leg needs to touch the + side. |
| It worked loose, then stopped working | The taped leg slipped, or the battery shifted | Open the handle back up and re-tape the leg firmly against the battery. |
| It stays on all the time, even without squeezing | Both legs are touching the battery | Check that there is a real gap on the untaped side. That gap is your switch. |
| It never turns on, no matter how hard you squeeze | The gap is too wide for the leg to reach | Gently bend the untaped leg a little closer to the battery. |
| The blade piece keeps sliding off | The tape is not holding it tight enough | Add another wrap or two of electrical tape where the two straw pieces meet. |
Write three or more sentences. What happened the first time you tested your LED? Did you ever have it backwards? How does the squeeze switch actually work? Use at least two of these words: circuit, anode, cathode, resistor, switch.
Big idea question: your Glow Blade is a system. Which part would stop the whole thing from working if it failed?
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