Summertime is great for kid activities. Kids can play soccer, tag, tennis, and frisbee, even after they return from school. What about those long, dark, winter nights? Kids get bored unless they are plugged into the TV.

What if we stop cursing the darkness, but light up the fire of joy? What if the kids can still play all the above games outdoors, only with more fun?

Even better, what if one toy can enable all the above games at night?

And even better, what if kids can build this toy themselves?

And not even that, what if this toy can be built in 20min, at little cost, with mostly recycled materials?

Introducing the kid-proof FireFloam: a Featherweight Gemstone made from foam and a simple circuit.

Comparing with Commodity Glow Balls

Aesthetics: The foam provides great light diffusion and texture, giving it a gemstone look when glowing
Flexible: Can be easily reshaped or sculptured for customization. You can cut it into a frisbee, a star, a cube, etc.
Safe: You can throw it as hard as you can, it will have a soft touch
Attachable: Since it's lightweight, it can be easily attached to other things with masking tape (we tried taping it to frisbee, sticks, clothing...)
Lightweight: It is so light that it can be blown up by a hair dryer!
Easily built by kids.

Supplies

Material:

1 x Foam block Can be reused from packaging foams. It is a type of foam that is translucent and deformable. Not those white, solid blocks. We got our foam from delivery boxes.
1 x Tape Clear or white tape is preferred for aesthetics.
1 x CR2032 button battery holder, or any 3V battery holder that is small and light.
1 x CR2032 battery
1 x Female to Female jumper wires. Short wires are actually preferred.
1-3 LED light-emitting diodes

Tools:

1 x Hot glue gun
1 x Wire stripper and cutter
1 x Scissors / Knife: To cut foam blocks

Step 1: Understand the Circuit

To simplify the project so that it is lightweight and easy to build by kids, we focus on a simplified circuit where the LED diodes work in parallel without any resistors. No soldering is needed.

Here we show an example with two LEDs, you can add or remove LEDs according to your need. Note that the LEDs work in parallel.

There are multiple ways to extend this project. You can add sensors or switches to turn on/off the light for example.

Step 2: Pick the LED Lights

A FireFloam can work with just one LED diode. But why stop at one? You can have multiple colors (I tried two) for a FireFloam!

The caveat is, there are two groups of LEDs. For this post, you can pick one or multiple LEDs as long as they all fall within the same group:

Red and Yellow
White, Blue, and Green

Here is the reason. In this minimized circuit, the LED diodes work in parallel without any resistors. However, LED diodes have different resistances. The red and yellow LEDs usually have a forward voltage of about 2V, while white, blue, and green LEDs have a forward voltage of about 3V. This means, when two LED diodes from different groups work in parallel, like a red and a blue diode, the current will prefer the path with the least resistance (the red diode in this case) and therefore the blue diode won't light up.

Step 3: Wire the Circuit

The images walk you through step by step.

Cut the female-to-female wire in half. Now you have two wires, each has a female pin. One will connect to the negative (shorter) pins of the LEDs, and the other to the (longer) positive pins. You can trim them to be roughly 1.5 inches long each. Since the two wires look almost the same, it will be helpful to mark which is chosen to connect to which LED pin. To do so, I taped the wire for the positive side.
Strip the cut-open side of the wire.
Repeat the above for both wires.
Twist the LED's pin with the corresponding wires' stripped section. If multiple LEDs are used, we should first overlap their pins so that the long pins are aligned on the same side. We can then twist the stripped wire around the pins in the same way. Be careful since such a connection is very fragile.
Do the above to bother the long pins and short pins.
Apply hot glue to protect and strengthen the wire-LED connection.
Plug the female pin of the wire into its corresponding battery holder pins, positive to positive wire, and negative to the negative wire.
Apply hot glue to protect the wire-battery holder connection.

Step 4: Make the Base Foam Block

The size of a FireFloam can be big or small. Here we assume a size of 3 x 3 x 3 cubic inches. It will contain two parts: A 3" x 3" x 2" base to hold the circuit, and a 3" x 3" x 1" cap to cover it.

Here are the steps to cut the base.

Cut the foam block by roughly 3" x 3" x 2". Note that it does NOT have to be perfect. We will refine its shape at the end.
On the square side (3" x 3"), use scissors to cut a hole that is roughly 1" x 1" x 1". This hole is at the center of a FireFloam to place the circuit. Please do not cut through.

Step 5: Cover It Up and Put It Together

Now let's put the batteries inside the battery holder, the LED should light up!

You can now place the circuit inside the base. Make sure it fits. Adjust the size of the hole if needed.

You can now cut a 3" x 3" x 1" cap. Again, it can be bigger, the shape does NOT have to be precise.

Place the cap on top of the base with the circuit inside. Then tape them together. In my case, masking tape worked great with the foam. Don't worry about the scrappy looking, it doesn't matter at night and kids (at least my boys) don't care about it.

Finally, you can do a final polish and cut the corners. Since it is foam, you can shape it to whatever you want. Kids love doing that! We tried to trim it to the shape of a ball.

Note that to turn the lights off, you will have to peel off the tape and take the battery out of the holder, which is not a big deal for us.

Step 6: Be Creative and Play!

Now you have a FireFloam! Make more of them to multiply the fun!

As this video shows, the night we made two FireFloams, we played:

Soccer: Kicking the FireFloam
Tag: Throwing balls at each other is safe because its made of foam
Badminton: Using FireFloam as the ball
Fire Dance: Taping FireFloam to each end of the stick and dance with that stick
Frisbee: By taping the FireFloam to a frisbee
Wind Tube: The FireFloam was blown up by a hairdryer and got suspended in the middle of the air.
Spooky sink: The FireFloam floats on the water in the sink. It dances with ripples and splashes. (Note FireFloam is NOT waterproof, but the circuit is well-protected by the foam as long as nobody pushes it under the water.

Our kids had a blast and they even hold the FireFloam to sleep...

Next thing to worry about: Get some warm clothes so the kids can play longer outside in the dark!

Seize the day, and night :)