Ever feel like there aren't enough toys at the intersection of cuddly and terrifying? Wish your stuffed animals could double as weapons? Then I've got the toy for you.

These Laser Tag Stuffed Animals easily transform from being a cuddly night light to the world's softest laser tag weapon.

Check out my laser tag plushie in action!

These deadly plushies, when in "war mode," can be used as laser tag guns. They fire and receive 100% child-safe infrared beams from up to 50 feet away. The plushie's eyes light up different colors when it is shooting or being shot; the plushie's heart fades as it gets shot, acting as a health meter to show how many times the stuffed animal has been successfully fired at. And when you want the toy to turn back into a cuddly night light (entering "warmth mode"), simply push the tail down.

Though these particular laser plushies are meerkats, the CAD models and electronics can be adapted for any stuffed animal with a tail.

Step 1: Preparation

Materials:
Stuffed animal
Sewing kit, velcro
Moldable polyurethane plastic
Aluminum foil
Small springs

Electronics:
Arduino
Arduino ProtoShield
IR LED
IR Receiver
NPN Transistor
3 RGB LED's
Buttons
9 volt battery

Tools:
3D printer
Glue gun
Solering iron, solder

A complete version of my Arduino code can be found here.

Now choose your victim stuffed animal, and get cracking.

Step 2: IR Laser System

IR is the backbone of the laser tag system. The infrared receiver is an IR diode plus some circuitry which makes the receiver sensitive only to infrared pulses of 38 kHz. This blocks out any background infrared from the environment. The IR receiver has three pins: 5v, sensor, and ground. When it detects an 38 kHz infrared signal, the sense pins goes to ground. Otherwise, the sense pin is at 5v.

Now let's drive an infrared LED at 38 kHz so it can interact with our receiver. The simple driver circuit pictured consists of an IR LED, a higher resistance resistor, a lower resistance resistor, and an PNP transistor. Input goes to the collector of the transistor. The base and emitter short when the collector is at a high voltage, allowing current to run through the IR LED. Running the LED with this circuit allows for more current (and thus a stronger IR signal and farther shooting range) than simply connecting the LED from an Arduino output to ground. The circuit diagram and breadboard set up are pictured below. Make sure to connect the transistor's input to the Arduino pin 9! Otherwise the software here will not pulse your LED at 38 kHz.

This code uses direct pin manipulation to oscillate the output pin at precisely 38 kHz.

Once you're comfortable with the circuitry setup, it's time for some stuffed animal surgery. Cut a slit down the back of your plushie, and remove the stuffing (this will make attaching the circuitry easier). Cut two very small slits in the head of our plushie: one for the IR LED, one for the receiver. Before you hot glue the elements to their respective slits, solder several inches of insulated wires onto each pin of the receiver and each leg of the LED. Having longer wires will make it easier to organize/attach to the Arduino. Once you've hot glued the elements to the plushie, you're ready to start adding some RGB LED's!

Step 3: Molding Heart + Eyes

LED's don't shine very well through fabric. A bright but diffused glow can be created by putting an RGB LED behind a molded plastic part. We need three molded pieces: two eyes and one heart.

Use a glue gun to attach an RGB LED into the holes in the back of both molds.

You can print the heart with these files: first half of mold, second half of mold.
You can print the eyes with these files: eye CAD

After gluing the LED's to the molds, solder several inches of wire to each LED lead. Now glue each eye into the eye socket area of your plushie.

Step 4: Controlling the Flashing

Wiring up the heart and the eyes is more patience than thought. The two eye LED's can be soldered together in parallel and controlled by the same output pins.

Here's a diagram of how to solder your various wires to the Arduino.

Here's how this stuffed animal responds to different stimulus:
Warmth Mode:
- Eyes glow blue
- Heart beats green

War Mode:
- Eyes glow red: the meerkat is neither shooting nor being shot at
- Eyes glow blue: the meerkat has just been shot
- Eyes glow green: the meerkat is shooting
- Eyes flash red, green, blue for two seconds: meerkat has been drained of health and is respawning.

Download this code to control your glowing stuffed animal!

Step 5: Putting Together the Trigger

What's a gun without a trigger?

Much of the effort of this project is put into the process of making a good trigger mechanism. The handle is 3D printed into four main parts: the two halves of the handle, the trigger, and the hinge. Place springs inside the main handle compartment. Place a button with soldered wires. Insert the trigger. Epoxy the second half of the chamber to the handle. And voila! A laser tag trigger/handle.

Next is the functionality of switching from war mode to warmth mode with the flick of a tail. A hinge piece is also 3D printed. Glue magnets to and cover both the bottom of the trigger chamber and the hinge piece with aluminum. Solder wires to the aluminum. Attach the wires to the arduino as shown in the diagram from the previous step. Now when the handle and hinge meet (and magnetically lock together), a complete circuit is formed and the arduino knows that it should be in war mode.

You can download all trigger-related CAD files here.

Step 6: Final Touches

Gently fit the circuitry into your stuffed animal. Put as much stuffing as you can back inside, too. Velcro up the plushie, plug in a battery.

Now go play laser tag!

Again, the final arduino code can be found here.