The Bluefruit Blademaster (Touch-Activated Customizable Saber)

I made a capacitive touch-activated foam sword that lights up like a lightsaber and reacts to when you swing it. I've always loved playing with foam swords, the upper echelon of such being the high-tech lightsabers some hobbyists would use. This was my (first) attempt at making something comparable.

Microcontroller: Adafruit Bluefruit Playground

LED Strip: 1M NeoPixel Digital RGB LED Strip

Power Supply: Adafruit Industries 3 x AA Battery Holder with On/Off Switch (does not come with AA batteries, please grab some)

Fabrication Materials: Foam (either 1/2 inch or 1 inch thick) (EVA preferred, although other foam types can work as well), wires, spray paint (optional), tape, conductive copper tape / copper wire

Machines (optional): Laser cutter

As you can see in the images, the first step (the fun one) is to design your sword! I started by sketching a hilt on half-inch thick EVA foam board. In the center of the hilt, you can see tracing of both the Adafruit Bluefruit Playground and the 3xAA Battery Holder - this is to ensure they will fit in the hilt during assembly and fabrication.

Next is the blade - length of the blade will depend on the length of your light strip. Keep in mind that it should be a little longer than half of the length of the light strip you will use as you must fold the light strip in half while it sits in the blade. In my instance, this made my blade 21 inches long. I slightly tapered the end of the blade so that it would look more like a sword blade, as can be seen in the Illustrator document *blade1.ai*

Ensure that your handle is not too thin (mine broke on a particularly strong swing), and think about how your blade will connect to your hilt. I would recommend making a small indent in your hilt where the blade will sit such that you can glue the blade into the small indent.

1. Setup & Initialization:
2. Imports libraries for BLE, LEDs, touch, sound, and sensors.
3. Initializes the NeoPixels, touchpads, speaker, and accelerometer.
4. Starts BLE advertising, waiting for a mobile app to connect.
5. Color Handling:
6. The sword starts with a default blue color.
7. It can change color by touch (cycles through a list), or via BLE from your phone.
8. Make sure the lights light up on both the first and last lights and scale into the middle - this will allow your blade to light up like a lightsaber.
9. States and Behavior:
10. The sword runs in four states: OFF, POWERING ON, IDLE, and POWERING OFF.
11. Tapping the main touchpad transitions between OFF and ON with animated lights and sound.
12. When ON, it constantly animates the blade and listens for motion.
13. Motion Detection:
14. If it senses a quick movement (swing) via the accelerometer, it plays a random sword swing sound.
15. There's a cooldown so it doesn't trigger constantly.
16. LED Animation:
17. While idle, the blade glows with a shimmering wave using a sine function.
18. The brightness subtly pulses over time.
19. Error Handling:
20. If anything goes wrong, it catches the error and flashes the LEDs red in a loop to indicate a problem.

I've attached my code below as an example, however I strong encourage everyone to try making this in their own way. A state machine is just one way of many that this could be done. I also encourage anyone building this to integrate the BLE - it's really fun to change the blade color with your phone.

The electronics in this system are managed entirely by an Adafruit Bluefruit Playground.

1st, plug your Adafruit Bluefruit Playground into the 3xAA battery pack via the JST PH 2-pin connector that is wired to the battery pack. While running, this battery pack can run the whole system for around ~10 hours.

2nd, connect your NeoPixel strip to your Bluefruit. Your black wire should go to the GND (ground) connection, your red wire should go to the VOUT (which will have a voltage of ~4.5v when connected to your 3xAA battery pack), and your white wire should go to an information pad such as A5 (or whatever you programmed your light pad as).

At this stage you are able to test your code. You can also plug you Bluefruit into your computer for power and for easier code changes. Test to make sure that everything works as intended by tapping your conductive pad (I used A1). If sound plays, and the light strip powers on/off, you're good to go. I found it helpful to write error reporting and print statements into my code so that while I was working with my Bluefruit plugged into my computer, I had a better idea of what was happening.

This was by far the most difficult step for me. I have not done much fabrication before this and I realized very quickly that this was going to take the most amount of time. Assuming you have your electronics done however, you're good to start experimenting!

Firstly, I highly recommend using EVA foam, or at least some other foam type which can be laser cut. Laser cutting (if you have assess to it), makes this entire project so much faster and easier.

We did not have settings for foam on the laser cutter yet so much of my time was spent figuring out what settings to use. I found that 30% power at 2.5% speed on the Speedy 360 would cut about 1/4" of foam. Multiple passes worked well, however it leaves noticeable lines where each pass starts and ends. These are easily sanded away. Being able to cut only 1/4" is super helpful when hollowing out the center of the blade to make room for the lights.

When designing your blade and hilt, keep in mind how the electronics will be sitting inside of them. By leveraging the laser cutter's ability to cut partially through the foam, you can create near-hollowed out cavities which you can then fully hallow out. You can achieve this by creating concentric rectangles (or whatever shape you'd like) that will be cut with the laser at whatever depth you desire. This will get rid of about half of the material in the area you'd like and weaken the rest such that you can scrape and cut out the rest. I'm sure with more experimentation the engrave feature would also work for this however I was not able to get it work so far.

When working with your blade, cut a rectangle out the length of most (not all) of the blade and the width of your light strip. Then fold your light strip in half and use tape to secure the light strip folded in half within the blade. Ensure that it is folded exactly in half, so that when it turns on it will light both sides up evenly.

After laser cutting your blade and hilt, mount your Bluefruit and battery pack into your hilt in the cavities designed for them. Make sure the battery pack is switched on. Once mounted, cut a small slit in the hilt between your Bluefruit and your handle. Wrap the handle in copper tape or any other connective material, and run a wire from your conductive pad (in my case, A1), and your handle. Connect the conductive handle and said wire. This will allow your blade to turn on when you touch the handle.

Now, if you wish, connect a small piece of conductive material to the bottom of your hilt, at the pommel. I wired this through the middle of my hilt, however you can wire it along the side as long as it is insulated from the conductive material that surrounds the handle. Connect this to your "color change" pad (I used A2).

Finally, take your blade with lights mounted and wire this to your Bluefruit. I used alligator clips for this, however I highly recommend a better wiring system such as soldering it or using copper wire, due to the alligator clip's large nature. Once you've connected the red wire to VOUT, the black to GND, and the white to your light pad (I used A5), glue your blade (or attach in another way) to your hilt. Once this dries, decorate however you like, and you're good to go!

Your Bluefruit Blade should now function as intended.