Backpack with animatronic tail and RAWR mode with light up Red Glow Monster Menacing Eyes™

If you are annoyed with the incessant howling, install a switch to turn off the sound. A paws button would be convenient.

It’s gone to plaid.

Step 1: The Tail That Wags the Werewolf...

Again, another project because it was raining outside...

I had stocked up on a "pelt" of craft fur I had found at the discount fabric store a while back. I guess it's time to do something with it.

When you are cutting craft fur, use a razor knife on the back of the fabric to cut. It minimizes the amount of loose fibers that get all over the place. Using scissors will give the cut line a bad jagged haircut. Comb or pull away the loose fibers on the cut edge now to make things a little bit neater when you work with that piece.

Taking inspiration from the Adafruit Really Simple Animatronic Tail project, I learned that you should use a piece of aquarium air line tubing for the tail to give it that fluid tail-like motion. I glued up some cardboard to make an upright mount for the servo. It helps during testing to determine and secure the orientation of your servo while the tail hangs and moves below.

I would just need to sew a tube of craft fur to make the cover for the tail. I have a serger which makes easy work of seaming, trimming and binding an edge all in one pass. You could use a regular sewing machine too.

Also from my collection of fabric remnants was some plaid batted quilting cloth and a nonwoven material to use as the backpack liner fabric.

Step 2: Conjure Up Some Electronics...

The Adafruit Circuit Playground Express board has lately become my go-to board for prototyping really quickly. Using Circuit Python and the Mu Editor, I can adjust code to make things work as I go along.

I took a look at the Arduino code for the Simple Animatronic Tail and the pendulum mechanics/algorithm seemed just a bit to complex for me to translate into Circuit Python at the moment. That code was also using servo timing instead of angles to drive the servo. The Circuit Python examples I worked with allowed me to specify angles to move the servo.

I knew I had to drive a servo and wanted some Neopixel lights for some hidden eyes. That I have done already in Circuit Python so I could start from there.

I wired up two Neopixel sticks (8 Neopixel row on a single circuit board) with both their Data IN driven from a single pin. This simplifies code and they will light up in sync from the same command.

To animate the tail in a more life-like fashion, I implemented a lot of random timing intervals and random number of repetitions for the tail movement.

The eyes will randomly flash or stay on and then the tail wags.

The Circuit Playground Express board is also capable of playing small sound clips. I found a howling wolf .wav file I liked. There was not enough room on the board's memory to load the sound file. I used Audacity to downsample the sound clip to a low 16khz. It still sounded OK. It was only going to be played through the onboard piezo speaker so sound quality was not really a big concern. It still wouldn't fit so I had to delete a lot of the .mpy library files for unused devices. I finally got it to save.

My Circuit Python code is here: https://gist.github.com/caitlinsdad/3867563a2332c8...

Step 3: Strap It Down...

When looking at backpacks, you want the straps to be functional, comfortable to use and above all, stylish. The backpack will turn out looking like you're getting mauled by a werewolf with the paws over your shoulders. Kawaii!

I had some 1 inch wide webbing and some plastic Fastex adjustable buckles to use. You can get the one piece sliding adjustable buckle if you don't want the quick release function where the buckle separates.

Lay out how you are going to make your shoulder straps.

I will have a padded plaid top part with craft fur tips. The adjustable buckle will be hidden by the paws.

Cut the webbing pieces to size. A small piece of webbing will fix the buckle in position right under the paws. A longer length is the adjustable strap that is fixed at one end to the bottom of the backpack. Seal the cut ends.

Create a tab cover for the bottom strap to make it easier to embed that strap to the bottom of the backpack.

Here is where you have to figure out how to seam everything and piece together your fancy shoulder strap.

Slice the excess fabric covering the paws for that authentic shredded flannel shirt look.

Step 4: Wear It Like a Boss...

Usually when you are constructing things like this with sewing, you are sewing on the inside of the article so that you get nice finished seams on the outside. Everything gets turned inside out,

I started out piecing together enough liner fabric to cover the inside of the the backpack.

I then mated the liner fabric to the outer plaid fabric. From there it was mocking it up to find the right size to make the backpack and saw that the excess fabric naturally created a cover flap for the backpack.

I trimmed the cover flap edge with some craft fur. It has a slight chevron shape to make it animal-like.

When seaming the sides of the backpack, don't forget to embed the end of the adjustable shoulder strap to the bottom corner of your backpack.

I bar tacked the two shoulder straps - paws to the bag and fed the already attached bottom straps through the Fastex adjustable buckles to complete the shoulder straps.

Step 5: Aiwoooooo....

Cut out and reinforce the opening where the tail mechanism sticks out through the backpack. Install the electronics in the backpack.

One last detail I added was to install a few eyelets on the top edge of the opening of the backpack. I ran some paracord through it to create a drawstring closure for the top. There is a plastic drawstring lock on the free ends to secure it closed. You don't want your stuff falling out of your backpack on the way to Grandma's house.

I didn't make use of the onboard Neopixels available on the Circuit Python Express board itself. Anyone out there for an Iron Man Arc Reactor Werewolf?

Maybe add GPS and datalogging to see where you've been all night.

How about a Full moon detector and water bottle holder?

Enjoy!