Robotic Paper Octopus (with Micro:bit)

Make a grumpy paper octopus that retracts its tentacles in reaction to loud noises!

Supplies

Electronics:

micro:bit v2

Crazy Circuits Bit Board

LEGO Compatible 360 Degree Servo

2 AAA Battery Holder

Other:

Cardstock (3 sheets)

Sewing Thread (preferably a thicker one that's more durable)

Cardboard (you only need a small amount; a 5" x 5" piece will work)

Printable Template (in the PDF link below)

Tools:

Glue

Scissors

Sewing Needle

Step 1: Making the Tentacles

• Cut out a tentacle
• Fold it in half with the template markings on the outside
• Tip: You can save some time by folding the tentacle in half, then cutting the rounded top part

Step 2: Poke the Holes

• Use a sewing needle to make the holes in the marked locations
• Make sure to go through both layers of paper

Step 3: Invert the Tentacle

• Fold the tentacle in a zig-zag
• Unfold the tentacle, then refold it inside out so the template markings are on the inside
  • You can also leave the template markings on the outside if that's your style!
• Optional: add glue when you fold it in half to hold the two layers together (it's not necessary since it holds its shape pretty well without glue)

Step 4: Cut and Knot the Thread

• Cut a piece of thread around 12" long
• Double or triple knot the end of the thread
• Thread the needle

Step 5: Sew the Tentacle

• Use the holes you made in step 2 to sew the thread through the tentacle
• Make sure to start from the rounded end of the tentacle, and on the outside of the zig-zag fold
• Add a drop of glue (or tape) on the knot to make sure it doesn't pull through the paper
• Double check that the knotted end is on the rounded side of the tentacle, and the extra thread is on the opposite side

Step 6: Make More Tentacles!

• Repeat 7 more times until all 8 tentacles are finished
• Set the legs aside for now to let the glue dry
• Are you regretting making a robot with 8 legs? Just be glad it's not a centipede!

Step 7: Making the Body

• Cut out the template for the body and top
• Fold the body following the markings on the template

Step 8: Assemble the Top and Body

• Glue the body into an octagon shape (the two sections on either end should overlap on top of each other to form 8 sides)
• Glue the top on to the tabs
• Tip: I found it easiest to flip the body upside down while I was gluing the tabs in place

Step 9: Alternative Body

• If you're feeling up to a challenge, you can also make the body using the origami method, which results in the twisty-top on this Octobot
• I used the instructions here to create an Origami Octagonal Box: Origami Octagonal Box

Step 10: Cut the Base

• Use the base stencil octagon to trace an octagon onto a piece of cardboard
• Cut the base octagon out of cardboard
• The base should be just small enough to fit inside the body (but not so small that there's loads of empty space around it)

Step 11: Attach the Tentacles

• Glue a tentacle to the bottom of the cardboard base
• Only glue the last folded section of the tentacle (the one without a hole)
• Make sure the thread doesn't accidentally get glued to the cardboard

Step 12: Add the Other Tentacles

• Repeat for the other 7 tentacles
• Try to keep the threads from getting tangled

Step 13: Make the Servo Holder

• Cut the servo holder template
• Fold the servo holder
• Glue it around the servo
• You don't need to glue the paper to the servo—just wrap the servo holder around the servo, and glue it where the two parts overlap

Step 14: Attach the Servo

• Glue the servo holder to the cardboard base of the Octobot
• Note that the servo itself isn't centered on the body—the servo's shaft is what should be approximately centered

Step 15: Making the Axle

• Cut a piece of straw about 3/4" long
• Use the needle to poke a hole through the straw at about halfway between the top and bottom
• Poke another hole (this one only needs to go through one wall) close to the top of the piece of straw

Step 16: Check the Straw Size

• Put the straw onto the servo shaft
• Since straws come in all different sizes, it may be too big. If that's the case, put a very small piece of tape around the servo shaft to increase its diameter
• The straw should fit snugly on the shaft

Step 17: Attach the Thread

• Sew one of the pieces of thread onto the straw
• First go through the middle holes, then up out the top

Step 18: Do It Again

• Repeat this 7 more times until all 8 pieces of thread are sewn into the straw
  • It's best to do this one piece of thread at a time to avoid them getting tangled or twisted
• Check that the length of the thread between the straw and the tentacles is roughly the same
  • You can check this by pulling the piece of straw up to check that the threads are all roughly the same tensions

Step 19: Attach the Axle

• Push the straw to the servo shaft, making sure it's snug (if it's loose, the shaft will just spin inside the straw without turning the straw itself)
• Make sure the tentacle are all fully extended, then tie a big knot where the threads exit from the straw
• Trim the extra thread

Step 20: Connect the Circuit

• Connect the servo to the Bit Board at Servo Pin 1

Step 21: Upload the Code

• Upload the code from here: Octobot Code
• You'll note that the sound activation requires touching the logo at the same time. That's to avoid accidentally triggering it if you're in a noisy environment. You can change that by getting rid of the "logo is pressed" block
• The sound trigger requires using the micro:bit v2. If you don't have the v2, there's loads of other ways you can trigger the Octobot, such as using the accelerometer to shake the micro:bit, or making it light-sensitive

Step 22: Test It

• It's easiest to test the mechanism while the servo is still exposed
• Use the A and B buttons to try retracting and extending the tentacles
• Tip: For the TentacleAction function, try playing around with the timing and speed to get different effects
• Depending on how loose the threads are, you may need to pre-wind the threads around the axle by using the A button before triggering the TentacleAction function

Step 23: Put the Body On

• Put the body on
  • The thread should slide into the thin cutouts in the body
  • The servo wire should go through the larger cutout
• Optional: You can add a bit of glue to secure the body to the cardboard base (I didn't in case I wanted to access the inside)

Step 24: Give It a Face

• Give your Octobot a face!
• Touch the logo and shout "BOO!" to make Octobot retract its tentacles!