Introduction: Interactive Thor's Hammer (Mjolnir)

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While its not the electromagnetic kind of hammer, this one still has plenty of personality. There are three ways to activate it - when you hit things (flashes white), when you trigger it with a remote button (bifrost), and when you get too far away from Mjolnir (angry red).

Since I plan on taking this to conventions, I realize people may want a picture with the hammer glowing. I put a three way switch in the bottom of the handle that allows you to toggle between "Always On" for pictures, "Off" which puts the Arduino to sleep to conserve battery, and "Sensor" mode that responds as listed above.

Step 1: Materials

Electronics

  • Arduino Uno
  • Arduino Fio
  • (2) XBees (Mine are Series 1)
  • XBee Shield
  • (2) Adafruit NeoPixel 8 x 8 Matrix
  • Fast Vibration Sensor Switch

Hammer

  • (2) Acrylic Sheets cut to 5" x 8"
  • Vellum (if you can get the large drafting rolls, that's why I ended up using)
  • Balsa wood
  • Black paper (cardstock or posterboard works best)
  • Luan Plywood (I had this lying around, foam board would probably work too)
    • (2) 5" x 8"
    • (2) 5" x 5"
    • (2) 4" x 4"
  • 1" PVC Pipe (Big box hardware stores sell 1" x 2' cuts)
  • 1" Female Adapter
  • 1" Hex Plug
  • 1-1/4" Cap
  • Leather strip
  • Foam Board
  • Silver Paint

Tools

  • X-acto Knife
  • Extra blades
  • Glass Cutter
  • ** Razor saw
  • Paint sprayer
  • Weldbond Contact Cement (The small 3 oz bottle goes a LONG WAY)
  • Soldering Iron
  • Solder
  • Hot Glue

** is a nice to have tool

Step 2: Hammer Construction: Basic Design

The idea behind the way the hammer fits together is the ability to take it apart easily for fixing anything that might go wrong while out at a convention or changing out batteries.

The handle, base, and end-caps are all one piece. The acrylic sides and top are separate and can be lifted up. The acrylic sides "lock in" to little slots on the base. The top is screwed in to the handle at the very top.

The NeoPixel Matrices are attached to the handle inside the hammer head. The arduino board and battery are attached to the base. An on-off-on rocker switch is at the bottom of the handle where the leather loop will be.

When I took my last project (Animatronic Hocus Pocus book) out to conventions, I got a lot of requests to leave the eye open. My program didn't allow this, so I wanted to account for that with this project. The rocker switch will have two separate on modes - Lights On and Sensors On. Lights On will turn the NeoPixel Matrices on without any fancy programming. Sensors On will wait until one of three sensor inputs are activated (Muscle, vibration, or proximity). Off will help me save battery power! It's never fun to have an awesome prop that has run out of power.

Step 3: Hammer Construction: Bottom Piece

Bottom Piece

  • Cut a hole in the center of both 5 X 8 pieces of board. The hole should be large enough to fit the pvc pipe easily
  • Attach the female adapter to the top of the PVC pipe
  • Stick the PVC pipe with the female adapter through one of the 5 x 8 board
    • Placing the other board on top of the female adapter, you want the distance from the bottom board outer edge to the top board outer edge to be 5" (the height of the acrylic)
    • Attach with hot glue
  • Cover the bottom board with a layer of the black paper and then the vellum
  • Cut a whole in one of the frosting covers
  • Cover the frosting cover in black paper and then vellum
  • Cut pieces of balsa wood to fit the center sides of the 5 x 8 board
  • Glue a 2-3 pieces of the 4 x 4 foam board to the center of the 5 x 5 board. Repeat with the other side
  • Cover the stacks with black paper creating the end cap sheet, then cover with a layer of vellum
  • Hot glue these end pieces to the bottom board

Step 4: Hammer Construction: Top Piece

  • Print two transparencies - one for each acrylic side
  • Spray the acrylic sheet with spray glue and attach the transparency. One to each side.
  • Cover any clear pieces of acrylic with black paper
    • Hot glue the acrylic sides to the remaining 5 x 8 board
  • Tip: Find a box approximate 5 inches wide and rubber band the top piece to it while it cures
  • Cover the top 5 x 8 board with black paper
  • Cover the entire top piece in vellum in one piece
  • Glue the Hex Plug to the frosting cover
  • Cover the frosting cover with black paper and then vellum
  • Cover the end cap with black paper and then vellum
  • Airbrush the entire hammer (including end cap) silver, and then "age" with a dark smoke color and dry-brushing

Step 5: Hammer Construction: Handle

  • Drill a hole near the bottom of the handle
  • Cut a strip of leather and feed it through the hole (this becomes your wrist strp)
  • Cut strips of leather and wrap them around the length of the pvc
    • This took a bit of figuring out, there's probably tutorials on here somewhere to help out

Step 6: Electronics: Wiring

I soldered everything I could on to an arduino shield. It's not the prettiest thing, but it works.

  • Vibration sensor: Pin 7
  • Three Way Switch: Digital Pin 2, Digital Pin 3
  • Lightning NeoPixel Panel: Pin 6
  • Thor NeoPixel Panel: Pin 9

Step 7: Electronics: Coding

The code is sort of long and in two parts. Mjolnir is for the hammer itself, and the Arduino Fio "Bracer". Now the way I determine if Mjolnir is too far away from the Bracer is not exact at all, but it serves the purposes of a costume.

https://github.com/ImagineersApprentice/Mjolnir