Introduction: How to Make Your Smart Mjolnir ?

About: Web raider since 1995. Blogger on and tweeter with @cyroultwit

A client of Curiouser (my company) ask me to make an original attraction for the French salon Geekopolis. I had to try to build a "wearable computing" thing for geeks... And I only had at this time a little Flora (a Arduino board like for Wearable), 4 leds and, an accelometer an only 5 nights free to build this… l love this sort of challenge

So, after many crappy ideas (data gloves, magic baguette, etc.), I choose to build a Smart Thor Hammer (Mjolnir) which could change his color when you shake it. The challenge : succeding in flasing the leds in blue color.

Because you don’t know, young uncultured people raised with mass appeal Marvel movies, that old norwish Mjöllnir (pronounce… I don’t know in English) means lightning. And I always prefer the lightning in blue on the comics.

The idea was here. But the principal issue of this project was the hammer solidity. Indeed, this object was intended to suffer from hard handling from clumsy cosplayers for the 2 days of the salon.

So here is the making of Mjolnir. A very exciting project (you can find the french Mjolnir tutorial here).


  • 4 Neopixels
  • 1 Flora (from Adafruit)
  • 1 Flora accelerometer
  • 1 pickaxe handle
  • 1 spray of foam rubber
  • 1 spray of stone / metal paint
  • 1 pot of white glue
  • A little of varnish, a plastic cap, a knife, a cutter, superglue, …
  • 1 long screw and 2 nuts
  • 2 leather straps, some thumbtacks
  • 5 nights

Step 1: The Beginning of Mjolnir

Like a Dvergr (dvarf) of Svartalfheim, my first step was to build the hammer himself. It was impossible to redo the same Thor's Hammer, with its representative handle. This little handle came from a joke from Loki to the dwarf who was forging Mjolnir. But I needed a bigger handle to attract the crowd (hum, that’s what she never said).

So I noticed 2 foam rubber packs for wrapping a PC. I cut the corners to fake some old bevel’s stroke on a stone’s block.

After gluing the packs I needed to reinforce them (and give them some weight). For this, the expansive foam rubber is great. It glue everything (equally your fingers) and fill the space perfectly.

After, you have to cut all the bits that go out of the object. It’s not perfect, but it begins to look like something.

Step 2: Mjolnir Is Not Metal Nor Stone, Mjolnir Is Metal-stone

But I had a problem : how suppressing the holey, spongy aspect of the foam pack ?

The answer came from this tuto from Hackday where Caleb Kraft use white glue to harden the foam.

I used this genius idea before painting the object with a paint spray metal/stone.

Step 3: The Big Handle of Mjolnir

To build it, I cut a pickaxe handle (9€) at the good length.

I engraved some celtic’s interlaces at the end. Il know that Celtic is not Nordic, but when I engrave celtic interlaces with my knife during the pale night, I feel like another man.

After the engraving, it’s time for the varnishing to give the hard gleaming aspect which make a big part of the hammer’s success with ladies and some cosplayer’s guys.

I also make a hole on the handle to get over a wrist-strap. In French wrist strap is translated by “dragonne” (the lady of the dragon). I prefer this term, because it’s cool to have a dragonne for Mjolnir, isn't it ?

Step 4: Final Assembly

The final step consisted in coming through the hammer to fix the handle. I added a security screw (through the hammer and the handle), with 2 bolts at the ends, to be sure to fix all of it.

I also add a plastic cap of a coffee box to give the look of Mjolnir on the Kirby’s comics. And I finished by surrounding the handle with a little leather strap, studding this with thumbtacks, and added the dragonne.

Step 5: The Electronic Step

Flora is a little Arduino board very simple to program. I only have to branch the leds (Neopixels), the accelerometer, test the connections, write the program (you can download the code enclosed: accelerometre_base.ino). And after testing, the weld.

This step took me less than 2 hours. And it would take me less time if I had not weld a wire in the wrong side.

I let the « electronic side » of the hammer exposed to demonstrate the power of the wearable techs. And go to the salon !

Step 6: Mjolnir in Live

In the Geekopolis salon, the hammer was a big success for young and old children. Some strong guys try to shake Mjolnir to the dead. But they didn’t succeed.

The hammer held on during two days. And I can say I have now my Dvergr diploma.