In comic books and blockbusters, only the worthy can lift Thor’s hammer. But you don’t have to be a hero to wield Allen Pan’s version of Mjolnir. While watching last year’s Avengers: Age of Ultron, the freelance engineer noticed “a flippant remark about the handle being ‘imprinted,'” Pan says. The idea that fingerprints could unlock the hammer inspired him.
“I thought about how someone might go about replicating that function, and there it was,” he says. All he needed was an electromagnet—which can be turned on and off by electrical current—and a fingerprint scanner. Pan wired together the electromagnet and scanner, and placed them inside an off-the- shelf toy Mjolnir. When switched on, his hammer becomes magnetized and will stick fast to metal until the scanner recognizes his touch and releases the weapon.
Last October, Pan used his gizmo to prank unsuspecting Angelenos: He placed the hammer on metal surfaces, such as manhole covers, and recorded passersby as they futilely tried to lift it. Then he would walk into frame and effortlessly heft it himself. His online video has been viewed more than 14 million times. The Popular Science team tested out our own version—with limited success—in the video below. But don’t settle for watching. Follow these instructions to build your own Mjolnir and try it yourself.
- Time: 8 hours
- Cost: $250
- Difficulty: Hard
- X-Acto knife
- Hot-glue gun
- Soldering iron
- Plastic toy version of Thor’s hammer, Mjolnir
- 10-by-3⁄4-inch threaded black pipe with cap and flange
- Suede strip
- Fingerprint scanner and cable
- Clear fingernail polish
- Toggle switch
- 9-volt battery and case
- 3⁄4-inch plywood base
- Drawer handles
- Microwave transformer
- Crimp-on ring tongue terminals for 18-to-22-gauge wire
- Drywall screws
- Momentary capacitive touch sensor
- Four 12-volt lead-acid batteries
- Arduino Uno
- 60-volt solid-state relay
- Crimp-on 1⁄4-inch quick disconnects for 18-to-22-gauge wire
- Velcro and plywood strips
- Unscrew the prop’s handle and trim down the screw threads. Cut out a removable door on the top of the hammer and cut three more rectangular sections on the bottom.
- To make a new handle from pipe, first use a Dremel to cut a hole for the fingerprint scanner. Attach the pipe flange. Wrap the full length of the pipe in the suede leather, stuck in place with hot glue. Fill in any gaps with suede cutoffs.
- Cover the metal section of the fingerprint scanner in two coats of clear nail polish to prevent it from grounding to the pipe. Hot-glue the scanner into the pipe so that the connector points downward and attach the cable. Glue the toggle switch to the opposite end of the pipe, running the wires past the fingerprint scanner and into the 9-volt battery case.
- Cut off the top section of your microwave transformer using a dremel and remove the primary coil which has thicker wire. Also remove any connecting wires, saving only the secondary coil which contains several loops of very fine wire. Replace the secondary coil and solder wire to each end of the coil. Bracket the transformer with the drawer handles and attach them to the plywood base. Screw the pipe assembly to the opposite side of the base, keeping the wires outside of the pipe flange. Place the entire assembly inside of the plastic Mjolnir, with the transformer sticking out of the holes in the bottom.
- Connect the capacitive sensor to the pipe flange with screws, washers, and crimp connectors. Slide the four 12-volt batteries into the case.
6.Use the wiring diagram above to wire together the Arduino, the capacitive touch sensor, the fingerprint scanner, the relay, the transformer, and the batteries into a circuit. Upload this fingerprint code to the Arduino to teach the hammer your fingerprint. Reminder: Opening the serial monitor resets the Arduino, but resetting the Arduino does not reset the fingerprint scanner. Finally, upload this code to run the hammer.
7.Place the hammer on a metal surface, such as a manhole cover, and flip on the switch in the handle. When someone grabs the handle near the base, triggering the capacitive sensor, the electromagnet will activate, gluing the hammer to the metal. To release Mjolnir, press your finger against the fingerprint scanner while grabbing the handle.
This article was originally published in the July/August 2016 issue of Popular Science, under the title “Only You Can Lift This Hammer.”