If you’re familiar with Marvel comics and Thor in particular then you’ll be aware that Mjolnir, Thor’s hammer, is pretty special because only the worthy can wield it. Thor was the one the hammer deemed worthy enough, but what’s a mere mortal like your or me to do? Well if you’re electrical engineer Allen Pan, you make your own, and you make sure that no one else but you can lift it, like Thor, without the superpowers.
Pan didn’t obtain superpowers overnight rather he came up with a seemingly simple solution to create his own “working” Thor hammer. He used strong magnets for this purpose and placed a microwave oven transformer electromagnet instead the hammer’s head.
The electromagnet uses electricity to produce a magnetic field strong enough to make it feel like the hammer can’t be lifted when it’s placed on a metal surface such as a manhole cover.
There’s a capacitive touch sensor on the hammer that’s hooked up to an Arduino Pro Mini and a solid state relay that works as a switching device. When someone grabs the handle the magnets switch on making it impossible for it to be lifted.
Pan can easily pick it up though because there’s a fingerprint sensor embedded in the handle that recognizes his thumbprint. He just needs to move his thumb over the sensor to switch off the magnets and pick up the hammer as if he is the only worthy being in the entire universe. It’s a neat little trick.