Several people at a museum exhibit about magnetism

Hands-On Museum Exhibit Brings Electromagnetism To Life

Magnets, how do they work? Although the quantum mechanics behind ferromagnetism are by no means easy, a few simple experiments can give you a good grasp of how magnets attract and repel each other, and show how they interact with electric phenomena. [Niklas Roy] built an exhibit for the Technorama science museum in Switzerland that packs a bunch of such electromagnetic experiments in a single package, appropriately called the Visitors Magnet.

The exhibit consists of a big magnet-shaped enclosure that contains a variety of demonstrators that are all powered by magnets. They range from simple compasses to clever magnetic devices we find in the world around us: flip-dot displays for instance, on which you can toggle the pixels by passing a magnet over them. You can even visualize magnetic field lines by using magnetic viewing film, or turn varying fields into audio through a modified telephone receiver.

Another classic demonstrator of electromagnetism is a color CRT monitor, which here displays a video feed coming from a camera hanging directly overhead. Passing a magnet along the screen makes all kind of hypnotizing patterns and colors, amplified even more by the video feedback loop. [Niklas] also modified the picture tube with an additional coil, connected to a hand-cranked generator: this allows visitors to rotate the image on the screen by generating an AC current, neatly demonstrating the interaction between electricity and magnetism.

The Visitors Magnet is a treasure trove of big and small experiments, which might not all withstand years of use by museum guests. But that’s fine — [Niklas] designed the exhibit to be easy to maintain and repair, and expects the museum to replace worn-out experiments now and then to keep the experience fresh. He knows a thing or two about designing engaging museum exhibits, with a portfolio that includes vector image generators, graffiti robots and a huge mechanical contraption that plays musical instruments.

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A diagram showing an LED on the left, a lever-style plumbing valve in the center, and an Arduino Uno on the right.

Plumbing Valves As Heavy Duty Analog Inputs

Input devices that can handle rough and tumble environments aren’t nearly as varied as their more fragile siblings. [Alastair Aitchison] has devised a brilliant way of detecting inputs from plumbing valves that opens up another option. (YouTube) [via Arduino Blog]

While [Aitchison] could’ve run the plumbing valves with water inside and detected flow, he decided the more elegant solution would be to use photosensors and an LED to simplify the system. This avoids the added cost of a pump and flow sensors as well as the questionable proposition of mixing electronics and water. By analyzing the change in light intensity as the valve closes or opens, you can take input for a range of values or set a threshold for an on/off condition.

[Aitchison] designed these for an escape room, but we can see them being great for museums, amusement parks, or even for (train) simulators. He says one of the main reasons he picked plumbing valves was for their aesthetics. Industrial switches and arcade buttons have their place, but certainly aren’t the best fit in some situations, especially if you’re going for a period feel. Plus, since the sensor itself doesn’t have any moving parts, these analog inputs will be easy to repair should anything happen to the valve itself.

If you’re looking for more unusual inputs, check out the winners of our Odd Inputs and Peculiar Peripherals contest or this typewriter that runs Linux.

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