Gravity Defying Drips of a Bike Pump Controlled Fountain

People love to see a trick that fools their senses. This truism was in play at the Crash Space booth this weekend as [Steve Goldstein] and [Kevin Jordan] showed off a drip fountain controlled by a bike pump.

These optical illusion drip fountains use strobing light to seemingly freeze dripping water in mid-air. We’ve seen this before several times (the work of Hackaday alum [Mathieu Stephan] comes to mind) but never with a user input quite as delightful as a bike pump. It’s connected to an air pressure sensor that is monitored by the Arduino that strobes the lights. As someone works the pump, the falling droplets appear to slow, stop, and then begin flowing against gravity.

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All Your Displays Are Belong to Us

Artist and Hackaday reader [Blair Neal] wrote in with his incredible compendium of “alternative” displays. (Here as PDF.) From Pepper’s Ghost to POV, he’s got it all covered, with emphasis on their uses in art.

There’s an especially large focus on 3D displays. Projecting onto screens, droplets of water, spinning objects, and even plasma combustion are covered. But so are the funny physical displays: flip-dots, pin-cushions, and even servo-driven “pixels”.

Flavien Théry’s La Porte 
Flavien Théry’s La Porte

We really liked the section on LCDs with modified polarization layers — we’ve seen some cool hacks using that gimmick, but the art pieces he dredged up look even better. Makes us want to take a second look at that busted LCD screen in the basement.

We’re big fans of the bright and blinky, so it’s no surprise that [Blair] got a bunch of his examples from these very pages. And we’ve covered [Blair]’s work as well: both his Wobbulator and his “Color a Sound” projects. Hackaday: your one-stop-shop for freaky pixels.

[Blair]’s list looks pretty complete to us, but there’s always more out there. What oddball displays are missing? What’s the strangest or coolest display you’ve ever seen?

Making the Dune “Pain Box” a Reality

If you are unfamiliar with Dune, then you may not know what the pain box is. The pain box is a fictional device that produces an excruciating burning sensation without causing any actual damage. [Bryan] has been working on a project to duplicate this effect in the real world. It sounds like he may be on the right path by using the “thermal grill illusion”.

The thermal grill illusion is a sensory trick originally demonstrated back in 1896. The trick is made up of two interlaced grills. One is cool to the touch, and the other is warm. If the user touches a single grill, they won’t experience any pain because neither temperature is very extreme. However if the user places their hand over the interlaced grills simultaneously they will immediately experience a burning heat. This usually causes the person to pull their hand away immediately. It’s a fun trick and you can sometimes see examples of it at science museums.

The thermal grill illusion sounded like the perfect way to make the pain box a reality. [Bryan] has set specific constraints on this build to make it more true to the Dune series. He wants to ensure the entire package fits into a small box, just big enough to place an adult hand inside. He also wants to keep safety in mind, since it has the potential to actually cause harm if it were to overheat.

[Bryan] has so far tried two methods with varying success. The first attempt involved using several thermoelectric coolers (TECs). [Bryan] had seen PCBs etched a certain way allowing them to radiate heat. We’ve seen this before in 3D printer surfaces. He figured if they could become hot, then why couldn’t they become cold too? His idea was very simple. He etched a PCB that had just two large copper pours. Each one branched out into “fingers” making up the grill.

Each side of the grill ultimately lead to a flat surface to which a TEC was mounted. One side was cold and the other was hot. Heat sinks we attached to the open side of the TECs to help with performance. Unfortunately this design didn’t work. The temperature was not conducted down to the fingers at all. The back side of the PCB did get hot and cold directly under the TECs, but that wouldn’t work for this illusion.

The latest version of the project scraps the PCB idea and uses small diameter copper tubing for the grill. [Bryan] is working with two closed loop water systems. One is for warm water and the other is for cold. He’s using an aquarium pump to circulate the water and the TECs to actually heat or cool the water. The idea is that the water will change the temperature of the copper tubing as it flows through.

While the results so far are better than the previous revision, unfortunately this version is having problems of its own. The hot water eventually gets too hot, and it takes over an hour for it to heat up in the first place. On top of that, the cold water never quite gets cold enough. Despite these problems, [Bryan] is hopefully he can get this concept working. He has several ideas for improvements listed on his blog. Maybe some Hackaday readers can come up with some clever solutions to help this project come to fruition.

Camera trick lets you see sound waves in falling water

From this still image you’d think the hose dispensing the water is being moved back and forth. But watch the video after the break and you’ll see the hose is quite steady, as is the standing wave of water. It’s bizarre to be sure. Knowing how it works makes cognitive sense, but doesn’t really diminish the novelty of the demonstration.

This is the second time [Brasspup] has posted a video of this phenomenon. The newest version does a great job of showing several different patterns. But even the first segment from a year ago, which has over 4 million hits, shows the water moving against gravity. We also saw a similar rig in a links post a year ago.

We’d call it an optical illusion but it’s really more of a technological illusion. The water is falling past a sub-woofer speaker which is tuned to 24 Hz. At the same time, the camera filming the demonstration is capturing 24 frames per second. As was mentioned then, it’s much like flashing a light to freeze the water in mid-air. But the flashing of the frames is what causes this effect.

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Build a real-life Escher’s Waterfall

Instructables user [GuokrDIY] has provided a translation of a detailed guide on making one of our favorite Escher inspired illusions. Unlike the previous speculated solutions to Escher’s waterfall this one manages to keep the water path coherent up until the top level. The trick of the whole setup is very carefully controlling perspective to overlap the water source and outlet.  We say water but for some reason the builder is actually using “toilet detergents” as the liquid… At any rate, the liquid is allowed to flow downhill until it reaches the fourth corner, which does not exist. The liquid actually falls off the end of the table (out of sight) and into a basin. A carefully timed pump in the basin pushes liquid up to the top of the waterfall through one of the model’s pillars, where it then cascades over the wheel.

Using sketchup to model the various structural components of the waterfall the design is fashioned out of PVC and ABS plastic, then skinned with mapped textures to ensure that everything looks coherent. The visual details are fine tuned by viewing the whole setup through a camcorder.  The hardest part of the illusion seems to be modulating power to the pump in order to time it with the liquid’s flow.

We just hope that thing about toilet detergent was a mistranslation or some kind of sarcasm from the original Chinese article.  Check out the model in action after the jump!

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How Escher’s impossible waterfall was faked

Study the image above closely. You’ll notice that physically it is an impossible object, yet this is a screenshot of full-motion video. The clip after the break shows a gentleman pouring water into the waterfall where the wheel is located. The liquid flows in a direction that appears to be uphill, then falls onto the waterwheel where it was originally poured. Ladies and Gentleman, we have the solution to the world’s energy crisis. Nope, we have a hoax and the real question is how was it done?

[David Goldman] has come up with quite the explanation. He watched the video very closely and the put together a three-dimensional diagram showing how he would build the apparatus. If you saw the movie Inception (we highly recommend you do) you will remember the infinite stair puzzle that is exposed as an optical illusion. [David’s] proposed method for debunking this hoax uses a similar build that comes in four different, precisely placed elements.

We’ve got to hand it to him. That’s a brilliant theory! Of course the first commenter on the post linked above calls this out as CGI and we’re inclined to go with that answer but that’s much less fun.

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