Simple Wi-Fi Cat Door Solves The Extra Critter Problem, And Nothing More

Anyone with an outdoor cat in their life knows their propensity for bringing home offerings, in the form of critters in various stages of the process of becoming ex-critters. And anyone with a hacker in their life knows that there’s a tendency to throw technology at this problem. But sometimes, the simplest solutions are the best.

Take this simple stepper-powered cat door lock. For [Jason Winfield], the essential problem with his outdoor cat’s late-night demands for reentry was having to manually unlock the cat door after a quick visual check that no midnight snacks were along for the ride. Such activity tends to make it hard to get back to sleep. One natural reaction to this would be to completely automate the process with machine learning to recognize the offering and deny entry; we’ve seen exactly that before, after all. But recognizing that the disruptive part was the getting up to check bit, [Jason] just whipped up a simple stepper-driven lock with an ESP8266 microcontroller. With a 3D-printed case and a battery pack, and a nearby Wi-Fi camera, the lock denies entry to the cat until he gets a look at it, at which point he simply hits the lock’s webpage to unlock the door. The video below would show the lock in action, except the cat buggered off once it got a whiff of the doings. Cat’s gonna cat.

What we appreciate about this project is its simplicity. It solves the problem with the minimum feature set, which is something we see too little of sometimes. It’s also got some nice ideas, like the non-captive bolt that can be removed to unlock the door if the battery dies. Smart thinking, [Jason], and sweet dreams.

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I’ll See Your Seven-Segment Mechanical Display And Raise You To 16 Segments

Mechanical multi-segment displays have become quite a thing lately, and we couldn’t be more pleased about it. The degree of mechanical ingenuity needed to make these things not only work but look good while doing it never ceases to amaze us, especially as the number of segments increases. So we submit this over-the-top 16-segment mechanical display (Nitter) for your approval.

The original tweet by [Kango Suzuki] doesn’t have a lot of detail, especially if you can’t read Japanese, but we did a little digging and found the video shown below. It shows a lot more detail on how this mechanism works, as well as some of the challenges that cropped up while developing it. Everything is 3D printed, and flipping the state of each of the 16 segments is accomplished with a rack-and-pinion mechanism, with the pinions printed right into each two-sided cylindrical segment. The racks are connected to pushrods that hit a punch card inserted into a slot in the rear of the display. The card has holes corresponding to the pattern to be displayed; when it’s pushed home, the card activates a mechanism that slides all the racks that line up with holes and flips their segments.

This isn’t the first multi-segment mechanical masterpiece from [Kango Suzuki] that we’ve featured, of course. This wooden seven-segment display works with cams rather than punch cards, but you can clearly see the hoe the earlier mechanism developed into the current work. Both are great, and we’re looking forward to the next segment count escalation in the mechanical display wars.

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A Linear Stencil Clock Built For Quiet Operation

We around the Hackaday shop never get tired of seeing new ways to mark the passage of time. Hackers come up with all manner of interesting timekeeping modalities using every imaginable material and method of moving the mechanism once per whatever minimum time unit the hacker chooses to mark.

But honestly, there are only so many ways to make a clock, and while we’re bound to see some repeats, it’s still nice to go over old ground with a fresh approach. Take this linear sliding stencil clock for instance. [Luuk Esselbrugge] has included some cool design elements that bear a closer look. The video below shows that the display is made up of four separate stepper motors, each driving a vertical stencil via a rack-and-pinion mechanism. There a simple microswitch for homing the display, and a Neopixel for lighting things up.

The video below shows that the stencils move very, very slowly; [Luuk] says that this is to keep the steppers as quiet as possible. Still, this means that some time changes take more than a minute to accomplish, which is a minor problem. The Neopixel also doesn’t quite light up just one digit, which should be a pretty easy fix for version 2. Still, even with these issues, we like the stately movements of this clock, and appreciate [Luuk]’s attempts to make it easier to live with.

Don’t let the number of clocks you see on these pages dissuade you from trying something new, or from putting your twist on an old design. Start with fridge magnets, an old oscilloscope, or even a bevy of steel balls, and let your imagination run wild. Just make sure to tell us all about it when you’re done.

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MIDI Slide Whistle Shows The Value Of A Proper Fipple

We pride ourselves on knowing the proper terms for everyday things: aglet, glabella, borborygmi, ampersands. But we have to confess to never having heard of a “fipple” before finding this interesting MIDI-controlled slide whistle, where we learned that the mouthpiece of a penny whistle or a recorder is known as a fipple. The more you know.

This lesson comes to us by way of a Twitter post by [The Mixed SIgnal], which showed off the finished mechanism in a short video and not much else. We couldn’t leave that alone, so we reached out for more information and were happy to find that [The Mixed SIgnal] quickly posted a build log on Hackaday.io as well as the build video below.

The slide whistle is a homebrew version of the kind we’ve all probably annoyed our parents with at one time or another, with a 3D-printed fipple (!) and piston, both of which go into a PVC tube. Air is supplied to the pipe with a small centrifugal blower, while a 3D-printed rack and pinion gear of unusual proportions moves the piston back and forth. An Arduino Due with a CNC shield controls the single stepper motor. The crude glissandos of this primitive wind instrument honestly are a little on the quiet side, especially given the racket the stepper and rack and pinion make when queuing up a new note. Perhaps it needs more fipple.

While the humble author is new to fipple-isms, luckily the Hackaday editors see all and know that there two epic hacks featuring fipples to create bottle organs. These are far from the first weirdest instruments we’ve seen — a modulin, a Wubatron, and the Drum-Typeulator all fit that bill well. But we like what [The Mixed Signal] has done here, and we’re looking forward to more.

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Self-Playing Kalimba V2 Thanks To Readers Like You

Would you like to know the great thing about this community we have here? All the spitballing that goes on every day in the comments, the IO chat rooms, and in the discussion threads of thousands of projects. One of our favorite things about the Hackaday universe is that we help each other out, and because of that, our collective curiosity pushes so many designs forward.

[Gurpreet] knows what we’re talking about. He’s back with version two of his self-playing kalimba, driven as strongly as ever by the dulcet tones of the Avatar theme. Now the robo-kalimba is rocking two full octaves, and thanks to your comments and suggestions, has relocated the servos where they can’t be picked up by the soundboard.

We gasped when we saw the new mechanism — a total of 15 rack and pinion linear actuators that make the kalimba look like a tiny mechanical pipe organ. Now the servos float, fixed into a three-part frame that straddles the sound box. [Gurpreet] melted servo horns to down to their hubs rather than trying to print something that fits the servos’ sockets.

Thumb your way past the break to check out the build video. [Gurpreet] doesn’t shy away from showing what went wrong and how he fixed it, or from sharing the 3D printering sanity checks along the way that kept him going.

Plucking kalimba tines is a difficult problem to solve because they’re stiff, but with timbre sensitive to many degrees of pressure. A slightly easier alternative? Make a toy player piano.

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A Word Clock, The Hard Way

We’ve all seen word clocks, and they’re great, but there are only so many ways to show the time in words. This word clock with 114 servos is the hard way to do it.

We’re not sure what [Moritz v. Sivers] was aiming for with this projection clock, but he certainly got it right. The basic idea is to project the characters needed to compose the time messages onto a translucent PVC screen, which could certainly have been accomplished with just a simple character mask and some LEDs. But for extra effect, [Moritz] mounted each character to a letterbox mounted over a Neopixel. The letterboxes are attached to a rack and pinion driven by a micro servo. The closer they get to the screen, the sharper the focus and the smaller the size of the character. Add in a little color changing and the time appears to float out from a jumbled, unfocused background. It’s quite eye-catching, and worth the 200+ hours of printing time it took to make all the parts. Complete build instructions are available, and a demo video is after the break.

We like pretty much any word clock – big, small, or even widescreen. This one really pushes all our buttons, though.

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Save A Few Steps On Your Next Build With These Easy Linear Actuators

A lot of projects require linear motion, but not all of them require high-accuracy linear slides and expensive ball screws. When just a little shove for a door or the ability to pop something up out of an enclosure is all you need, finding just the right actuator can be a chore.

Unless someone has done the work for you, of course. That’s what [Ali] from PotentPrintables did with these 3D-printed linear actuators. It’s a simple rack-and-pinion design that’s suitable for light loads and comes in two sizes, supporting both the 9-g micro servos and the larger, more powerful version. Each design has a pinion that has to be glued to a servo horn, and a selection of rack lengths to suit your needs. The printed parts are nothing fancy, but seem to have material in the right places to bear the loads these actuators will encounter. [Ali] has included parts lists and build instructions in with the STL files, as well as sample Arduino code to get you started. The video below shows the actuators in action.

We’re heartened to learn that [Ali] was at least partly inspired to undertake this design by a previous Hackaday post. And we’re glad he decided to share his version; it might save us a few steps on our next build.

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