4-Stroke Clock Fires On All Cylinders

February 11, 2018 by Kristina Panos 8 Comments

We love a good clock build around here, especially if it tells time in a unique way. This 4-stroke digital clock designed by [lagsilva] takes the checkered flag in that category. As it displays the time, it also demonstrates the operation of an internal combustion engine. The numbers take the form of pistons and dance an endless repetition of intake, compression, combustion, exhaust.

The clock’s digits are made from two LED matrices driven by an Arduino Uno and a couple of MAX7219 driver boards. The dots that form the digits move up and down the matrices in 1-3-4-2 firing order. As each piston-digit reaches top dead center, its number lights up. This makes it easy to see the firing order, even at higher RPM values.

Our favorite thing about this clock is the variable RPM setting. There’s a 10k pot around back that adjusts the speed of the pistons between 100 and 800 RPM, and it’s configured to accurately represent piston movement at each increment. Floor it past the break to watch the clock rev up and slow back down.

Although it’s difficult to read the time at 800 RPM, it’s awesome to see a real-time visualization of cylinder movement at the average idle speed of a passenger car. We think it might be neat to rev the engine another way, like with an arcade throttle lever or a foot pedal.

If you like the idea of a constantly-moving clock but prefer an analog readout, take a minute to look at this clock without a face.

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Ride Bike, Charge Phone

February 8, 2018 by Kristina Panos 49 Comments

Spring is coming to the northern hemisphere, and soon it’ll be nice enough outside to tool around town on your bicycle. But bikes don’t have power outlets, so phone charging on the go will require forethought and charged-up battery packs. It doesn’t have to be that way. You’re working to make the bike move, so why not make the bike work for you?

If you’ve ever used a motor as a generator, then you can see where this is going. That’s the underlying principle behind [Creativity Buzz]’s bike-powered phone charger. As the bike wheel turns, the rim comes in contact with a small wheel attached to the output shaft of a DC motor. Cranking the output shaft of a motor with permanent magnets inside will induce a small voltage, and here it is amplified with a DC-DC boost converter and output to a USB jack.

As long as you can find a way to secure the phone to the bike frame, or use a long cord and good cable management, you’re in business. Wheelie past the break to watch [Creativity Buzz] build it and give it a stationary test run. While you wait for bike-riding weather, you can still use this kind of charger by turning a crank.

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Build A Tiny Hot Wire Foam Cutter

February 8, 2018 by Kristina Panos 34 Comments

Let’s face it: cutting foam with a knife, even a serrated plastic knife meant for the job, is a messy pain in the ass. This is as true for insulation board as it is for the ubiquitous expanded polystyrene kind of foam used for everything from coffee cups to packaging material.

Those stick-type hot wire cutters from the craft store that plug into the wall aren’t much better than a knife. The actual cleaving of foam is easier, but dragging a long, hot flexible wand through rigid foam just right, without making burn marks, is pretty frustrating. It’s not like you can hold the other end to keep it steady. A foam cutter built like a coping saw but held parallel to the wire would offer much better control.

[Techgenie]’s handheld hot wire foam cutter is a simple build based on a single 18650 and a piece of nichrome wire. While this is probably not the most Earth-shattering hack you’ll see today, it’s a useful tool that can be made in minutes with items on hand. Laptop chargers are full of 18650s, and nichrome wire can be sourced from old toasters, hair dryers, or space heaters.

You shouldn’t use just any old wire for this, though, or the battery will get hot and potentially explode. Nichrome wire has a high resistance, and that’s exactly what you want in a tool that essentially shorts a battery to make heat. [Techgenie] used a momentary button instead of a switch, which is a good way to stay safe while using it. It wouldn’t hurt to add some protection circuitry and take the battery out when you’re done. Burn past the break to watch him build it and cut a few tight turns with ease.

If you have bigger, more complicated foam-cutting jobs in mind, why not build a CNC version out of e-waste?

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Cat Plays The Silver Ball For Treats

February 8, 2018 by Kristina Panos 12 Comments

It’s pretty easy to train a dog to do things for treats. They’re eager to please. But a cat? Most cats have better things to do than learn tricks no matter how many treats are involved. But if you make an autonomous game out of learning a trick, they just might go for it.

That’s the idea behind Touchy Fishy, a pinball machine for cats. It’s the newest iteration of treat-dispensing machines that [Kim] made for his cat, MIDI. The previous version was shaped like a dog’s head with a joystick for a nose. MIDI was so adept at pulling the joystick toward herself that [Kim] decided to try a new design using a lever.

Humans like challenges, too, and [Kim] wanted to make something purely mechanical this time around. The final product is mostly springs and laser-cut acrylic. MIDI pulls the spring-loaded lever downward, launching a pinball upward in an arc. At the top of its trajectory is a spinner enclosed in a circle. When the pinball hits the spinner, it sweeps a treat toward an opening, and the treat falls down where MIDI can eat it. The best part? The spinner also returns the captive pinball to its starting point, so MIDI can play until [Kim] gets tired of dropping treats into the hole. Watch MIDI claw her way to the high score after the break.

Most of the cat-related projects we’ve seen were built to keep hungry cats from sitting on their owner’s chests at 3AM, demanding to be fed. Here’s one that goes a step further by putting the cat to work collecting wiffle balls which it uses to pay for small amounts of kibble.

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Mae Jemison And The Final Frontier

February 6, 2018 by Kristina Panos 16 Comments

From the time Mae Jemison was a little girl, she was convinced that she would go to space. No one could tell her otherwise. She was sure that space travel would be as common as air travel by the time she was an adult. That prediction didn’t pan out, but that confidence combined with her intellect, curiosity, and the above-average encouragement of her parents drove Mae to do everything she wanted, including space travel.

Some people might become a doctor or a researcher, a dancer or an astronaut. But Mae became all of these things. Not everyone supported her non-traditional path—many people just pick a career and stick with it. Her path is impressive and through it all she gained a really interesting perspective on how education is approached, and what effects that approach has on society. After practicing medicine, joining a shuttle mission, appearing in Star Trek, and retiring from NASA, she became a voice for minority students and an advocate for integrating the arts and sciences in the standard curriculum.

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Repairs You Can Print: A Little Love For The Glove Box

February 5, 2018 by Kristina Panos 25 Comments

A few years ago, [Brieuc]’s car blew a fuse. He went to replace it, which unfortunately means removing the entire glove box. In his haste to get his baby back on the road, he accidentally broke one of the clips that holds the glove box on the dashboard.

[Brieuc] tried to just glue the thing back together, but it didn’t hold because the part has to flex a little bit for people who need to get into the fuse box. No one seems to offer a replacement for this small but vital hunk of plastic, though he did find someone offering total glove box replacements at highway robbery prices. Since there was still one good clip, he used it to design and print a strong ABS replacement.

This is a great example of the one-off utility of 3D printers. [Brieuc] didn’t need an exact copy, and since he was replacing an injection-molded part with additive manufacturing, he had the freedom to start with a bare-bones design, make adjustments as needed, and iterate until he got it right. It didn’t take long. The layer orientation of the first print made the legs too weak, but that’s a simple fix. The second version has lasted for three years and counting.

We get it. You don’t have the same car as [Brieuc], so this particular fix doesn’t sway you. But someday in the future when your zipper breaks or your dishwasher detergent cup won’t latch, 3D printing will be there to help.

Always Misplacing Your Keys? You Can Fix That With Some Logic Chips

February 4, 2018 by Kristina Panos 19 Comments

Every time he came home, it was the same thing. As soon as he crossed the threshold, his keys just disappeared. There was no other logical explanation for it. And whenever it was time to leave again, he had to turn the house upside down to find them.

One day, [out-of-the-box] decided he’d had enough and built a door-activated alarm system out of stuff he had on hand—a decade counter, a cheapo reed switch-based door alarm, and some transistors. When the door is closed, the decade counter’s output is set to light up a green LED. When he comes home and opens the door, the reed switch closes, triggering the decade counter to shift its output to the next pin. The red LED comes on, and NPN transistor grounds the piezo, sounding the alarm. The only way to stop it is by inserting a shorted 1/4″ phone plug conveniently attached to his key ring into a jack on the circuit board until he hears that satisfying click of safe key-ping.

For those times when immediately plugging the keys into the wall isn’t feasible, or if his keys should disappear before he has the chance, there’s a momentary on the board that will stop the symphony of robotic cicadas blasting out from the piezo. It’s also good for family members who don’t want to play along or haven’t yet earned their 1/4″ plug.

Be sure to check out the build video after the break, which is just through that door there. And keep an eye on your keys, eh? Hackaday is not responsible for lost or stolen personal articles. Should you lose them, we can only suggest making a new car key from the spare and printing replacements for any standard keys.

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