DIY plastic shredder with gears and safety

Scratch-Fabricated Plastic Gobbling Shredder Brings Recycling Home

June 1, 2016 by 10 Comments

[Jason Knight], an intern at FabLab RUC, has worked hard for 9 months to make a sheet plastics shredder for HDPE and LDPE from things like plastic bags, bubble wrap and air cushion packaging with the goal of recycling the shredded plastic. Why shred these things? When broken down to smaller pieces they can be melted in a consumer grade oven (like where you cook your frozen pizzas) then molded into new objects or extruded into 3D printing filament.

We especially like his big homemade 1.1 inch (30mm) thick wooden gears, for transferring the rotation from the motor to the cutting shafts while giving a step up in torque. As you can see in the video below, the gears definitely add an extra look of power to the machine.

The blades are the shape you most often see in shredders, gear-like disks side-by-side with teeth cut from them that pull the plastic in while shredding it (in contrast to this lower-throughput experimental DIY shredder made with two steel pipes). [Jason’s] multiple teeth are a bit of work to fabricate — not only were all the teeth milled from sheet metal but they then had to be individually sanded to remove burrs from the edges. It was worth it, as this has no problem chewing waste plastics to pieces.

Shredders can be dangerous machines for wandering fingers so [Jason] added a few safety features. Those include a drawer that you open to insert your plastic into the shredding area and a guard that completely surrounds the gears. And both features include transparent plastic areas so that you can still watch the impressive working parts in action.

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Transistor Logic Clock Has 777 Transistors

June 1, 2016 by 23 Comments

Sometimes, the parts list says it all. 777 transistors, 1223 resistors, 136 LEDs, 455 crimp connectors, 41 protoboards and 500 grams of solder. That’s what went into this transistor logic clock build.

While additional diodes and capacitors were tolerated in this project, a consequent implementation of a discrete transistor logic clock, of course, does not contain a quarz oscillator. Instead, it extracts its clock signal from the mains frequency in its power supply. Because mains frequency is slow, it can be stepped down to a clock-applicable 1 Hz by a simple counter unit which already spreads its discrete transistors across 4 protoboards.

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Hackaday Prize Entry: Ears On The Back Of Your Head

May 31, 2016 by 11 Comments

From context clues, we can tell that [TVMiller] has been in and around NYC for some time now. He has observed a crucial weakness in the common metropolitan. Namely, they deafen themselves with earphones, leaving them senseless in a hostile environment.

To fix this problem, he came up with a simple hack, the metrophone. An ultrasonic sensor is hung from a backpack. The user’s noise making device of choice is plugged into one end, and the transducer into the other. When the metropolitan is approached from the rear by a stalking tiger or taxi cab, the metrophone will reduce the volume and allow the user to hear and respond to their impending doom. Augmentation successful.

The device itself consists of an off-the-shelf ultrasonic sensor, an Arduino, and a digital potentiometer. It all fits in a custom 3D printed enclosure and runs of two rechargeable coin cells. A simple bit of code scales the volume to the current distance being measured by the ultrasonic sensor once a threshold has been met.

In the video after the break, you can observe [TVMiller]’s recommended method for tranquilizing and equipping a metropolitan in its natural habitat without disturbing its patterns or stressing it unduly.

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Fixing The Terrible Range Of Your Cheap NRF24L01+ PA/LNA Module

May 31, 2016 by 66 Comments

nRF24L01+ PA/LNA module specs look great on paper. Wireless communication up to 1000m in a small package readily available from a variety of cheap sources in China? The hard work of software connectivity already done by a variety of open source projects? Sounds great! But if you mashed BUY and are getting maybe 1% of that range, don’t worry because thanks to these clear directions, they can be fixed.

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Exoskeleton Boots Put A Spring In Your Step

May 31, 2016 by 16 Comments

Human ancestors have been walking around on two legs for a few million years. We’d imagine that by now we’ve figured out a pretty efficient mechanism for getting around. Unconvinced, however, researchers at Carnegie Mellon University have developed an “exo”-boot that reduces the metabolic rate of walking by seven percent. Best of all, the mechanism requires no additional source of active power input besides the human legs that are wearing them.

Upon close inspection, the boots reduce the overall applied torque at the angle joint at a critical point where the heel begins to lift off the ground. Energy in, energy out. The spring ratchets to a loaded position as the user plants their foot. This ratchet releases, re-engaging the stored spring force as the user brings their heel back off the ground. A seven percent reduction in metabolic rate may not sound like much, but, according to the paper, it’s the equivalent of about four kilograms less weight in your backpack on that next hiking trip.

As for what specific costs are being reduced to lower the body’s metabolic rate, the researchers still aren’t completely sure. An off-the-cuff look at the joints and moments from a mechanics perspective won’t give us a sure-fire answer since the energy consumption processes of muscles are, well, complicated. In fact, by varying spring stiffness in their design, they discovered that springs that were either too stiff or too loose had no effect on the metabolic rate. Yes, they’ve certainly stumbled on a sweet spot in terms of well-mixed circumstances, but the answer behind why the new robot-legs work so smoothly will be a study for the future.

If you haven’t jumped into the world of exo-skeleton building, let [James Hobson] be your guide into pushing our bounds with homebrew mechanical advantages. Now let’s keep our fingers crossed for some long-fall boots.

via [The Washington Post]

Leg Mounted Beer Bottles For Underwater Propulsion

May 31, 2016 by 35 Comments

Sitting on the beach, finishing off a beer one day, [Rulof] realized that if he put a motor in the beer bottle with a propeller at the bottle’s mouth, he could attach the result to his leg and use it to propel himself through the water. Even without the added bonus of the beautiful Mediterranean waters through which he propels himself, this is one hack we all wish we’d thought of.

These particular beer bottles were aluminum, making cutting them open to put the motor inside easy to do using his angle grinder. And [Rulof] made good use of that grinder because not only did he use it to round out parts of the motor mounting bracket and to cut a piston housing, he also used the grinder to cut up some old sneakers on which he mounted the bottles.

You might wonder where the pistons come into play. He didn’t actually use the whole pistons but just a part of their housing and the shaft that extends out of them. That’s because where the shaft emerges from the housing has a water tight seal. And as you can see from the video below, the seal works well in the shallow waters in which he swims.

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Exquisite LED Handbag In The Wild

May 31, 2016 by 19 Comments

There is a lot of spectacle on display at Maker Faire. But to be honest, what I love seeing the most are well-executed builds pulled off by passionate hackers. Such is the case with [Debra Ansell]. She wasn’t exhibiting, just taking in all the sights like I was. But her bag was much better than my drab grey camera-equipment filled backpack; she build a handbag with an LED matrix and did it so well you will scratch your head trying to figure out if she bought it that way or not.

Gerrit and I walked right up and asked if she’d show it to us. We weren’t the only ones either. [Debra’s] bag started drawing a crowd as she pulled out her cellphone and sent “Hackaday” to the 10×15 matrix over Bluetooth. Check out our video interview below.

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