Author: Kristina Panos

1861 Articles

Dice Roller Keeps Germs Out Of Your Snake Eyes

October 5, 2020 by 5 Comments

Do you need a to find a more sanitary way to roll the dice at your next socially-distanced board game gathering? [CJA3D]’s pop-o-matic mason jar dice roller can roll the bones two different ways — either by hitting that big, inviting arcade button, or though a web app that everyone can access on their own phones.

We think this looks great, and is a great reuse of a glass jar. The brains of this operation is an ESP8266, which drives a continuous-rotation servo underneath the dice. Push the button or use the web app and the servo disturbs the plate, moving the dice around.

Besides the sanitary aspect, one benefit of using the web app is that there are four different speed presets for the servo. As a bonus, [CJA3D] included the files for a pair of printed 6-sided dice. Click through to the project to see it in action.

We know you take games seriously, and so do we. Just look at this dice roller that uses machine vision to ensure fairness.

This Tabletop Lighthouse Will Get Your Attention

October 4, 2020 by 7 Comments

If you wear headphones around the house with any regularity, you’re probably missing out on a lot of audio cues like knocks at the door, people calling your name, or maybe even the smoke alarm. What if you had a visual indicator of sound that was smart enough to point it out for you?

That is the point of [Jake Ammons’] attention-getting lighthouse, designed and built in two weeks’ time for Architectural Robotics class. It detects ambient noise and responds to it by focusing light in the direction of the sound and changing the color of the light to a significant shade to indicate different events. Up inside the lighthouse is a Teensy 4.0 to read in the sound and spin a motor in response.

[Jake]’s original directive was to make something sound-reactive, and then to turn it into an assistive device. In the future [Jake] would like to add more microphones to do sound localization. We love how sleek and professional this looks — just goes to show you what the right t-shirt stretched over 3D prints can do. Check out the demo after the break.

Seaside lighthouses once used gas lights giant Fresnel lenses, but now they use LEDs. A company in Florida is using CNC machines to crank out acrylic Fresnels.

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A Digital Magic 8-Ball? Signs Point To Yes

October 3, 2020 by 4 Comments

[FacelessTech] was recently charmed by one of our prized possessions as a kid — the Magic 8-Ball — and decided to have a go at making a digital version. Though there is no icosahedron or mysterious fluid inside, the end result is still without a doubt quite cool, especially for a project made on a whim with parts on hand.

It’s not just an 8-ball, it also functions as a 6-sided die and a direct decider of yes/no questions. Underneath that Nokia 5110 screen there’s an Arduino Pro Mini and a 3-axis gyro. Almost everything is done through the gyro, including setting the screen contrast when the eight ball is first powered on. As much we as love that aspect, we really like that [FacelessTech] included a GX-12 connector for easy FTDI programming. It’s a tidy, completely open-source build, and there’s even a PCB. What’s not to like? Be sure to check out the video after the break to see it in action.

Believe it or not, this isn’t the smallest Magic 8-Ball build we’ve seen. Have you met the business card version?

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Reel In The Years With A Cassette Player Synth

October 1, 2020 by 9 Comments

Variable-speed playback cassette players were already the cool kids on the block. How else are you going to have any fun with magnetic tape without ripping out the tape head and running it manually over those silky brown strips? Sure, you can change the playback speed on most players as long as you can get to the trim pot. But true variable-speed players make better synths, because it’s so much easier to change the speed. You can make music from anything you can record on tape, including monotony.

[schollz] made a tape synth with not much more than a variable-speed playback cassette player, an Arduino, a DAC, and a couple of wires to hook it all up. Here’s how it works: [schollz] records a long, single note on a tape, then uses that recording to play different notes by altering the playback speed with voltages from a MIDI synth.

To go from synth to synth, [schollz] stood up a server that translates MIDI voltages to serial and sends them to the Arduino. Then the DAC converts them to analog signals for the tape player. All the code is available on the project site, and [schollz] will even show you where to add Vin and and a line in to the tape player. Check out the demo after the break.

There’s more than one way to hack a cassette player. You can also force them to play full-motion, color video.

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Improved Mosquito Birth Control Causes Ripple Effect

October 1, 2020 by 29 Comments

Mosquito haters of the world, rejoice! A few years ago we told you about the first version of this solar-powered mosquito repellent that works by disturbing the surface of standing water. Since then, the project has received worldwide attention, and [Pranav] is back with Solar Scare Mosquito version 2.0 in time for the the 2020 Hackaday Prize.

The idea’s still the same as before: let mosquitoes lay their eggs in the standing waters of tanks and swamps, then disturb the water with vibrations so the larvae on the surface can’t breathe.

As smart as this simple idea is, version 2.0 is even smarter. It has a microphone that listens to the wing-beat frequencies of mosquitoes that like to hang around places like that.

Inside there’s an Arduino MKR GSM to run the ripple-generating air pump, detect water from the sensor, and gather data from the microphone.

With a network of these devices all reporting data, [Pranav] envisions an early warning system for mosquito-borne epidemics that works by alerting the locals through their phones.

Solar Scare Mosquito has come a long way since 2014. Check out the video after the break.

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A Good, Hard Look At Pre-Stressed Concrete

September 29, 2020 by 43 Comments

From the looks of the average driveway or sidewalk, it may seem as though concrete is just destined to crack. But if concrete is so prone to cracking, how are we able to use it in so many high-stress applications like bridges and skyscrapers? This question came about while I was researching 3D-printed thermite for an article. Thermite is often used in welding railroad tracks, and I linked a video of fresh tracks being welded that had concrete ties. I knew I had to find out how concrete could be made to withstand the pressure of freight trains.

On its own, concrete is brittle and has no give to it at all. But that doesn’t mean it isn’t strong. Although concrete has good compression strength, the tensile strength is quite poor. Around the late 1800s, someone thought to fortify spans of concrete with steel reinforcing bars, better known as rebar. Steel can stretch, adding steel bars gives the concrete some tensile strength to go along with its compressive strength. Rebar also allows for thinner slabs and other members.

Rebar Only Goes So Far

Parking blocks are meant to be replaced occasionally. Image via Checkers Safety

Rebar or mesh-enforced concrete is good for things like parking lot blocks and roads, but it still fails before it ought to. In fact, it usually has to crack before the rebar can chip in any of its tensile strength.

In high-stress concrete applications like bridges and skyscrapers, it’s terrifically important to avoid deflection — that’s when a concrete member flexes and bends under load. Deflection can cause the modern glass skins to pop off of skyscrapers, among other problems.

A solid, rigid bridge is much nicer to walk, drive, and bicycle on than a bridge that sways in the breeze. But how do you do make a rigid bridge? One solution is to apply stresses to the concrete before it ever bears the load of cars and trucks or a steady schedule of freight trains.

Pre-stressed concrete is like rebar-enforced concrete, but with the added power of tension baked in. By adding stress to the concrete before it goes into service, deflection will be reduced or perhaps eliminated altogether. With the addition of tensile strength, more of the concrete’s own strength is able to come into play.

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