Reel In The Years With A Cassette Player Synth

October 1, 2020 by Kristina Panos 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 Kristina Panos 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 Kristina Panos 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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Split Keeb Splits Time Between Desk And Tablet Modes

September 29, 2020 by Kristina Panos 8 Comments

A keyboard you build yourself should really be made just for you, and meet your specific needs. If you approach it this way, you will likely break ground and inspire others simply because it’s personalized. Such is the case with [_GEIST_]’s highly-customized lily58, designed to work in two modes — on the desk, and mounted on the back of a tablet.

The lily58, which is a 58-key split with dual OLED footprints, was just a starting point for this build. For tablet mode, where the keyboard is attached to the back of a tablet with hook-and-loop tape, [_GEIST_] created custom plates that double the thumb keys on the back.

We love that there is a PSP thumbstick for mousing on one layer and inputting keystrokes on other layer. But we can’t decide which is our favorite part: the fact that [_GEIST_] threaded it through the bottom of a Kailh Choc switch, or the fact that there’s a Pimoroni Haptic Buzz with a different wave form for each layer. [_GEIST_] also added an acrylic middle plate layer to support quick-change magnetic tenting legs.

Keyboard mods don’t have to be involved to be adopted by others. This modified Dactyl adds custom wrist rest holders and has deeper bottoms that allow for less than perfect wiring.

Via reddit

Parking Assistant Helps Back Up The Car Without Going Too Far

September 27, 2020 by Kristina Panos 24 Comments

Sure, [Ty Palowski] could have just hung a tennis ball from the ceiling, but that would mean getting on a ladder, testing the studfinder on himself before locating a ceiling joist, and so on. Bo-ring. Now that he finally has a garage, he’s not going to fill it with junk, no! He’s going to park a big ol’ Jeep in it. Backwards.

The previous owner was kind enough to leave a workbench in the rear of the garage, which [Ty] has already made his own. To make sure that he never hits the workbench while backing into the garage, [Ty] made an adorable stoplight to help gauge the distance to it. Green mean’s he’s good, yellow means he should be braking, and red of course means stop in the name of power tools.

Inside the light is an Arduino Nano, which reads from the ultrasonic sensor mounted underneath the enclosure and lights up the appropriate LED depending on the car’s distance. All [Ty] has to do is set the distance that makes the red light come on, which he can do with the rotary encoder on the side and confirm on the OLED. The distance for yellow and green are automatically set from red — the yellow range begins 24″ past red, and green is another 48″ past yellow. Floor it past the break to watch the build video.

The humble North American traffic signal is widely recognized, so it’s a good approach for all kinds of applications. Teach your children well: start them young with a visual indicator of when it’s okay to get out of bed in the morning.

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Already Have That Book? Get The ISBN 411 Over IoT

September 27, 2020 by Kristina Panos 16 Comments

Have you ever been at the bookstore and stumbled across a great book you’ve been looking for, but had a nagging feeling that you already had it sitting at home? Yeah, us too. If only we’d had something like [Kutluhan Aktar]’s ISBN verifier the last time that happened to say for sure whether we already had it.

To use this handy machine, [Kutluhan] enters the International Standard Book Number (ISBN) of the book in question on the 4 x 4 membrane keypad. The Arduino Nano 33 IoT takes that ISBN and checks it against a PHP web database of book entries [Kutluhan] created with the ISBN, title, author, and number of pages. Then it lets [Kutluhan] know whether they already have it by updating the display from a Nokia 5110.

If you want to whip one of these up before your next trip to the bookstore, this project is completely open source down the web database. You might want to figure out some sort of enclosure unless you don’t mind the shy, inquisitive stares of your fellow bookworms.

Stalled out on reading because you don’t know what to read next? Check out our Books You Should Read column and get back to entertaining yourself in the theater of the mind.

Via r/duino