Simple Bluetooth Car Audio From A Pi Zero

When [Sami Pietikäinen] realized that the Bluetooth built into his car didn’t support audio, he didn’t junk it and buy a Tesla. Instead, he decided to remedy the problem by building a small Bluetooth device that plugged into the Aux socket. To do this, he used a Raspberry Pi Zero with a pHAT DAC (Digital to Audio Converter). That’s perhaps using a sledgehammer to crack a walnut, but sometimes you work with what you have. The interesting part is to be found in what he did next: he used Yocto to optimize the device down to make it as simple and straightforward as possible.

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1940s Portable Radio Is A Suitcase

The meaning of the word portable has changed a bit over the years. These days something has to be pretty tiny to be considered truly portable, but in the 1940s, anything with a handle on it that you could lift with one hand might be counted as portable electronics. Zenith made a line of portable radios that were similar to their famous Transoceanic line but smaller, lighter, and only receiving AM to reduce their size and weight compared to their big brothers. If you want to see what passed for portable in those days, have a look at [Jeff Tranter’s] video (below) of a 6G601 — or maybe it is a GG601 as it says on the video page. But we think it is really a 6G601 which is a proper Zenith model number.

According to [Jeff], 225,350 of these radios were made, and you can see that it closes up like a suitcase. The initial 6 in the model number indicates there are 6 tubes and the G tells you that it can run with AC or batteries.

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Itty Bitty MIDI Piano Sings With Solenoids

Toy pianos are fun to plink around on for a minute, but their small keyboards and even smaller sound make them musically uninteresting pretty quickly. [Måns Jonasson] found a way to jazz up a two-octave toy piano almost beyond recognition. All it took was thirty solenoids, a few Arduinos, a MIDI shield, and a lot of time and patience.

This particular piano’s keys use lever action to strike thin steel tines. These tines are spaced just wide enough for tiny 5V solenoids to fit over them. Once [Måns] got a single solenoid striking away via MIDI input, he began designing 3D printed holders to affix them to the soundboard.

Everything worked with all thirty solenoids in place, but the wiring was a bird’s nest of spaghetti until he upgraded to motor driver shields. Then he designed a new bracket to hold eight solenoids at once, with a channel for each pair of wires. Every eight solenoids, there’s an Arduino and a motor shield.

The resulting junior player piano sounds like someone playing wind chimes like a xylophone, or a tiny Caribbean steel drum. Check out the build video after the break.

Hate the sound of toy pianos, but dig the convenient form factor? Turn one into a synth.

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Mix And Match Parts To Build A Better Mountain Bike Derailleur

Mountain bikers take their sport seriously, and put their bikes through all manner of punishment in the course of a ride. This has given rise to a wide range of specialist equipment, such as suspension, disc brakes and even clutch derailleurs, which help reduce chain slap when riding over rough terrain. However, these specialist derailleurs aren’t available for all applications, so sometimes you’ve gotta hack together your own.

Shimano clutch derailleurs are only really available for 10-speed rear cassettes and up, due to a change in derailleur ratio compared to the earlier 6 to 9 speed cassettes. Using a derailleur designed for 10-speed operation on a rear cassette with fewer gears won’t shift properly.

[SzurkeEg] was inspired by earlier work, and realised that by combining parts from several generations of Shimano hardware, it was possible to build a working clutch derailleur for 6 to 9 speed rear cassettes. The main parallelogram is what handles the positioning of the derailleur, and is sourced from a 9-speed part to get the gear indexes correct.The rest of the parts are sourced from later models with the clutch feature built in.

It’s a smart mechanical hack, and one that isn’t necessarily the most intuitive. But by having a go, and seeing what’s possible, now a whole generation of mountain bikes can tear up the trail like never before. We’ve seen Shimano gear hacked before, too. Video below the break. Continue reading “Mix And Match Parts To Build A Better Mountain Bike Derailleur”

Bolt-On Stepper Motor Driver For The Raspberry Pi

For his entry into the 2019 Hackaday Prize, [Tobius Daichi] is working on adding some motion control capabilities to everyone’s favorite Linux SBC. His 3+Pi board attaches to the Raspberry Pi’s GPIO header and gives you a convenient way to control four individual stepper motors. Perfect for a 3D printer, laser cutter, CNC, or anything else you can think of that needs to move in a few dimensions.

But such a simplistic description of the 3+Pi might be underselling it a bit. While [Tobius] says he was inspired by the classic Arduino CNC Shield that powers countless DIY 3D printers, he’s managed to improve on the concept. Rather than having the host Pi communicate directly with the stepper drivers, the 3+Pi features an onboard STM32F302CBT6 that handles the actual motor control. The Pi just needs to tell it what to do over UART.

If you’re looking to do things in real-time, having an onboard microcontroller handle the low-level aspects of talking to the stepper drivers can be a big help. A natural extension for this board could be support for the Klipper firmware, which leverages the fact that the Raspberry Pi is many times more powerful than your average 3D printer control board. With the Pi handling the math and providing the microcontroller instructions, Klipper allows for faster and more accurate printing than the microcontroller alone could accomplish.

As for the stepper drivers themselves, [Tobius] has decided to go with the Trinamic TMC2041-LA-T. This chip is notable as it puts dual drivers in one 48-QFN package, which is great if you’re looking to save space on your board. Some might complain that the 3+Pi doesn’t allow for easily swapping out the stepper drivers if you manage to cook one like on the Arduino CNC shield, but realistically you could say the same about many purpose-built stepper control boards.

[Tobius] is tackling this project by himself currently, but does mention that he’s open to teaming up with anyone who’s got an interest in this sort of thing. There have been previous attempts at creating Linux-powered 3D printer controllers in the past, but we think this approach holds particular promise if for no other reason than the Raspberry Pi’s popularity.

Retrotechtacular: Predictions That Just Missed It

Few occupations are more fraught with peril than predicting the future. If you are a science fiction author, it might not matter, but if you are trying to design the next game-changing piece of hardware, the stakes are higher.

It seems like, for the most part, even if you manage to get some of the ideas right, the form is often way off. Case in point: telemedicine. Today you can visit a doctor using video conferencing with your phone or a PC for many common maladies. A new idea? Not really. Hugo Gernsback wrote about it in Radio Electronics back in 1955.

Gernsback wrote:

The average medical doctor today is overworked and short-lived. There are never enough doctors anywhere for the world’s constantly multiplying population. Many patients die because the doctor cannot reach them in time, particularly at night and in remote regions.

…[H]e can only see a few [patients] during the day. With increasing traffic congestion, many doctors refuse to make personal calls — execept in emergencies. Even then they arrive often too late. Much of this dilemma will be archaic in the near future, thanks to the Teledoctor.

Gernsback envisioned a doctor using what we now call Waldos similar to what people use to manipulate radioactive material. These super mechanical hands (Gernsback’s words) would allow the doctor to write a prescription, pour liquids, or even diaper a baby thanks to a sense of touch built into them.

Oddly enough, Gernsback’s vision included renting a teledoctor from the drugstore for $3.50 a day. This way, the doctor could call on you and then follow up as well. The drug store would deliver the machine and it would — get this — connect to your phone:

A cord with the a telephone plug attached to the teledoctor instrument is now plugged into a special jack on your telephone. Future telephones will be provided with this facility. The TV signals and telehand electronic signals, etc., will all travel over the closed circuit telephone lines.

In a footnote, Gernsback notes that you can’t send a 525-line TV signal on current phone lines, but a 250-350 line picture was possible and that would be sufficient.

Visionary? In some ways, maybe. The basic idea is coming true today, although it isn’t likely doctors will do surgery or inject you remotely in your home anytime soon. The special telephone plug sort of came true and is already obsolete. The images, by the way, are the ones that accompanied the original article in Radio Electronics.

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Electric Dump Truck Tricycle Is No Toy

There are some utility bicycles on the market, some with electric motors to help carry a good bit of cargo. If you really need to haul more weight than a typical grocery-getter like this, you’ll want to look into a tricycle for higher capacity loads. Nothing you’ll find will match this monstrous electric tricycle hand-built by [AtomicZombie] out of junkyard parts, though. It’s a mule.

Since [AtomicZombie] sourced most of the underpinnings of this build from the junkyard, it’s based on an old motorcycle frame combined with the differential from a pickup truck, with a self-welded frame. He’s using an electric motor and a fleet of lead acid batteries for the build (since weight is no concern) and is using a gear reduction large enough to allow him to haul logs and dirt with ease (and dump them with the built in dump-truck bed), and even pull tree stumps from the ground, all without taxing the motor.

[AtomicZombie] documented every step of the build along the way, and it’s worth checking out. He uses it as a farm tractor on his homestead, and it is even equipped with a tow hitch to move various pieces of equipment around. Unlike a similar three-wheeled electric contraption from a while back, though, this one almost certainly isn’t street legal, but it’s still a blast!

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