66% or better

Un-crapifying a Car Stereo

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[Noah Farrington] has just accomplished a major milestone in his life, purchasing his first car! A glorious 2001 Ford Focus wagon. While it may be a fully loaded luxury vehicle, it is missing one thing poor [Noah] can’t live without. An aux-in port.

He had a few options for rectifying the situation. Live with it as is, hack the strange Ford media protocol out of the back, or fool the CD player into playing his input. Naturally he chose the third option.

His first challenge was removing the deck from the car. People told him he’d have to buy fancy stereo removal tools — he made do with tent pegs and coat hangers. Using the same method as described in a past aux-in hack, he identified the audio in leads on the CD player’s ribbon cable. By carefully soldering in his own aux-in plug, he’s almost ready for business! Unfortunately, the CD player also needs to think that it is on for it to properly output the audio. [Noah] chose the simple solution — record a silent CD to always leave in the deck.

Stick around after the break to see it in action.

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Sonar With Python and Conference Call Hardware

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[Jason] just tipped us off about his recent experiment, in which he creates a sonar system using standard audio equipment and a custom Python program. In case some of our readers don’t already know it, Sonar is a technique that uses sound propagation to detect objects on or under the surface of the water. It is commonly used in submarines and boats for navigation. [Jason]‘s project uses active sonar, which consists in sending short audio bursts (chirps) and listening for echoes. The longer it takes for the echo to return, the further the object is. Though his proof of concept is not used underwater, that may change if he continues the project.

The audio editing software Audacity was used to make a fast frequency changing chirp, along with PyAudio libraries for the main Python program. Exact time of arrival is detected by correlating the microphone output with the transmitted signal. Given that [Jason] uses audible frequencies, we think that the final result shown in the video embedded below is quite nice.
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DIY Hearing Aid

DIY Hearing Aid

Hearing aids are expensive little devices, typically costing a few thousand dollars each. They need to be highly integrated to fit in the ear, while still providing signal processing to ensure good audio quality.

This DIY hearing aid does some intelligent signal processing. It uses an electret to capture audio, then uses a pre-amplifier to increase the gain 100 times. The next stage consists of four filters, dividing the input signal by frequency into four parts. These are passed into four LTC6910 programmable gain amplifiers, which allow an Arduino to control the gain of each channel. The LTC6910 takes 3 digital inputs that are used to set the gain value.

To determine which gain to use for each frequency band, the Arduino needs to know how much power is in each band. This could be done using a Fast Fourier Transform, but that would require quite a bit of processing power. Instead, an envelope detector averages the signal, which can be read by an analog input on the Arduino. Using this information, the hearing aid can boost specific frequencies when it detects conversation.

This hearing aid won’t quite fit in your ear, but there is a lot of interesting signal processing going on. The schematic, Arduino source code, and a MATLAB simulation are provided.

Bluetooth Audio Adapter Hacked to Switch Off Amplified Speakers

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This Bluetooth Audio Adapter is meant to connect a Bluetooth audio source (like a smartphone or tablet) to a speaker system with a plain old line-in connection. It has the ability to automatically connection when the Bluetooth device comes into range. Sounds convenient until [Andreas Pösch] points out that he still has to switch the speakers on and off manually. This hack automates the entire thing using a bit of additional hardware.

If you look closely you’ll see that the black cables have barrel jacks. This is a power pass-through rig that he whipped up. The protoboard includes a 7805 linear regulator which feeds power to the green circuit board in lieu of it’s original power adapter. A MOSFET switches outbound power headed for the speakers. All of it fits inside of the original enclosure, and he only had to add one port for the AC adapter.

This would be absolutely perfect for an antique radio retrofit. One of these adapters can be had for just over thirty bucks!

Alas, Poor Yorick! I Tweeted Him

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You know Halloween is coming around when the tweet reading skulls start popping up. [Marc] wanted to bring the Halloween spirit into his workplace, so he built “Yorick”. In case you’re worried, no humans were harmed (or farmed for parts) in the creation of this hack. Yorick started life as an anatomical skull model, the type one might find in a school biology lab. Yorick’s skull provided a perfect enclosure for not one but two brains.

A Raspberry Pi handles his higher brain function. The Pi uses the Twitter API to scan for tweets to @wedurick. Once a tweet is found, it is sent to Google’s translate server. A somewhat well-known method of performing text to speech with Google translate is the next step. The procedure is simple: sending “http://translate.google.com/translate_tts?tl=en&q=hackaday” will return an MP3 file of the audio. To get a British accent, simply change to google.co.uk.

The Pi pipes the audio to a speaker, and to the analog input pin of an Arduino, which handles Yorick’s lower brain functions.  The Arduino polls the audio in a tight loop.  An average of the last 3 samples is computed and mapped to a servo position. This results in an amazingly realistic and automatic mouth movement. We think this is the best part of the hack.

It wouldn’t’ be fair for [Marc] to keep the fruits of his labors to himself, so Yorick now has his own Livestream channel. Click past the break to hear Yorick’s opinion on the Hack A Day comments section! Have we mentioned that we love pandering?

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Custom Wireless Headphone Charging Station

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We’ve come to expect quite a lot of convenience from our technology, to the point where repeatedly plugging in a device for recharging can seem tedious. Hackaday regular [Valentin Ameres] decided to ditch the plugs and built his own wireless headphone charger. We’ve seen [Valentin's] work before, and one thing’s for certain: this guy loves his laser cutter. And he should, considering it’s churned out key components for a gorgeous Arc Reactor replica and his Airsoft Turret. [Valentin] fired it up yet again to carve the charging stand out of acrylic, then used a small torch and the edge of a table to bend the stand into shape.

He sourced the needed coils online and soldered the receiving coil to a spare miniUSB plug. These components are glued onto a laser-cut acrylic attachment, which fits against the side of the headphone and is held in place by plugging directly into the earpiece’s miniUSB jack. The headphones rest on the laser-cut charging stand, which has an extrusion of acrylic on one side that holds the emitter coil in position against the receiver coil. [Valentin] also added a simple momentary switch at the top of the stand to activate both the emitter coil and a status LED when pressed by the headphones.

Stick around for a video of the build below, and check out some other headphone hacks, like adding a Bluetooth upgrade or making a custom pair out of construction earmuffs.

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Retrotechtacular: Discovering Electronic Music

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We take it for granted today that a lot of the music we hear includes synthesized instruments and sounds. But looking all the way back to 1983 for this Discovering Electronic Music video series provides a glimpse of the humble beginnings of the technology. The first five minutes of part one may annoy your aurally, but it’s worth it as that’s the point at which we get into sound generation using equipment like that seen above. All three parts in the series are embedded below; about twenty minutes of video in total.

Mixer boards and other control interfaces used today still have a large area of real estate devoted to knobs and adjustments. But they also include a ton of software processing options which weren’t available until computers became both affordable and ubiquitous. What’s shown in the video is a set of hardware interfaces that process signals from oscillators or alter recorded sound. We’ve spent a lot of time marveling about software defined radio and how it’s making RF hacking accessible to the masses. But who here hasn’t done at least a bit of tinkering in electronic music using any of the myriad of audio software? Would you have done that if you needed to build your own envelope and filter circuitry?

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