Bluetooth Cassette Adapter

September 11, 2011 by Brian Benchoff 27 Comments

Today, with iPods that can hold entire music collections and cell phones that stream music from the Internet, the lowly cassette seems like an anachronism. [Matt] still has a cassette deck in his truck, but wanted Bluetooth connectivity for his stereo. The obvious solution was to stuff Bluetooth headphones into a cassette adapter.

Audio cassette adapters are dead-simple devices. They’re really just a tape head, stuffed into the shell of a cassette and a wire going out to a media player. To put Bluetooth into his adapter, [Matt] got a cheap pair of Bluetooth headphones and tore them apart. He was left with a circuit board, battery, and two earphones. [Matt] cut off the leads to the ear phones and wired them to the cassette adapter head. After a little bit of modifications to the case, [Matt] had a functional Bluetooth-cassette adapter.

While it’s true [Matt] could have gotten a ready-made Bluetooth cassette adapter shipped from China to his door for $10, there’s not much fun in just buying one. Kudos to [Matt] for going the home-brew route.

Program An Arduino Using Your Sound Card

September 9, 2011 by Mike Nathan 86 Comments

audioino_programming_arduino_with_sound

[Chris] wrote us to share a neat technique he has been using to program the Arduinos he uses in his projects. He likes to build bare bones Arduino clones rather than sacrifice full dev boards, and instead of programming them via traditional means, he is using his computer’s sound card.

He builds a simple dead bug Arduino (which he calls an Audioino) using a handful of resistors, a pair of caps, an LED, a reset switch, and most importantly – an audio jack. After burning a special audio bootloader to the chip, he can connect the Arduino directly into his computer’s speaker port for programming.

Once the microcontroller is connected to his computer, he runs the IDE-generated hex file through a Java app he created, which converts the data into a WAV file. With the Arduino put into programming mode, he simply plays the WAV file with an audio player, and the code is uploaded.

He says that this method of programming comes in handy in certain cases where he builds things for friends, because they can easily update the software on their own without a lot of fuss.

Spectrum Analyzer Users Custom Characters On An HD44780 Display

September 8, 2011 by Mike Szczys 8 Comments

[Camilo] built a spectrum analyzer to use with his audio system (translate). The hardware is quite simple, using an op-amp, microcontroller and LCD display. He chose an LMV324M low-voltage op-amp which connects to the incoming audio signal and feeds its output to the microcontroller’s ADC. In this case, he chose a Freescale microcontroller from the HCS08 family which is running at 20 MHz. This gives the project enough speed to properly analyze the incoming audio. He mentions that he’s following the guidelines set forth in the Nyquist-Shannon sampling theorem and using the Fast Fourier Transform when processing the samples.

This isn’t the first time we’ve seen a character LCD used as a display for a frequency analyzer. This other ATmega8-based rendition supported several different screen layouts. These displays have enough RAM to store eight custom characters. Each character is 5×8 pixels, lending eight levels to each character for a total of 16 for each column seen above. We love the simplicity of the hardware in the project but we wouldn’t mind seeing an additional potentiometer to fine-tune how the data is displayed on the screen to take advantage of its full range. See the project in action in the clip after the break.

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PIC-based Voice Recorder

September 3, 2011 by Mike Szczys 34 Comments

[Vinod] just finished building a voice recorder and it turned out even better than he thought it would. The video after the break shows him recording what is surely one of your favorite songs from his cellphone and then playing it back. The audio quality does sound quite good for a project with very few components.

A PIC 16F877A makes up the majority of the build. Its ADC is used to capture the incoming line from an amplified microphone input (you’ll find that amp schematic half way through his post). He’s storing the data on an MMC card, which was a bit of a hack since the PIC has limited RAM to manage that overhead. The stored data is in a raw format, as the card is not accessed using a file system. This makes it easy to record at a high bit rate, leading to better audio quality. Playback consists of connecting a speaker via a low-pass filter and amplifier circuit to the hardware PWM output on the PIC.

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Speaker-mounted WAV Player For Street Performances

August 29, 2011 by Mike Szczys 21 Comments

This naked speaker is the basis for [MaoMakMaa’s] newest project called the Wavedrone. He plans on using the autonomous and cable-less device during street performances. You can hear the effect of some stretched jazz cords being played on it in the video clip after the break. The sound is kind of an ethereal background noise that observers might not immediately realize is there.

You can see the 9V battery which serves as the power source clinging to the frame of the speaker. A 7805 linear regulator tames that battery and feeds the two IC’s on the circuit board seen to the right. The ATtiny85 is reading music from an SD card and playing it back in mono (obviously) with the help of an LM386 audio amplifier chip. The trimpots that go into the high pass and low pass filters in between the microcontroller and amplifier allow for a bit of sound manipulation, but we’re more impressed with the quality of the sound this is getting when properly trimmed.

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Cellphone Controlled Retro-radio Stores And Plays Your Digital Library

August 24, 2011 by Mike Szczys 6 Comments

[Autuin] was worried about having desirable electronics stolen while on the road with his band. He didn’t want to take a laptop along on tour, but he didn’t want to be without his music either. To solve this problem, he built a music player inside of a cheap-looking radio. His write-up covers two different portable MP3 solutions, but it’s the second rendition that catches our attention.

After hollowing out the old radio he filled the void with an Asus WL-HDD 2.5. That hardware is meant to be an easy way to add network storage; it houses a laptop hard drive and has WiFi and Ethernet connectivity. But it also has one USB port, and can be hacked to add a second. [Autuin] did just that, using the two USB connections to add a Bluetooth dongle and a USB sound card. Music is synced with the hard drive via some cat-5 cable that’s hidden in the battery compartment of the vintage box. The NAS runs Linux, and the audio playback software is controlled though a Mobile Java application running on a somewhat broken cellphone. That’s an idea that might find its way into our next project.

Hacking A2DP Support Into An Old Car Stereo

August 22, 2011 by Mike Nathan 21 Comments

a2dp_tape_deck_retrofit

[Roofus] had an older car, and unfortunately his stereo’s cassette player just wasn’t doing it for him. He always wanted to simply get into his car, pull out his cell phone, and have his music ready to play without any fuss. After messing around with all sorts of different tape adapters, he got fed up and decided to rig up an A2DP (Stereo Bluetooth Audio) adapter on his own.

He pulled the head unit out and started looking around to see how he could wire an adapter in. He figured the best course of action would be to remove the tape deck, and fool the stereo into thinking that a tape had been inserted. After spending some time tracing wires and studying how his old tape adapters worked, [Roofus] had an A2DP connection wired in and was ready to rock out.

Greeted with nothing but silence, he turned to his favorite hacking site (Hackaday, naturally) for assistance. Some friendly forum-goers helped him identify a ground loop issue, and he set off to his nearest RadioShack for a pair of isolation transformers that would fix his problem.

Once he knocked out the ground loop issues, his adapter worked like a charm. He put everything back together, and aside from a tiny switch he installed to toggle between audio sources, you would never know it was there.