The music player described is a stand alone player that plays WAV files from a microSD card at room filling volume. This is my first instructable, hopefully it will be easy to follow.
The ATTINY microcontroller produces a PWM (pulse width modulated) output that is filtered and amplified by a LM386 amplifier. The microcontroller circuit and code is from the ELM ChaN website: http://elm-chan.org/works/sd8p/report.html
The ATTINY85 will need to be programmed using the code available free from the ELM ChaN website.
Step 1: Building the Circuit
The circuit is constructed on stripboard and is straight forward, the socket used for the microSD is a microSD to SD card convertor with wires soldered directly to the contacts on the convertor. The component values are shown on the schematic and reference to this should be made when placing the components on the stripboard.
Step 2: Wiring the Controls and Speaker
The loudspeker, volume control and switches are connected to the circuit board with pvc covered wire.
Step 3: The Baffle Case
The case is a simple loudspeaker baffle with open back, the design of the speaker fret was cut using a fret saw and the circuit board and battery are mounted to one of the stands. The baffle is made from 3mm ply and the stands from MDF offcuts.
Step 4: Operating Instructions
Audio files can be downloaded from a PC to the microSD card. The player will only play audio files in the WAV format, to convert audio files to WAV. Variouis convertors are available to download for free from the internet. For Windows I use 'Free MP3 Wma' from Koyote Software, this can be downloaded from:
Select output format as: WAV
Select parameter as: PCM 44.100kHz, 8 Bit, Mono
The player initially looks for a directory labelled ‘wav’ on the micro SD card. If the directory does not exist, it will play wav files located in the root directory of the micro SD card.
To play audio files, ensure that a 9V battery is installed. Insert the micro SD card and turn the player on. Adjust volume control to the desired level. To advance tracks, simply press the advance button.