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November 2014
The Circuit
The circuit is self-explanatory except, perhaps, for the connections to the 8 ohm loudspeaker. The MP3 module has two
connection pins for a single speaker - SPK1 and SPK2. I've arranged it such that a pair of stereo headphones connect in the
usual way - ie each channel is connected between either SPK1 or SPK2 and Ground. Removing the headphones plug connects
the internal 8 ohm 0.1W speaker between SPK1 and SPK2 instead of connecting one side to ground.
The Printed Circuit Board
 
 
MOD-1021 MP3 micro-SD Audio Module | embedded adventures SoundOut MP3 Audio Module |
1" x 2.4" x 3.8" Enclosure (includes PP3 battery clip) | Farnell
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5-way Navigation Switch (ALPS - SKQUCAA010) | Farnell, CPC,
ebay |
3.5mm switched stereo socket | Farnell |
MCP1702-3302E 3v3 LDO Low Quiescent regulator | Farnell |
Miniature right-angle SPDT PCB mounting slide switch | ebay |
36mm dia. 8 ohm 0.15W loudspeaker |
Farnell, ebay |
ATtiny84 ATMEL Microcontroller | ebay |
14-pin DIL socket | ebay |
3mm LED, Resistors, 2 x 8 way pin headers, 1uF Electrolytic Capacitor, 47uF Electrolytic Capacitor | ebay |
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