Sparkfun MP3 Trigger Board

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The Sparkfun MP3 Trigger Board is a PCB that uses a micro SD card to generate Sound.
The Soundfiles stored on the SD card are triggered an via lineout you can hear them.
You’ll need an amp and a speaker or a battery powered speaker with line in.

Troubleshooting: If you use a Marcduino for triggering sounds and there’s no sound coming, please check if the mp3 files have the correct name/structure

Sparkfun MP3 Trigger

Improving the Sparkfun MP3 Trigger

All Info from (Images Copyright by Zach Poff)

B.Y.O. Line Output

The included audio output has a DC offset with respect to the power supply ground, so it’s only safe for driving headphones. Also, the static electricity from a long cable might fry the MP3 decoder chip.

Sparkfun provides a link to the chip’s datasheet with example line-out circuits, but it’s a bit confusing because some of the components are already on the board.

Long Cables Cause False Triggers! (solved…)

When attaching buttons to the trigger inputs on the board, you must use short cables (like 2ft or less). Long cables cause false triggering and crosstalk between the inputs. This seems to be caused by inadequate pull-up resistors on the inputs, so they have a tendency to “float” between high and low states when not actively triggered. (The MP3 Trigger’s multiplexer has a 680Ω pull-up resistor on each input, so I’m not sure why it’s so sensitive to long cables.) This problem has been mentioned on the designer’s forum a few times.

Some people have used shielded cable, restricted themselves to inputs 17 & 18 (which bypass the multiplexer) or added 1kΩ pull-up resistors to each input (the best option, but hard to implement).

I added a single 1kΩ pull-up resistor to the output of the multiplexer, and to my surprise it fixed the false triggers on all inputs, even with 25ft cables! Connect the resistor between pin 3 of the micro-controller and the large tab (3.3v) of the nearby voltage regulator.

Be careful and use a fine-tipped low-wattage soldering iron. Afterward, consider putting a dab of glue on the resistor to prevent it from damaging the micro-controller if bumped.

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