Hello SparkFun Forum
Started working with a PIR sensor to turn on a circuit.
Then the PIR circuit was connected to the Arduino,
first to operate an LED and then to play a track on
the SparkFun MP3 shield thru headphones.
Yesterday I incorporated a couple of SparkFun mono amplifiers
https://www.sparkfun.com/products/11044
But the amplifiers are 1.4 watt and not very loud. The
mono amp Quick Start Guide
https://www.sparkfun.com/tutorials/392
has a hack for increasing the amplifier amplitude
(loudness) by decreasing the gain resistors but
a volume pot is a preferred solution because it is
more flexible.
http://www.allenpitts.com/electronics/P … 150401.gif
Unfortunately I purchased a Velleman amplifier
K4003 before I saw the SparkFun Audio Amplifer Kit
STA540.
http://www.vellemanusa.com/products/view/?id=350530
The instructions on the K4003 show three ways of connecting
the amplifier to power: A ring-core transformer,
two twelve volt batteries, and a center tap transformer.
I have the center tap transformer.
http://www.allenpitts.com/electronics/K … hookup.gif
The question is about grounding the signal from
the SparkFun MP3 shield.
The Velleman instructions show a ground wire coming
in from the audio source, in this case the MP3 shield
and the Arduino Uno, to a 22K pot and out to a ground pin on the
K4003 amplifier.
But the K4003 amplifier is grounded to the transformer
so it seems like the amplifier system has two different
grounds: one at the transformer and one at the
Arduno/MP3 shield. (But the Arduno/MP3 shield is powered by
the SparkFun Product number TOL-00298
Wall Adapter Power Supply - 9VDC 650mA. So is
the Arduno/MP3 shield grounded to the house mains
just as the transformer is grounded to the house mains?)
Or should I set up a little voltage regulator circuit like
http://www.allenpitts.com/electronics/1 … ircuit.gif
between one side of the center tap transformer to create
a power supply for the Arduino/MP3 Shield so the amplifier and the Arduno/MP3 shield
are both grounded to the transformer?
Thanks.
Allen in Dallas