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connecting audio input


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#1 Jamie Lewis

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Posted 21 January 2012 - 12:58 AM

would it be safe to connect an audio output from my sound card direct to a netduino input?

#2 Geancarlo

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Posted 21 January 2012 - 04:15 AM

The audio output swings from -1 to +1V(as far as i know), while the netduino adc should only receive positive voltages below 3.3V I suggest you interface them with a voltage summing circuit using a rail-to-rail operational amplifier powered with 3.3V. The audio output from ur sound card should be added to 1.65V(3.3/2) so that you stay right in the middle of the adc range not reaching any of the limits.

#3 Jamie Lewis

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Posted 29 January 2012 - 11:58 PM

Hi Geancarlo, sorry for the late reply, i've been playing around trying to get my head around this but can't seem to figure it out. First, Ive taken two 3.5mm audio sockets and wired them on a breadboard ... taking audio from the laptop through the board and out the headphones. Then using a multimeter trying to get a reading which I can't seem to get. Secondly, i've got a LM358 op-amp ... this wired up to 3.3v regulator on the power pin gives a constant 2.01v on its output pins ... but I am unsure where to go from here to connect the audio up as anything i try doesn't seem to effect the outputs. Any ideas? Thanks Jamie.




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