Sciencemadness Discussion Board

Dumb Electronics Question

elementcollector1 - 9-2-2015 at 18:57

I've been designing some circuitboards in Eagle CAD to be printed at my university's router, but have run into a bit of a design problem. In the main circuitboard, an audio input jack is expected to do two things: Send an audio signal to a microcomputer elsewhere on the board, and send the same incoming audio signal to a second jack as an audio output (This board is designed to interface with an MP3, performing functions in addition to allowing the user to still listen to their music).

Now, if I wired the input to the microcomputer and the output to the other audio jack in parallel, I'd think the path of least resistance would be the output audio jack, and the electrons would just skip the microcomputer completely. Is this true? If so, how do I fix this so that the signal goes to both places?

WGTR - 9-2-2015 at 20:22

An ADC is a voltage-driven device. If the voltage is there, then the ADC sees it. Unless your audio output is a dead short, there will still be voltage there on that node.

At the same time, an MP3 player has a low source impedance, and doesn't supply much voltage for a given power output. Don't be surprised if the volume at the processor seems too low. An amplifier stage may be needed before the ADC.

So, what kind of router are you using?

elementcollector1 - 10-2-2015 at 06:25

Quote: Originally posted by WGTR  
An ADC is a voltage-driven device. If the voltage is there, then the ADC sees it. Unless your audio output is a dead short, there will still be voltage there on that node.

At the same time, an MP3 player has a low source impedance, and doesn't supply much voltage for a given power output. Don't be surprised if the volume at the processor seems too low. An amplifier stage may be needed before the ADC.

So, what kind of router are you using?


Good to know, and yes, I have an amplifier circuit built-in.
http://engineering.case.edu/thinkbox/equipment/pcbrouter

It's free for student use, which I'm going to take full advantage - I've got 6 other circuitboards (all of which are simply LEDs).

EDIT: For those of us who have Eagle (it's free, last time I checked!), the board files are attached.

Attachment: schematic1.sch (220kB)
This file has been downloaded 531 times

Attachment: schematic1.brd (85kB)
This file has been downloaded 470 times

[Edited on 2-10-2015 by elementcollector1]