DC Voltage at Line-In port

[syedmuzahirali]

Hi All,

I am making a PC sound card based Electromyograph, to record voluntary muscle activation. The output from the hardware will be sent to the soundcard using Line-In port. I have already made a circuit simulation of my Hardware which consists of an instrumentation amplifier, A wideband bandpass filter of frequency 15 - 550 Hz and a Full wave rectifier. Looking on the internet i have found that the line-in port can take upto 1.5Vrms input. The output of my hardware is in range to this value which i think is fine but the problem arises here. I am also getting DC voltage with the AC voltage at my output. I'm afraid that the circuit can still work. Could anyone out here help me with this. I am also attaching the circuit simulation file.

Regards,

Ali

 

[srizbf]

in your circuit you have used dual supply.
which will not produce any o/p dc voltage.

the last opamp tlo82 circuit can be modified to have an ac o/p.

or simply , to test connect a coupling cap of some medium value to line-in.

 

[kak111]

Maybe it is better to protect your sound card input,
like here...

1.
-add non polar 100nF...470nF series to input
https://www.edaboard.com/threads/235189/#post1004030

2.
- you can use only output pot´s from here
add non polar 100nF...470nF series (, just like in 6 inp. pot´s)
https://www.edaboard.com/threads/235189/#post1004843