Didn't you say that this signal was going to feed the input of an ADC and that's why you needed 0 to +5V? Did I miss when it was changed to a Mic input on a PC?

Not to be a snot, but the audio inputs on a PC ARE an ADC of sorts.

 

Not to be a snot, but the audio inputs on a PC ARE an ADC of sorts.

The mic input is capacitively coupled and could care less whether the signal goes negative.

 

@wayneh
correct me if m not getting u...but my input signal(-10V to 10V) is just a voltage signal that is fed from a function generator to the hardware circuit that i posted above...and the harware circuit's output is a voltage signal of 0-5 volt and current in nano amperes....i wanted to ask that how can i give this ouptput signal to the mic port of PC..??

 

The Mic input on modern PCs are designed to work with Electret Microphones, where the PC supplies a DC voltage to the mic element via a ~10K resistor. If you plug in a bare mini plug you can measure this voltage. Electret microphones have much higher output than dynamic mics. To answer your question, use a voltage divider and a coupling cap.

 

Like someone said before, opto isolator is very non-linear, unless you use some auto-linearizing scheme with feedback. They are made for digital signal.

Actually, I was rather surprised by these results. It's not instrument accuracy quality but it's better than I thought I'd get.

 

@wayneh
correct me if m not getting u...but my input signal(-10V to 10V) is just a voltage signal that is fed from a function generator to the hardware circuit that i posted above...and the harware circuit's output is a voltage signal of 0-5 volt and current in nano amperes....i wanted to ask that how can i give this ouptput signal to the mic port of PC..??

The mic input may have variable gain, but I suspect 5v is too much for it, so you'll see clipping unless you divide it down to 1v or so. Beware of connecting your computer's ground to anything else that may have a path to "ground". Too much current can blow your input.

 

thanx CDRIVE & wayneh..

and what about the current level..is the nano amperes of current too much for mic port...m geting some 300nA....should i decrease the current level also..??

 

If the peak voltage is kept @ 1V or lower the current will take care of itself.

 

If the peak voltage is kept @ 1V or lower the current will take care of itself.

+1
Current isn't an issue

 

thank u ppl..

i brought down the signal to 0-0.5V to give it to mic port...want to ask that how should i connect this output from breadboard to mic port...is there any cable that i can use..???

 

thank u ppl..

i brought down the signal to 0-0.5V to give it to mic port...want to ask that how should i connect this output from breadboard to mic port...is there any cable that i can use..???

All you need are the right connectors, and I think shielding will be very helpful.

I recommend not connecting the grounds directly (computer ground to your new device ground) until you know that is safe. Use something like a 200Ω resistor and look for millivolts across it, or heat.

 

The mic jack is a 1/8" stereo mini plug. You can buy the bare plug or buy an audio patch cable and cut it in half.

 

The mic jack is a 1/8" stereo mini plug. You can buy the bare plug or buy an audio patch cable and cut it in half.

I often grab the free headphones you get on a long flight, just so I can have a supply of plugs to grab for such things. But they're not really as good as a shielded plug - as you'd get from the patch cable - for this particular use.

 

Snip: I often grab the free headphones you get on a long flight, ....

So, it's because of you that it cost so much to fly!