Problems with condenser microphome circuit

This form is for general electronics discussions, but, not PSoC.

Moderator: ericb

Forum rules
As you would expect spam, vulgar language, or discussions not related to electronics are banned from this forum.

Problems with condenser microphome circuit

Postby arivalagan13 » Mon Feb 11, 2013 10:55 am

Hi developers,
I need to build an microphone circuit for one of my projects..
I built the circuit shown in the link http://www.ece.ucsb.edu/yuegroup/Teachi ... /Lab1b.pdf
I built and tested the preamplifier circuit it works well for sinusoids...
But the moment I connect the MIC it is not showing any response(as I talk towards it)...
I biased the MIC as shown in the given link...
I understood in the case of MIC I should get a noisy waveform in idle state as it will pick noise signals present in the environment..But it reads only zero..
If I did bias the MIC as shown in the document there was a voltage drop of around 3 volts..
Can somebody help me to resolve the issue..

Regards
Arivalagan M
arivalagan13
Cheese Wheel
Cheese Wheel
 
Posts: 129
Joined: Sun Dec 23, 2012 3:32 am

Re: Problems with condenser microphome circuit

Postby arcs_n_sparks » Tue Feb 12, 2013 1:38 pm

Could you provide details on the actual microphone you selected?
arcs_n_sparks
Cheese Cube
Cheese Cube
 
Posts: 36
Joined: Wed Nov 22, 2006 5:03 pm

Re: Problems with condenser microphome circuit

Postby danadak » Thu Feb 14, 2013 5:23 am

Electrets are not all equal, in loading, integration, etc.. Also many incorporate
a JFET to buffer their inherent high Z of the electret. JFETs can be pretty static
sensitive on their gate, not necessarily catastrophic failure, eg. degradation of per-
formance can result.

Look at datasheet for recommended loading, and modify circuit you are using.
Note the circuit as shown presents ~ 2K load to the electret, which seems low.
Thats controlled by bias divider and input R to first OpAmp. You could scale the
OpAmp R's (input and fdbk) by 10 and input bias network by 10 as a possibility.
Although this increases Johnson noise, albeit by square root.

Regards, Dana.
Field Application Engineer
KB1RHB Mostly listen :)
Semi Retired
User avatar
danadak
The Big Cheese
The Big Cheese
 
Posts: 2008
Joined: Thu Dec 27, 2007 8:42 am
Location: New Hampshire

Re: Problems with condenser microphome circuit

Postby arivalagan13 » Thu Feb 14, 2013 10:56 pm

@ arcs_n_sparks:
I bought the one from local market where the knowledge of part number is not know..anyway i'll try to get it.

@ Dana:
I'll try the suggested changes and share the result

Regards
Arivalagan M
arivalagan13
Cheese Wheel
Cheese Wheel
 
Posts: 129
Joined: Sun Dec 23, 2012 3:32 am

Re: Problems with condenser microphome circuit

Postby arivalagan13 » Fri Feb 15, 2013 9:50 am

I made the biasing resistors 100K instead of 10K...also I scaled up the R1 & feedback resistors of first stage amplifier by 10...
Still not getting any response..should I increase the resistances further?

If electret mics are prone to static, how do i overcome the problem?

I wonder if such problems are associated with mics how they could be this much famous... :mrgreen:
arivalagan13
Cheese Wheel
Cheese Wheel
 
Posts: 129
Joined: Sun Dec 23, 2012 3:32 am

Re: Problems with condenser microphome circuit

Postby danadak » Fri Feb 15, 2013 1:46 pm

No further scaling should be done, as you will start generating noise and
a lot of offset in the amps.

If you have a function generator test the amp and measure the bias with a DVM
to eliminate signal conditioning as the suspect. If the rest of the signal path is good,
then that leaves a defective electret as primary suspect.

Static protection is an involved subject, normally basic approach is use diodes to
clamp wrong polarity signals. But Google this topic, much to learn.

Regards, Dana.
Field Application Engineer
KB1RHB Mostly listen :)
Semi Retired
User avatar
danadak
The Big Cheese
The Big Cheese
 
Posts: 2008
Joined: Thu Dec 27, 2007 8:42 am
Location: New Hampshire

Re: Problems with condenser microphome circuit

Postby arivalagan13 » Fri Feb 15, 2013 11:31 pm

Before connecting the MIC, i tested the amplifier circuit with sinusoidal inputs of various frequencies and i got nice clean sine wave at all instances..
arivalagan13
Cheese Wheel
Cheese Wheel
 
Posts: 129
Joined: Sun Dec 23, 2012 3:32 am

Re: Problems with condenser microphome circuit

Postby arivalagan13 » Tue Feb 26, 2013 3:18 am

Having faced many problems i thought of using a ordinary Headphone with MIC that we used in computers..
Now i want to connect the MIC to the circuit which has built (link is in one of my above posts)..

I got a monopin jack(thats what the local vendor calls it here).. to connect the headphone output to the circuit..

It(jack) has three pins at its output...i want to connect this to the circuit..i donno which one to connect where..

Kindly help me in making the connections... I attached the screen shot of the jack..pls have a look at it and suggest a way to solve this problem..

Regards
Arivalagan M
Attachments
project icons.zip
(1.29 MiB) Downloaded 144 times
arivalagan13
Cheese Wheel
Cheese Wheel
 
Posts: 129
Joined: Sun Dec 23, 2012 3:32 am

Re: Problems with condenser microphome circuit

Postby danadak » Tue Feb 26, 2013 7:19 am

On headphone plug, if its stereo, looks normally like this -

Headphone Jack.png
Headphone Jack.png (3.45 KiB) Viewed 4345 times


The tip and the next section/cyclinder are the signal connections, and the longer
metal section/cylinder ground. If its a mono jack the small section/cylinder next to tip
is not present.

Regards, Dana.
Field Application Engineer
KB1RHB Mostly listen :)
Semi Retired
User avatar
danadak
The Big Cheese
The Big Cheese
 
Posts: 2008
Joined: Thu Dec 27, 2007 8:42 am
Location: New Hampshire

Re: Problems with condenser microphome circuit

Postby arivalagan13 » Tue Feb 26, 2013 8:43 am

I use the MIC i378MV from iball

http://www.homeshop18.com/iball-i378mv- ... /cid:3270/

It says i i need 3.5mm jack of stereo type(mini stereo plugs or headphone plugs)..

If so how should i connect it to the circuit with reference to pictures i sent above...(my MIC is fitting nicely into the jack which i got from the local vendor..)

There are three pins coming out of the jack .. in one side provision for connecting MIC...to its exact opposite side two pins and to its right angle side one more pin...totally three pins..
Now how should i connect this to my circuit?
arivalagan13
Cheese Wheel
Cheese Wheel
 
Posts: 129
Joined: Sun Dec 23, 2012 3:32 am

Re: Problems with condenser microphome circuit

Postby danadak » Tue Feb 26, 2013 9:22 am

The only sure way is to contact Iball. That being said this reference shows
a mike and headphone connections on 3.5 mm plug -

http://en.wikipedia.org/wiki/Phone_connector_(audio)

Regards, Dana.
Field Application Engineer
KB1RHB Mostly listen :)
Semi Retired
User avatar
danadak
The Big Cheese
The Big Cheese
 
Posts: 2008
Joined: Thu Dec 27, 2007 8:42 am
Location: New Hampshire

Re: Problems with condenser microphome circuit

Postby arivalagan13 » Sun Mar 03, 2013 10:49 pm

Well..is it possible to for you to suggest any other way of doing this?

I just want to connect the microphone to my circuit..then using PSoC1 convert the speech signals into array of digital values and then do some control...

Regards
Arivalagan M
arivalagan13
Cheese Wheel
Cheese Wheel
 
Posts: 129
Joined: Sun Dec 23, 2012 3:32 am

Re: Problems with condenser microphome circuit

Postby danadak » Mon Mar 04, 2013 4:22 am

Did you try this from my prior post ?

220px-Jackplug-wiring.jpg
220px-Jackplug-wiring.jpg (19.36 KiB) Viewed 4294 times


Regards, Dana.
Field Application Engineer
KB1RHB Mostly listen :)
Semi Retired
User avatar
danadak
The Big Cheese
The Big Cheese
 
Posts: 2008
Joined: Thu Dec 27, 2007 8:42 am
Location: New Hampshire

Re: Problems with condenser microphome circuit

Postby arivalagan13 » Mon Mar 18, 2013 10:09 pm

Yes,i tried it and now the microphone circuit works..
Thanks Dana
arivalagan13
Cheese Wheel
Cheese Wheel
 
Posts: 129
Joined: Sun Dec 23, 2012 3:32 am


Return to “%s” General Electronics Discussion

Who is online

Users browsing this forum: No registered users and 1 guest