Is my MAX9814 mic shorted or damaged?

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exceptdefeat
 
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Is my MAX9814 mic shorted or damaged?

Post by exceptdefeat »

I bought the MAX9814 mic with amplifier, link below. I wrote some code for reading in samples and I'm using an FFT library and I've been testing it and am not seeing the output I expect. I didn't immediately solder the headers to the board. Instead, I've been testing my code by holding the board tightly against the headers and I'm worried that I may have shorted it out by doing that.

I didn't test the board with my multimeter when I got it, but after soldering the headers to the board, I'm testing the output and I'm getting a constant +1.2 V on the output pin. The power supply I'm using to drive it is putting out +5.4V, which should be safe, I believe. I have the board connected the way that the overview link shows (with the gain pin connected to Vcc and AR pin not connected).

Is the board damaged or am I just doing something wrong?

https://learn.adafruit.com/adafruit-agc ... 4/overview

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Franklin97355
 
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Re: Is my MAX9814 mic shorted or damaged?

Post by Franklin97355 »

Could you post clear pictures of your board and the connections to it? I'll check on the voltage but a mic needs to swing the voltage and I would expect the quiet voltage to be somewhere above 0.

exceptdefeat
 
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Re: Is my MAX9814 mic shorted or damaged?

Post by exceptdefeat »

Hi, thanks for responding. Yes, I'm aware that the output should be oscillating and changing quite a bit. Hence why I'd suspect that a nearly constant output would mean it's damaged, though I'm certainly not an expert. Some pics attached below.
Board connections.
Board connections.
IMG_20140713_165233.jpg (360.9 KiB) Viewed 403 times
The power supply voltage.
The power supply voltage.
IMG_20140713_165849.jpg (786.35 KiB) Viewed 403 times
Mic output voltage.
Mic output voltage.
IMG_20140713_170017.jpg (894.19 KiB) Viewed 403 times

exceptdefeat
 
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Re: Is my MAX9814 mic shorted or damaged?

Post by exceptdefeat »

I should also mention the voltage is the same in quiet and loud conditions (playing music or no music). Also, I realize my soldering job probably isn't the best, but there are no visible bridges.

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Franklin97355
 
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Re: Is my MAX9814 mic shorted or damaged?

Post by Franklin97355 »

When you hook it up to headphones what happens?

exceptdefeat
 
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Re: Is my MAX9814 mic shorted or damaged?

Post by exceptdefeat »

I've never actually tried it. I don't have the headphone jack mentioned in the tutorial. I didn't think it was necessary and my project has no use for it.

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Franklin97355
 
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Re: Is my MAX9814 mic shorted or damaged?

Post by Franklin97355 »

Do you have another device to test your circuit and program then? I'm trying to figure out where that problem lies.

exceptdefeat
 
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Re: Is my MAX9814 mic shorted or damaged?

Post by exceptdefeat »

I actually just ordered a new one, in case there is a problem with this one. As far as my program goes, I don't think it's that relevant if the mic isn't outputting correctly. So I'm really just curious as to what the output voltage of the mic should look like if just reading it with a multimeter.

Could it be that the output changes too fast and the multimeter doesn't pick it up and just shows the mean voltage?

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adafruit_support_bill
 
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Re: Is my MAX9814 mic shorted or damaged?

Post by adafruit_support_bill »

A multimeter is not going to be able to follow the microphone output. Most multimeters average voltages over a fairly long interval (e.g. 1/2 second) so the audio waveforms are going to read fairly constant - regardless of the amplitude.

To verify correct operation of the device, it is best to follow the tutorial. Once you have verified that it is working correctly, you can start integrating it with your project.

exceptdefeat
 
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Re: Is my MAX9814 mic shorted or damaged?

Post by exceptdefeat »

Cool, that's sort of what I assumed, that the multimeter just wasn't sampling very often. Are you aware of any other ways for accurately sanity testing the device without using headphones?

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adafruit_support_bill
 
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Re: Is my MAX9814 mic shorted or damaged?

Post by adafruit_support_bill »

You could probe the output with an oscilloscope, but a set of inexpensive headphones can tell you what you need to know for a fraction of the cost.

exceptdefeat
 
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Re: Is my MAX9814 mic shorted or damaged?

Post by exceptdefeat »

Alright sounds good. I've got a buddy with an oscilloscope and maybe I'll check out the headphone adapter as well. Thanks for your help.

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