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Building a Microphone should be easy, right?

Braeden Hamson

Feb 18, 2016
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I'm probably not on the right forum right now. But hey one of you might know.

I wanted to build my own microphone so I pulled the mic out of some crappy IEM headphones and soldered one up with a mono jack. The trouble is my PC doesn't see it as a microphone. And I have no idea why (Electronics Hobbyist Motto "But that should work!") I am using the correct splitter to take the two jacks of the headphones and mic and convert it to the 4 connector type that my ASUS laptop supports.

Is it because the mic has the wrong number of ohms? I'm running out of ideas. I don't want to admit defeat and pick up some $20 mic.
 

Harald Kapp

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There are different kinds of microphones, but you're of course aware of that, aren't you?
What kind of mic is the one you use?
Assuming that it worked in the headset before, I see two possibilities:
  1. you soldered it to the wrong pins of the connector.
  2. you destroyed the mic during the removal from the headset.
What pinout did you use?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Or the level out of the mic is so low that it won't work with your PC's sound card.
 

Braeden Hamson

Feb 18, 2016
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Harald
I forgot to mention that my laptops built in mic is on when the mic is plugged in, and that my pc thinks the mic is a speaker. So I suppose I'm using the wrong kind of mic.

Ramussons

That's probably the issue. Is there a way I can tell the difference?
 

duke37

Jan 9, 2011
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Wikipedia gives details of how a ribbon microphone is constructed. That would be quite a project.
 

Harald Kapp

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my pc thinks the mic is a speaker.
You're using the right input, sure you do?
You can tell the difference between a capacitor based microphone and a coil based by microphone by measuring the resistance of the mic. A capacitive mic has a very high (~infinite) resistance, a coil based mic has a comparatively low resistance.
You can try to put a capacitor (e.g. 100 nF) in series with the microphone. This will block DC, so the mic should not be 'recognized' as speaker, bur will allow AC to pass.
 

Braeden Hamson

Feb 18, 2016
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Thanks Harald
Any recommendations on the value of that capacitor? And out if curiosity what would the different values do in the circuit. Haha using a capacitor in an AC circuit raises a lot of questions, what would a capacitor do in an AC circuit?
 

Audioguru

Sep 24, 2016
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If you plug into a microphone input then the built-in microphone should be disconnected by the jack.
A microphone input jack on a laptop has nothing to do with a speaker. Maybe the symbol for a coil mic looks like a speaker to you? A coil mic is called a "dynamic" mic. Look up what type of mic in the laptop's operating instructions.

A capacitor mic is different. A laptop is usually designed for a "electret" mic that is a capacitor mic with a built-in Jfet impedance converter. The Laptop applies DC power in the mic wires to power the Jfet. If the mic does not work then you probably have its two wires connected with backwards polarity. Reverse them.

Edit: You used a mono jack? Instead maybe you used a mono plug? Then maybe is for headphones without the mic contact on it.
 

Braeden Hamson

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Audioguru
Well you sound like the right person. If only my laptop had dedicated ports for mic and audio. Instead I have a CTIA 4 connector combined headphone/microphone port. Electret mic eh? I had no clue mics were so complex.
 

Audioguru

Sep 24, 2016
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Your mono plug is shorting the mic connections on the plug. Get a 4-connections plug. I found this schematic of a 4-connections headphones plug in Google:
 

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Braeden Hamson

Feb 18, 2016
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I've got one of those it works for my plug. It's wired like that one you've listed.
I've also flipped the polarity on my mic a few times, no dice.
 

Audioguru

Sep 24, 2016
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I have a few electret mics from cell phones and child's toys and they all work fine. Maybe you have the extremely tiny mic from the cord of a headset? It is very difficult to make connections to it.
 

Braeden Hamson

Feb 18, 2016
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I'm using a 3.5 mm mono plug. Ain't no hotdog down a hall way. My circuit is two wires, a mic and a plug. I think I'll dig a mic out of an old phone. So do these mics in the phones have all the supporting hardwaee built into their cases or is it on the board next to it?
 

Audioguru

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A mono plug shorts the mic terminals in the 4-wires jack. You need a 4-wires plug for your electret mic.
You need a 2-wires electret mic. Some electret mics have 3-wires. Connect the mic to the plug with shielded audio cable, not 2 wires that will be antennas that pickup hum from mains electricity wiring all around you.
Here is what a 2-wires electret mic looks like:
 

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Braeden Hamson

Feb 18, 2016
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Perhaps I should've been more clear. I'm using an appropriate spitter, 4 contact plug two ports one for audio out one for in.
And if case grounding is the way to know if something is an electret then I have an electret. Mind you I pulled this mic out if a pair of ear buds, with inline mic.
 

daberbaber

Feb 2, 2012
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After reading through this thread, I believe the plug and subsequent wiring to be the problem if the proper mic is being used.
 

Braeden Hamson

Feb 18, 2016
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After reading through this thread, I believe the plug and subsequent wiring to be the problem if the proper mic is being used.
Hahaha, your very correct. I just got it working last night, the mono plug on the splitter wasn't playing ball. So I chopped it off and put my own on. Works now.
 
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