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Author Topic: Working on A Small Project of Building An External Mic for A iPhone  (Read 1660 times)

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Autamay

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• OS: Windows 7
Working on A Small Project of Building An External Mic for A iPhone
« on: October 23, 2017, 04:06:25 AM »
I am working for a while now on a small project of building an external mic for the iPhone to be hooked in parallel to headphones (via the 3.5 mm jack). Basically, I want to replace the iPhone's original headset microphone with another microphone, but still use the headphones to listen.
Below is an image of the prototype structure (based on 2 existing products, but it is actually not working; probably due to impedance issue):

Some clarifications on the image:
item #5 - split point between microphone jack and headphones jack. item #4 - iPhone plug 3.5 mm item #3 - a microphone which for now is NOT working since the iPhone seems NOT to identify it (probably impedance issues - it's impedance about is about 650 Ohm) item #2 - simple headphones jack (any headphones with 3.5 mm plug can hook there) item #1 - microphone jack hooked to the external microphone I have for now. I would like to focus my question on the electrical aspects of my project for now. Known data I gathered so far (please feel free to correct any mistake you identify):
iPhone supply's 1.5 V on the TRRS 3.5 mm jack. the TRRS plug of iPhone is built of from 4 pins: Left/Right/Ground/Mic Questions:

DaveLembke

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Re: Working on A Small Project of Building An External Mic for A iPhone
« Reply #1 on: October 23, 2017, 02:56:56 PM »
You could calculate your current for each device by I = V/R voltage at 1.5 Volts, what is your Resistance R if its 3 Ohms at 1.5 volts then I = Current = .5 Amps ( aka 500mA ). Then add up the draw of the devices and then you know.

SO

I = V/R

IS for example

.5 = 1.5/3