A local HAM has asked me help to integrate a microphone module in his mobile setup. He was directed to the little MEMS/silicone microphone module shown in the picture below with very positive comments.
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| MEMS microphone with amplifier circuit. |
The problem with his initial setup was a wiring error in the RJ plug, but with that fixed the module showed an unexpected effect: even in complete silence the circuit would produce a strong hiss like driving at 100 km/h with open windows, and the modulation was extremely loud.
Digging a bit further on aliexpress I found a description of the circuit:
- Working voltage: DC3V-5V
- Output about 30mw, can directly drive ordinary 32 ohm headphones
- R5: amplification adjustment resistor, resistance value can be used 4.7k-100k [cut] The higher the resistance value, the higher the gain [the board comes with 22k]
- R6: for the microphone sensitivity adjustment resistor, shipping default for high sensitivity (resistance value of 0 ohms), the resistance can be selected from 0 ohms -10K between [cut], the greater the resistance value of the resistor, the lower the sensitivity
Very good information: the stock board has maximum microphone gain and middle amplification gain.
I also checked some random datasheets from Knowles SiSonic product range and noticed that 5V is usually the Absolute Maximum Rating for their MEMS microphones.
He gave me one module to experiment with. Stay tuned!
