How to Reduce RF/EMI Noise in 3.7V MP3 Recorder With SD Card and Small Microphone?

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#1 21674367 26 Jun 2015 20:20

Andrew Feder Andrew Feder

Anonymous

Post #1
21674367 26 Jun 2015 20:20

i have an audio sampling device and both the microphone and the chip are picking up emi/rfi to the point where the audio is useless just high pitched noises , any ideas ? im using a 3.7v mp3 recorder that saves to sd with a small microphone
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#2 21674368 16 Jul 2015 22:34

Sambath Kumar Sambath Kumar

Anonymous

Post #2
21674368 16 Jul 2015 22:34

Hi,Andrew Feder,

Some solutions for your problem are given below,

1. Connect a22 ohms 2 watt resistor from your equipment ac power socket earth

terminal to the chassis of your equipment and connect the equipment chassis

to the dc negative supply of your power supply unit. The resistor acts as an

earth loop circuit dropping all the noise across it and preventing it from

entering your circuit.,also use a balanced in put connection for the mic .

2 . use transient voltage suppressor diodes (tvs diodes ) as per your voltage
requirement.
i am sure that your problem will be solved by point no 1 Regards Sambathkumar.
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#3 21674369 10 Aug 2015 09:20

Andrew Feder Andrew Feder

Anonymous

Post #3
21674369 10 Aug 2015 09:20

Hello , i greatly appreciatee your reply , this has basically eliminated the noise the pcb was picking up however the microphone is not balanced and is still picking up significant noise is there anyway i could make a balancing circuit with unbalanced output and input
#4 21674370 10 Aug 2015 12:03

Sambath Kumar Sambath Kumar

Anonymous

Post #4
21674370 10 Aug 2015 12:03

Hi Andrew Feder,

Provide a 0.1mf and a 10 mfd 25v cap parallel to your dc supply be careful of
the polarity of the 10 mfd cap while connecting it. try this first, afterwards you can go for the balancing circuit. hope you review my rating .

Thank you,

Regards V.Sambath kumar.
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#5 21674371 10 Aug 2015 12:42

Andrew Feder Andrew Feder

Anonymous

Post #5
21674371 10 Aug 2015 12:42

where would i review your assistance ? this is the recorder im using http://www.waytronic.com/voice_module_show.asp?/42.html , you wouldn't happen to have a diagram for a balancing circuit would you ? im going to go to my local electronics shop in the morning there closed to day unfortunately?
#6 21674372 11 Aug 2015 01:21

Sambath Kumar Sambath Kumar

Anonymous

Post #6
21674372 11 Aug 2015 01:21

Hi Andrew Feder,

I am sending one attachment this will clear all your problems.

pl check the attachment. Good luck.

Regards V.Sambath kumar
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#7 21674373 11 Aug 2015 02:04

Sambath Kumar Sambath Kumar

Anonymous

Post #7
21674373 11 Aug 2015 02:04

pl see the attachment .
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Topic summary

The discussion addresses EMI/RFI noise interference in a 3.7V MP3 recorder with an SD card and a small microphone, causing high-pitched audio noise. Solutions include connecting a 22-ohm 2-watt resistor between the AC power earth terminal and the equipment chassis, which is then connected to the DC negative supply to create an earth loop that reduces noise ingress. Using balanced input connections for the microphone is recommended, but since the microphone is unbalanced, adding a balancing circuit is suggested. Additional noise suppression involves placing a 0.1µF capacitor in parallel with a 10µF 25V electrolytic capacitor across the DC supply, observing correct polarity. A balancing circuit diagram was offered to assist in converting the unbalanced microphone output to balanced input, further mitigating noise. The specific device referenced is a Waytronic voice module recorder.
Summary generated by the language model.

How to Reduce RF/EMI Noise in 3.7V MP3 Recorder With SD Card and Small Microphone?

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Topic summary