Noise Detector

[audioguru]

You need to know the sensitivity of your microphone in your circuit (look on its datasheet) and the amount of gain of your circuit (calculate its gain) to determine the noise level in decebels.

Instead, you could borrow an accurate noise level meter and adjust your circuit to be the same which is called "callibration".

 

[corzy]

ok thanks for help me, can i use only use switch on/off because i only want to detect noisy in class only...can u help me???

 

[corzy]

i want to ask about value resistor 5K6....it 5600Ω or 56KΩ? and also value 2K2...it 2200Ω or 22KΩ???? help me please.....

 

[audioguru]

Some European people write 5K6 instead of 5.6k or 5600 because in "the good old days" a defective photo-copier missed printing the decimal dot.
2K2 is 2.2k or 2200. Philips ceramic capacitors have printed on them n47 instead of 0.47nF or 470pF. An Oriental 470pf capacitor is marked 471.

 

[deeps]

can i get d detailed explanation abt d circuit.

 

[audioguru]

can i get d detailed explanation abt d circuit.

You must understand simple opamp theory for you to understand the functions of the parts in the simple circuit.

 

[deeps]

atleast tell me y c3 is used?

 

[deeps]

i just uderstand rest of the circuit...i could also understand the way the amplifier works

 

[audioguru]

atleast tell me y c3 is used?

y? or Why?
R11 and C3 are a supply filter capacitor for the mic biasing and for the opamps.
Without C3 then when the LED turns on the supply voltage to the mic would drop and cause a POP sound at the input which would be amplified and make the LED light and the popping will be an oscillator.
All battery powered circuits need a supply bypass capacitor.

 

[gabriell]

Hello guys,

I would like to do this project and I want to simulate it first.
In Schematics, to simulate the microphone I chose the VPWL_FILE, and I attached a .csv file of a noise .wav file found on the internet converted like shown in the example: **broken link removed** but I get an error message <<Time not monotonically increasing in File "noise8bit.csv" Line 1>>.

The noise8bit.csv look is like this:
2,26757369614512E-05 0,2109375
4,53514739229025E-05 0,9296875
6,80272108843537E-05 -0,8359375
and so on....

Do you have any other suggestion for simulating the electret microphone using Schematics?
Or should I use Proteus (I have it but I didn't run any simulation with it, it will take some days to learn it) or another program?

One more thing... the IC1A Op-amp has both V- and V+ ping connected to the ground? and the second IC1B has the V- pin connected to ground and the V+ pin connected at (9-R11*Ir11) V?
Ir11 is the current that pass through the R11.

Best regards,
Gabriel

 

[audioguru]

I would like to do this project and I want to simulate it first.

Why simulate it? Most SIM programs do not know if they are coming or going just like the teachers.

One more thing... the IC1A Op-amp has both V- and V+ ping connected to the ground?

No.
R2 and r3 have equal values so their junction is at half the supply voltage. the op[amp has a very low input bias current so R4 applies half the supply voltage to the input of the opamp so its output can swing its max amount.

IC1B has the V- pin connected to ground

Its negative power supply pin is pin 4 which connects to ground. Its inverting input pin 6 connects to R8 and R10.

the V+ pin connected at (9-R11*Ir11) V?

Its + pin 8 is its positive power supply pin. Its non-inverting input pin 5 connects to the output pin 1 of the first opamp.

Ir11 is the current that pass through the R11.

The current in R1 is not important.

 

[Hero999]

He probably has to simulate it for his coursework.

I don't see a problem with it. Yes, simulators can be flaky but LTSpice is fairly reasonable. The only trouble is estimating the kind of waveform produced by the mic. I suggest you look at the datasheet for the mic for the voltage out vs the sound intensity and you should be able to devise a test to validate the different settings provided by SW1.

 

[gabriell]

Hello!

Wow, you were fast! Thanks for the explaining how the differential input works, and for the other comments.

I think there was a misunderstanding because I used the -V, +V labels instead of +Vs, -Vs (or +Vcc,-Vcc), for positive and negative power supply; I didn't meant voltage inputs of the op amp. Sorry! So in the circuit diagram, the -Vs pin is floating. If it's connected to ground that means that for the IC1A both -Vs and +Vs pin are connected to ground, is this possible?

Best regards!

 

[audioguru]

The negative power supply pin of the LM358 dual opamp is pin 4. The LM358 has both opamps inside and has 8 pins.The schematic clearly shows it connected to ground and to the negative terminal of the battery (not floating).
The schematic clearly shows only one positive battery, not an additional negative battery.

Please do not abreviate the positive supply (+Vs and the negative supply -Vs). The positive power supply pin 8 is not connected to ground and is not shorted to the negative power supply pin.

 

[gabriell]

Hi!

Thanks a lot for taking time to explain to a beginner! Now I understand! I can't wait to get the components and make this circuit. This will be my first one!

Kind regards!

 

[melkenneth]

Hi, may i ask, what do you mean by 330R by R13, as well as 560R by R7? D0es that mean 330 ohms and 560 ohms, respectively.? Thanks.

 

[ParkingLotLust]

Yes, 330R = 330 ohms and 560R = 560 ohms

 

[audioguru]

I wish Europeans would say "330 ohms" instead of "330R". Then everybody would know what they are talking about.
Some weird Europeans even write "4k7" instead of "4.7k ohms". Weird!

 

[melkenneth]

Thanks lotlust and audioguru. By the way, how will i c0nnect the mic.? Either side? I bought electret microphone, it has two terminals. Is that the needed device? Thanks!

 

[audioguru]

how will i c0nnect the mic.? Either side? I bought electret microphone, it has two terminals. Is that the needed device? Thanks!

The metal case of the electret mic is connected to the pin that should be the most negative voltage which is the junction of R2 and R3.
If the mic is connected backward then it might not work or will have a very low output.