How to interface a microphone to a speaker?

[scream_er]

Hey guys

Im a newbie in electronics. Im trying to learn step by step. Im not making a project or anything like that, just trying to learn. I want to know how you can connect a microphone in the simplest way. Can I directly connect microphone to speaker? Or do I need a circuit in between. If so can anyone point me out to a simple circuit that I can build and learn.

Thanks.

 

[xxtigerxx]

check this sites

Speaker Mic Circuit
Simple Microphone Preamplifier
Speaker Microphone | CircuitDiagram.Org

and also pdf it is good
**broken link removed**

 

[Pjdd]

screamer_er, just so there won't be any communication gap - please define what you mean by "speaker". Speaker is short for loudspeaker which, strictly speaking, is the component that converts electrical signals into sound (the technical term for a device that converts one form of energy to another form is 'transducer'). However, these days, particularly in the computer age, we often use the word 'speaker' for a combination amplifier-speaker set.

A microphone converts sound energy into very weak electrical currents (it's another type of transducer) and these currents are made stronger (amplified) with electronic circuits. The amplified electrical currents are again converted to sound by the speaker.

To answer your question: connecting a microphone directly to a speaker won't do any good because the electrical currents generated by the microphone are too weak to produce any useful sound at the speaker.

 

[yadavvlsi]

Electrical signals produced by a microphone are very weak. You need a audio amplifier which will increase the signal strength to drive a speaker.

 

[scream_er]

I am using an electret microphone and a cheap normal speaker and it doesnt have a model number or anything. It cost just $ 2.

Thanks

 

[Syncopator]

Removed by author.

 

[DartPlayer170]

I am using an electret microphone and a cheap normal speaker and it doesnt have a model number or anything. It cost just $ 2.

Thanks

You need an audio amplifier for two reasons:

1 - match the impedance of the microphone to the speaker's impedance
2 - amplify the voltage of the audio signal to a strength that will be audible from the speaker

You can check the impedance of the speaker with an ohm meter. It will likely be around 8 ohms. The meter will read slightly less ~ 7.2 ohms.
The impedance of the microphone will depend on the type.

 

[scream_er]

I have tried with the multimeter and found that the impedance of the speaker is 7.5 ohms and it is 0.5W. But i cudn't manage to find the impedance of microphone. Im using an electret microphone. So how can I find it?

1) After finding the impedance of both the microphone and speaker how can I match it?
2) To amplify the voltage of the of the microphone I will need an op-amp, right? Will LM358N do the job? Or any good alternative?

 

[DartPlayer170]

Put some music into the mic and measure the unloaded rms voltage out of the mic.
Then test with various resistors until the rms voltage drops in half. That will approx impedance of mic. If you are going to use an op amp, don't bother. Just design the op amp with a large input impedance, say 1 Mohm. Matching the input is only really beneficial with discrete transistor stages.

1 - design an amplifier with a preamp stage to match the impedance of the mic. You can have a larger input impedance if you want. If you use an op amp for example, there is no need to match the impedance since the op amp has plenty of gain. If you use discrete transistor stages though matching is more efficient and will create a better design.

2 - op amp is the simplest method. LM358 will work. It's a dual op amp package. You can use one for a preamp stage and the second with a pot for adjustable volume control. Then you will need a power amp stage to match the 8 ohm speaker.

 

[scream_er]

What I want to achieve is that, I want to connect the output from microphone to Microprocessor (arduino) and from microprocessor to speaker. So when I scream or whisper the microprocessor will detect the voltage and print out for me on the computer using serial monitor. And if the voltage is higher than a certain value it will on the speaker and output the voice. So, to achieve this I am using an electret microphone, a speaker with 8ohms and 0.5W and microprocessor (arduino uno). I would like to know how and what I should do to achieve this? Can you point me to a circuit or give me a simple block diagram to achieve this?

 

[DartPlayer170]

I haven't used Arduino before, but my plan would be to connect the mic to a pre-amp and the output of the pre-amp to the analog in of the Arduino.
The digital output of the Arduino would drive a DAC and then a power amp to drive the speaker. The rest is software. Possibly you will need an op amp stage in between the DAC and power amp but I would design the power amp and DAC first and then determine if a buffer is needed in between.