Mic circuit(Can't make it work).

[Chris_p80]

Can i make a circuit (like a megaphone)
I tried two designs but didn't work
The components I used were
The mic ,a 0.5 watt speaker ,a BC 547(bc547C V1 E) transistor, a 10k and 100k resistor, a 104 ceramic capacitor and a 3.7v battery.

 

[tronitech]

The connections to the BC547 are shown incorrect. Check the datasheet for the BC547 but I think it should be CBE?

 

[Chris_p80]

I think also it's CBE.
I will turn it the other side and see!

 

[Chris_p80]

I think also it's CBE.
I will turn it the other side and see!

Quote:also made this no results (from chat gpt)

 

[Chris_p80]

The connections to the BC547 are shown incorrect. Check the datasheet for the BC547 but I think it should be CBE?

I made it like this still no luck

 

[AnalogKid]

That is a strange configuration for a mic preamp. Please post a link to the original circuit.

An electret microphone cartridge requires a DC bias current through it. Because your circuit has one end of the mic connected directly to a capacitor and nothing else, there cannot be a DC path through the mic.

No matter how many transistor connections you try, the circuit will not work.

ak

 

[Chris_p80]

That is a strange configuration for a mic preamp. Please post a link to the original circuit.

ak

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Is the link
(I was trying to make a circuit with a mic and a speaker ,a megaphone but this was the only one I found that didn't require a circuit board but it didn't work)

 

[Nigel Goodwin]

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(I was trying to make a circuit with a mic and a speaker ,a megaphone but this was the only one I found that didn't require a circuit board but it didn't work)

If there's just a silly picture, and no actual circuit (as in this case), it's a pretty good indication that the author doesn't have the slightest clue what he's doing, and it's never going to work.

You can't feed a speaker from a single small transistor fed from a microphone.

If you want a proper working electret mike preamp, refer to the opamp version on these forums here:

Basic opamp circuits

This question is asked repeatedly, and Audioguru always posts a really helpful graphic showing inverting and non-inverting opamp circuits for both single and dual supplies. So to avoid him doing this every time, I'm placing his graphic here, and making this thread 'sticky'. I've also uploaded...

www.electro-tech-online.com

You would then need a power amplifier to feed a speaker.

As an electret mike is omnidirectional, it's probably a poor choice for a megaphone anyway.

 

[Chris_p80]

Thank you for the information!!
I mean most of them don't work but I had hopes

 

[Ylli]

Trying to drive an 8 ohm speaker directly with the output of a small signal transistor? Will never work. Something closer to this might do the job for you.

 

[AnalogKid]

Chris:

Please give us more detail about what you want to achieve. If you want to build a megaphone from scratch, how loud does it need to be? Are you trying to be heard over 10 people at a pool party, or 200 people at a ball game?

Do you want to build the amplifier, or is buying an amplifier module off egay an option?

ak

 

[audioguru]

The mic preamp circuit you found is completely wrong.
A preamp drives a power amplifier that drives a speaker.
Here is a simple mic preamp circuit wired correctly:

 

[schmitt trigger]

Can i make a circuit (like a megaphone)
I tried two designs but didn't work
The components I used were
The mic ,a 0.5 watt speaker ,a BC 547(bc547C V1 E) transistor, a 10k and 100k resistor, a 104 ceramic capacitor and a 3.7v battery.

This is a prime example of web “how-to” circuits, which the author clearly did not ever built or tested.
Nor would he understand why it doesn’t work, either.

 

[ZipZapOuch]

This is a prime example of web “how-to” circuits, which the author clearly did not ever built or tested.
Nor would he understand why it doesn’t work, either.

But, the author had 58 visits to his website in the last 7-years.

 

[Nigel Goodwin]

But, the author had 58 visits to his website in the last 7-years.

Perhaps he checks on it every six weeks?

 

[ZipZapOuch]

The circuits are pretty painful over there...

Microphone circuit diagram - Electronics Help Care

This is the microphone circuit diagram. the maximum amplifier needs a microphone. without a microphone audio are nothing.

electronicshelpcare.net

 

[Nigel Goodwin]

The circuits are pretty painful over there...

That's the real problem, they aren't circuits at all, just a 'picture' of a bunch of components, obviously from someone who can't even draw a circuit, never mind know what one is.