This is my first post on here and I am new to electronics, for I am a programmer and lack the knowledge of the electrical engineering.

With this is mind I have created a circuit to light a LED from the input of a mic element. The circuit works correctly for if the sound is soft or loud the brightness of the LED reflects it.

Problems:
- Since this circuit will eventually be running on batteries, and the batteries will lose voltage, the resistance set from the potentiometer will need to be constantly be readjusted.
- The LED does not get bright enough unless it is right in the mouth of the speaker.

Is there a better way of achieving this?
Thanks for your help.

Here is the circuit diagram-----

 

Put LED in series with the resistor, not across the transistor.

Don't know what kind of mike that is but some work could be done there as well.

 

You definitely need an amplifier feeding the transistor.

LEDs, 555s, Flashers, and Light Chasers

Chapter 12

 

Well if i run the LED in series with the 150 transistor it does the opposite effect. It is constant lit when sounds enters, it then dims. Was I supposed to run with the 10 resistor?

 

Depends on what you are after. Typically you want LED light with sound, but this isn't a must or a given. The amplitude of the signal from a mic is going to be small, so you need to increase it, and possibly make it variable gain.

 

Ok well the desired effect is to have it light with sounds so running across the resistor worked. What was the purpose of being in series with resistor?

 

I have looked at chapter 12 of the link provided. I see that that i should create the throbbing effect with the mic as the input to the 555? Also I am using 3 volts not 9 so would the resistance then be different?

 

You are referring to PWM. It doesn't have to use a 555 (see the RGB LED driver). PWM is good for large currents. I'd put your circuit as very comparable to the single transistor I put in there. For both you need a simple audio amp boosting the signal level (preferably with a volume control).

 

What drives volume besides the volume of the actual speaker. How can I amplify the output signal of this mic which is a 34H4S.

 

That is the million dollar question. There are quite a few options, I tend toward a class of chips called op amps. I'll have to get back with you with a schematic, assuming someone else doesn't beat me to it.

 

great! I appreciate your help.

 

Sorry I haven't gotten back with you. Between the job and DeMolay been busy last few days. I need to look up the specs for the mic your using, unless you're willing to use a speaker instead.

http://www.radioshack.com/product/index.jsp?productId=2062406&numProdsPerPage=60

 

Google has never heard of your 34H4S microphone. What type is it (electret or dynamic) and who makes it?

 

Sure the price on the speaker seems fine. The mic I am using is from my Dads collection from god knows when so the only info i can give you about it is what is engraved around it, which I have already provided. As far as i can see just from appearance it looks like a standard mic element. I guess it is so old it cant be found HA, which holds true then for most of my equipment unfortunately...

 

Nothing wrong with old equipment. The speaker I referenced could be any junk box speaker for this experiment.

The reason it matters is there are several different types of microphones, and they require different types of biasing. If you included a picture of the mic AG could probably give good advise on how to bias it. I tend to use magnetic types of microphones (which speakers can be considered a subclass of).

If you have a pile of parts let use know what you have, I can probably cobble something together schematic wise. Do you have a breadboard similar to the picture below, or are you soldering this together on a perfboard?

 

Yes i have a breadboard, also I have a multimeter, and I also have an oscilloscope. As far as materials I have a Radio shack right down the street if I'm missing something needed.

This is what my mic looks like. I will take a picture of mine if needed, but my camera is with a friend... Does this help?

 

A speaker, especially a cheap little one has a strong resonance that causes very poor sound when used as a microphone. A dynamic microphone also has a voice coil and magnet but does not have a strong resonance.

An electret mic is small, inexpensive and has excellent sound quality. It needs to be biased with 0.5mA to power its Jfet inside.

 

Ok so getting a electret mic will solve my brightness issue. Still I have this resistance problem. Hooked up to the breadboard of course has a constant voltage while if I were to power by battery they will soon start to spend their energy thus needing a readjustment of the pot to get resistance at the ideal lvl again.

 

Ok so getting a electret mic will solve my brightness issue.

Your LED is not bright because your mic is missing a preamp. Even an electret mic needs a preamp. You posted the photo of an electret mic. One pin connects to its metal case and should connect to the (-) of the battery. The other pin is the output signal that connects to the resistor that powers it and to the input of a preamp.

 

Ahh so that is what Mr.Marsden is designing the preamp. Yes i have looked up many circuits that amp but they don't seem they are designed for this simple circuit.