Need help to create LED circuit with microphone signal receiver

[shovs]

Hello guys! My name is Elvijs and I just joined to this forum to seek your help in creating one of my ideas into reality..
My idea is to create a microphone signal receiver who could receive signals (music) from the area where it is located (a room preferably) and transfer signal to LED circuit, so the LED's would go together with music wirelessly. I've searched this forum, found something similar, but not the thing what I need..
Mic should work when it hears music waves in the room and in the same moment light up the LED's. In the LED circuit there will be about 80 LED's. Microphone should be sensitive to pick up quiet noises (amplifier) or something that would let the circuit work properly.
So now, I'm here to seek help from the people who have experience in electronics, because I have almost none.
Thanks for every answer there will be!

This schematic was designed by a electronics professor whom I asked for a little help. This far I have managed to get, but this is not enough. Maybe you can tell me if there is some mistakes or something bad in the scheme, because he said this schematic is from a long time ago when he made light music..

 

[MikeMl]

The circuit appears to have a preamp for an electret mic, a limiter (automatic gain control), more amplification, and then a very crude filtering circuit which lights three leds corresponding to three frequency bands.

How many frequencies are you trying to get? If 80, then the frequency selective filters and led drivers will have to be much more complex... (thousands of parts).

Perhaps there is a better approach?

 

[cowboybob]

Welcome to ETO, shovs!

Do you want the LEDs to respond to the volume of the music or the frequency of of the musical tones (as the circuit you posted implies)?

A multiple LED circuit that responds to the volume of the music (a VU meter: see below) is relatively simple. As MikeMI notes, a circuit that responds to the various frequencies of the music is considerably more complex.

Here's an example VU meter (IC1 is and LM 3915). Only 10 LEDs used - 80 LEDs sounds a bit extravagant...
**broken link removed**
Some minor adjustments to the circuit would be needed to accommodate the electret microphone. The voltage regulator circuit (IC2) might not be needed.

 

[shovs]

Hello, MikeMI!
The thing is, we could use only one frequency (bass for example), but the thing is that we need a circuit that will pick up even quiet noises( if the music is quiet, the thing still would run).
I believe that there are a lot of better approaches, but I need to find the right one, and as it is, I have no idea what to look for..

Hello cowboybob!
I want LED's to respond to the frequency of the music (for example a bass or kick). Project is extravagant mate I want to build a completely new invention/product for people who love music and design. Only what I can afford from the circuit is that there is only wires going to electricity plug. I want it to be completely wireless(except the electricity wires). That's why I need to use the microphone in the circuit.. I'm having a hard time to figure out how the mic could pick up the quiet noises in the room and light up the LED's?!
Perhaps I need a specific mic (powerful), specific circuit that could run the thing smoothly..

I'm really thankful for your answers, every detail of your words count! Thanks!

 

[audioguru]

Frequency is the pitch of a sound. Level is the loudness of a sound. A bass beat or drum beat is a loud low frequency sound. A circuit that picks up and displays a drum beat probably won't show high frequency chhh, ch, ch, chhh, ch, ch, chhh sounds.

A microphone has a low output level. It uses a preamp circuit to boost its level so that an LM3915 or LM3916 can display it.
An LM3915 has a range of 30dB which is from faint to average or from average to loud. The datasheet shows how to connect two LM3915 ICs so they show a range of 60dB which is from faint to loud.

 

[shovs]

Hello, audioguru! Thanks for your answer, it explained some things
You mentioned in your answer about datasheet - what datasheet mate?

 

[cowboybob]

For instance:

http://datasheetcatalog.com/datasheets_pdf/L/M/3/9/LM3915.shtml

Datasheets contain quite a bit of information: note figure 39 in the above link.

Keep in mind, shovs, that the device you intend to make (a multiple frequency input sensitive, low signal strength LED bar graph) is not going to be a simple task.

The more I think about it, I would suggest getting your feet wet by starting with a single frequency detector circuit (perhaps using an LM567, a VERY handy and simple tone decoder device) for this purpose and using its output to trigger an LED. I have used the devices and, believe me, they make the easiest, single frequency detector circuits that I have ever made and used, They can be configured for use (one at a time) across the entire audio range:

http://pdf1.alldatasheet.com/datasheet-pdf/view/8984/NSC/LM567.html

And an audio signal can be fed, simultaneously, to as many cascaded LM567s as you choose.

 

[cowboybob]

<EDIT> of course, a μC (e.g., an Arduino, etc.) could also be used if tighter band-widths were needed.

 

[audioguru]

I think Texas Instruments improved the original datasheet from National Semi now that TI has purchased National. I will add the TI datasheet to my collection.

 

[shovs]

Hello guys and thanks for your answers!
I'm gonna try to get my hands on that LM567, because in my town I couldn't find this component. I'll need to order that and it will take some time :/
About that Arduino.. Would it be easier to make a circuit with it or with LM567?

 

[cowboybob]

The LM567 circuit(s) would be simpler, cheaper and more expandable than the Arduino system.

The Arduino system would be more "tunable" (frequency accurate) but more expensive, more difficult to expand (additional I/O ports) and would, of course, have to be programmed.

Remember, you'll need 1 (one) LM567 for each tone (frequency) you wish to "capture". Note the bandwidth formula on the datasheet.

 

[audioguru]

I think instead of using many LM567 tone decoders, you simply need bass, midrange and highs in a circuit driving the LEDs. Bass would cover frequencies from 20Hz to 300Hz, mids would be 300Hz to 3kHz and highs would be 3kHz to 20kHz.
Look in Google for Color Organ circuit.
Each of the the bass, mids and highs filters would drive an LM3915 IC that drives 10 or 20 LEDs each.

 

[ronv]

What is it that you don't like about your circuit? Does the music need to be to loud or what?

 

[Reloadron]

The circuit you posted is most commonly referred to as a color organ and it works just as Mike covered. Color organ circuits can be found to operate off the AC line and drive incandescent lamps or many designs are low voltage and will drive LEDs. Typically the basic versions will respond to bass, midrange and treble frequencies and each frequency range is called a channel. The more channels, as Mike points out, the more parts and the more effort to have better filters. Many have a single master gain control and then individual gain controls for each channel. A Google of "Color Organ Circuit Schematic" will get you literally dozens and dozens of circuits, some more complex than others. I saw mention of wireless which could be worked into the scheme. Again, a good basic starting point is color organ circuit.

Also, per ronv what do you not like about the circuit the professor gave you. It should work.

Ron

 

[shovs]

Hi guys, thanks for answers, I'm starting to understand a lot more about the way I should go!
The circuit that professor gave me - works, but.. The thing is that it works only then, when I put music source (for ex. a telephone playing music) directly to microphone's head.. I need the circuit to pick up sounds from at least 3m range. Of course if I put music loud, like really loud, it picks the signal up, but if the music is on low volume - nothing..
Color organ circuit is something similar to what I want to build, but not exactly that..

 

[audioguru]

Your professor's circuit has an electret mic feeding two opamps having a total gain of 121 times which is not much gain for a microphone. The automatic gain control (the Q1 transistor) might reduce the gain even more.
Try eliminating the automatic gain control by shorting the base of Q1 to ground to see if the sensitivity improves.

I have a VU meter that shows the levels of sounds in my family room. Its maximum gain is 1820 times which is 15 times more than yours. It shows whispers anywhere in the room.

You can increase the gain of the professor's circuit by increasing the resistance of R5 and R10. Try 220k each then the total gain will be 529 times, then increase these resistors to 330k each and the total gain will be 1156 times, then increase these resistors to 390k each and the total gain will be 1600 times.

 

[shovs]

Hi audioguru!
Mate if this is gonna work, that would be excellent! I'm gonna try that asap.
Lately I came up with a different variation for my project. What if I would use wireless signal transmitter + receiver?
Transmitter could be built into a little flash cartridge like USB mouses do and receiver built into the circuit together with bass signal pickup thing. If I would somehow program the transmitter to transmit only for example bass from any music source on the computer and receiver would light up the LED's in the same time within 10m radius, could it possibly work?

I appreciate your effort for answering me! Cheers!

 

[audioguru]

It is very simple to design a circuit that cuts high frequencies but passes bass frequencies. A series capacitor feeding a resistor to ground does it (R13 and C10 in the professor's circuit). Add a transistor or opamp and the filter will have a sharper slope.

 

[shovs]

Ok, mate, but what about that receiver/transmitter? How do you think?

 

[audioguru]

My wife is my mate and I am not a pirate nor fisherman, MATE! G'day, are you in down under?

You can design and build or find a receiver/transmitter if you want. You could use infrared light instead of radio signals. It is simpler to use a microphone like I do. My circuit picks up any sound in the room and in the next room.