Hi,
I'm trying to create a simple circuit that controls LEDs through a microphone, NOT through an audio jack. This is similar to those LED rave shirts that respond to sound but I'd like to do it on a smaller scale and without a microcontroller if possible.

I'd like to create something similar to this:
http://www.instructables.com/id/Music-LED-Light-Box/

but instead of using an audio jack I'd like to use the electret microphone amplifier here: http://www.adafruit.com/products/1063#Downloads.

Basically have sound coming from the microphone, driving the transistor to control the LEDs powered by a battery. Will this work? Or will I need a microcontroller. Any help is appreciated all the projects I've found use an audio jack and/or require a microcontroller

 

Hi,
I'm trying to create a simple circuit that controls LEDs through a microphone, NOT through an audio jack. This is similar to those LED rave shirts that respond to sound but I'd like to do it on a smaller scale and without a microcontroller if possible.

I'd like to create something similar to this:
http://www.instructables.com/id/Music-LED-Light-Box/

but instead of using an audio jack I'd like to use the electret microphone amplifier here: http://www.adafruit.com/products/1063#Downloads.

Basically have sound coming from the microphone, driving the transistor to control the LEDs powered by a battery. Will this work? Or will I need a microcontroller. Any help is appreciated all the projects I've found use an audio jack and/or require a microcontroller

Welcome to the forum!

The mic/preamp you posted is will work fine. It appears to need a 5 volt max supply which can be supplied
by a simple voltage regulator.

But, not surprisingly, the instructable has some issues.
The LED's should not be connected directly to the 12vdc power supply
without a current limiting resistor.

The transistor must also have at the very least a current limiting resistor and capacitor between the base of the transistor and the signal from the preamp.

I'm out of time for now, but this is the place for excellent help, just ask !

EDIT: This circuit responds to overall audio volume. Much more can be done with additional circuits and LED's.

 

The transistor must also have at the very least a current limiting resistor and capacitor between the base of the transistor and the signal from the preamp.

.

Thanks! thats what I was thinking. so would a 300 ohm resistor and a 100uF capacitor be enough for 6 LEDs?

Also would you recommend I use a D cell battery or a 9 Volt to get the most number of LEDs out of my circuit

 

The capacitor and resistor would work to connect the preamp to the transistor base.Then later add a volume pot between.
Did you calculate those values ?

You still also need current limiting for the LED'S
Read this great info on using LED's from this site.
http://forum.allaboutcircuits.com/blog.php?bt=674

How long do you want this to run at a given time?
Depending on that, batteries could be fine if you use efficient LED's

What parts if any, do you already have ?
How many LED's do want to use. Because a darlington transistor might be better. You could make one using two of the transistors listed.

 

The capacitor and resistor would work to connect the preamp to the transistor base.Then later add a volume pot between.
Did you calculate those values ?

You still also need current limiting for the LED'S
Read this great info on using LED's from this site.
http://forum.allaboutcircuits.com/blog.php?bt=674

How long do you want this to run at a given time?
Depending on that, batteries could be fine if you use efficient LED's

What parts if any, do you already have ?
How many LED's do want to use. Because a darlington transistor might be better. You could make one using two of the transistors listed.

Thanks! I hadn't thought about doing the circuit with two transistors.

Ideally, I would like this to last on a battery for 4-5 hours and contain at LEAST 6 LEDs.

If you don't mind explaining, how would I use the two transistors instead of just using one to control the LEDs. And by volume pot, I'm assuming you mean just a normal 10k potentiometer, correct?

I currently have the resistors and the LEDs. I'm hoping to complete this project before August ends so I have time to order whatever I need.

 

...
I currently have the resistors and the LEDs. I'm hoping to complete this project before August ends so I have time to order whatever I need.

Did you look at the info on LED's ?

What are the specs for your LED's ?
Need the Vf (forward voltage) and the max current.

What value and wattage resistors do you have. (I know you mentioned 300 ohm resistors.)

The exact part numbers, values etc are needed to give you proper guidance.

 

Did you look at the info on LED's ?

What are the specs for your LED's ?
Need the Vf (forward voltage) and the max current.

What value and wattage resistors do you have. (I know you mentioned 300 ohm resistors.)

The exact part numbers, values etc are needed to give you proper guidance.

These were the LEDs I bought a while back from amazon. http://www.amazon.com/microtivity-I...1?ie=UTF8&qid=1376238670&sr=8-1&keywords=LEDs

So the forward voltages of the ones I'm working with are 1.9-2V for most of them but I'd like to use the LEDs that have Vf of 3V if possible.

As for the resistors, they are all 1/4W and I have these available to me (I can always buy others if needed): 100, 150, 200, 220, 270, 330, 470, 510, 1k, 2k, 2.2k, 3.3k, 4.7k, 5.1k, 6.8k, 10k, 20k,

Also would I still be using the tip31 transistor?

Thanks again for the help

 

Have to go, back later, so quickly:

May not need the TIP transistor. The supplier for the preamp has 10 pack 2n2222's, I would suggest getting those.

Using a 4.8 volt battery supply would make life easy. But then 3 volt-ish LED's would need to be paralleled each with it's own current limiting resistor.

2 volt-ish LED's could just possibly be used in strings of two with 1 current limiting resistor.

We still don't know the max current rating for the LED's you have.
Guessing that it is 20 ma is a start, but it can be determined with resistors, battery and voltmeter.

Do you have a voltmeter?

EDIT: Volt-ish is a highly technical term

 

yes i have a volt meter

 

Need to decide on a power source. For simplicity a 4.8 volt battery would be good.

Check the brightness of the LED's with a DC voltage and a series resistor. See the link I posted earlier.

The resistor value is calculated using the LED voltage drop, DC voltage supply, and current supplied to the LED. Many small LED's have a max current of 20-30ma's. You should run them at less, only what's need for acceptable brightness.

The resistor formula is:
(DC supply voltage - LED voltage)/LED current(amps)

Let's assume a 4.8 VDC supply. (current as required)
Lets start with a 3.2 volt LED, and a LED current of 0.010 amps(10 ma's)

So,
(4.8 volts DC - 3.2 LED volts)/.010 amps =
1.6 volts /.010 amps =
= 160 ohms

Use the closest standard value resistor.
Experiment with different resistor values, but don't exceed 20 ma's or so.

 

Thank you so much for the help! I'll let you know how it goes

 

Happy to help - good luck !