need help with LED project using electret microphone

Discussion in 'The Projects Forum' started by knaa, Aug 9, 2013.

  1. knaa

    Thread Starter New Member

    Aug 9, 2013
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    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 :D all the projects I've found use an audio jack and/or require a microcontroller
     
  2. tubeguy

    Well-Known Member

    Nov 3, 2012
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    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.
     
    Last edited: Aug 9, 2013
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  3. knaa

    Thread Starter New Member

    Aug 9, 2013
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    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
     
  4. tubeguy

    Well-Known Member

    Nov 3, 2012
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    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.
     
    Last edited: Aug 10, 2013
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  5. knaa

    Thread Starter New Member

    Aug 9, 2013
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    Thanks!:D 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.
     
  6. tubeguy

    Well-Known Member

    Nov 3, 2012
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    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. :)
     
    Last edited: Aug 11, 2013
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  7. knaa

    Thread Starter New Member

    Aug 9, 2013
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    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 :D:D:D
     
  8. tubeguy

    Well-Known Member

    Nov 3, 2012
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    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 :rolleyes:
     
    Last edited: Aug 11, 2013
  9. knaa

    Thread Starter New Member

    Aug 9, 2013
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    yes i have a volt meter
     
  10. tubeguy

    Well-Known Member

    Nov 3, 2012
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    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.
     
    Last edited: Aug 11, 2013
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  11. knaa

    Thread Starter New Member

    Aug 9, 2013
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    Thank you so much for the help! I'll let you know how it goes
     
  12. tubeguy

    Well-Known Member

    Nov 3, 2012
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    Happy to help - good luck !
     
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