Sound Reactive/Alternating LED

Discussion in 'The Projects Forum' started by IronMod, Jun 14, 2011.

  1. IronMod

    Thread Starter New Member

    Jun 14, 2011
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    I am trying to make a project for my apartment where LED's will be sound reactive as well as alternating. I have searched through here and found lots of threads on alternating LED's, but didnt see one where the two where put together. If theres a thread, please let me know and I will use that for reference instead. I'll be using around 200 LED's. Most likely Blue, Red, and White. I plan on using the LM386N for the sound reactive part and have used them before with good results. Through reading the threads on here, it sounds like I should go with the 555. My question is can i use them to make an alternating LED circuit, and then just use the output from the 555 to the power input of the LMN386N to have them still be sound reactive? I'm worried if I put the LMN before the 555, that it will mess with the 555 being able to alternate. I know the output of the LMN is 3 volts and stays current, so would it still be ok?

    I was also wondering if I could completely bypass the having to use both and maybe do this all with a 4017? Or if its really possible, use the 4017 to make an alternating pattern that is also sound reactive using the LM386N.

    Sorry if this doesn't make sense, I'll try to clarify more if needed. Thanks for any help!
     
  2. KJ6EAD

    Senior Member

    Apr 30, 2011
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    363
    I can't think of a way that the 4017 would apply. Feed the output of the LM386 into the control voltage input of the 555 in pulse width modulation (PWM) configuration or pulse position modulation (PPM) configuration, whichever gives the most pleasing effect. You will have to scale the amplifier output correctly for the 555 and set the running frequency of the 555 fairly low (below 40 Hz).
    http://www.fairchildsemi.com/ds/LM/LM555.pdf (Pages 8 & 9)
     
  3. IronMod

    Thread Starter New Member

    Jun 14, 2011
    15
    3
    Thanks! That makes total sense. Guess all I can do now is try it and see
     
  4. IronMod

    Thread Starter New Member

    Jun 14, 2011
    15
    3
    Ok so I'm a little confused, but after going through a few threads on here, this is what i have come up with, My question is are my resistor and capacitor values right? I have it set for 35hz at .02 seconds. I plan on using 6 white LED"s and 8 Blue LED's, 1 555 1 386. I want it to go from blue to white blue to white etc. Do I need a transistor? I'm still a little confused. I also have an extra 386 and 555 on hand if I need it. Thanks a bunch. Heres what i've come up with as far as a schematic. I already have the 386 installed so I know thats working right, its the 555 im confused on. Thanks a bunch. Oh, I also will be using a 5.9v 350mA power source. But I also have a 3v 200mA as well.
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    Couple of questions. You are using the simplest mode of the LM386, max gain, basic power supply connections. Is this what you are after?

    You don't truly show your microphone source, it is very important. An electret mic won't work like that, for example. A dynamic mic would however, or even a simple speaker.

    Resistors for LEDs (and one resistor per LED chain, or 3 resistors) are not optional, you have blown either the 555 or the LEDs or both if that were an accurate schematic.

    You also need a full range of bypass caps for a circuit like this. The tendency to oscillate will be very high other wise. Don't forget pin 5 of the 555.

    Decoupling or Bypass Capacitors, Why?

    LEDs, 555s, Flashers, and Light Chasers
     
  6. IronMod

    Thread Starter New Member

    Jun 14, 2011
    15
    3
    The only reason I didn't put resistors on the LED's were because I though the voltage coming out of the 555 would 3 volts with 5 volts in. Sorry about the schematic, I'm still in engineering school and there is still such a ton I have to learn before anything I design can be accurate. I still have a few questions about the diagrams in the Leds, 555s, article.

    I got to chapter 8 and it seemed like the circuit I want, except this is for 4, I only want to go between blue and white, so would I just take the top 2 555's, keep d9 and d15, and build it like that? Or did I miss something previously on how to do just 2? From what I read, the others were just for either 1 color or having more than on color on one pattern. But in that diagram, pin 5 isn't used at all, is that because its just kind of a "common knowledge" that pin 5 needs to be grounded with a .01 uf cap? I also saw you said putting them in parallel is a bad idea, something I actually didn't know. I always though series was bad just because it hogs more current. So I should do these in series correct?

    Other question is the 386 takes the current and puts it in half as I know you already know, so with a 3 volt source, its only 1.5 v out feeding into the 555, and the 555 needs 4.5v for operation correct? So then I would need a bigger power source? And my sound source is just a speaker from my home reciever. And as far as what im doing with the 386 is the basic control of it. I already have it hooked up and it has been working. All im doing right now is making LED's under my computer monitor beat to the music, but now I want them to beat to the music and alternate between colors while doing it. This is all leading up to a bigger project but I wanted to start small.

    Thanks alot for the help, I have read alot of your threads and I know you end up answering alot of the same questions multiple times so sorry if I'm doing that, I just cant seem to find someone who did a 386 and 555 together and posted any info on them.
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    Thing about LEDs, they can not regulate current, but they are current controlled devices. So the resistor is needed. It is one of the reasons I wrote the LEDs, 555s, Flashers, and Light Chasers article.

    Check out chapter 12 of the article, it has some alternate ideas you might be able to use.

    You could use a CMOS 555. In spite of everything I've said at 3V (it will go down to 2V, and may work at 1.5VDC). At such low voltage the TLC555 (sold by Radio Shack) only gives a little current out, in other words it can substitute for the resistor. You can drop the batteries to 3.0V (2X AA or AAA). Actually to do this you have to.

    The 555 Projects

    CMOS 555 Long Duration Minimum Parts LED Flasher

    As for answering the same question over and over, there is no problem with that. People aren't born knowing this stuff, someone taught me, I teach you, someday you'll have something to teach. It all passes forward. The only dumb question is when you don't ask it.
     
  8. IronMod

    Thread Starter New Member

    Jun 14, 2011
    15
    3
    I think you've actually cleared up most of what I'm confused on. The only question I have is the voltage in the same as the voltage out for the 555 at such low voltage? I saw you mention so someone else in another article running these at 12 volts gives you a 10 volt output I think is what it was, unless you were talking about something else.

    I would rather use this off a 3 A/C adapter because I already have it wired to the spot where I want, then I would need the .01 uf cap on pin 5 right? I saw you say that you dont need it if your using a battery.
     
  9. Wendy

    Moderator

    Mar 24, 2008
    20,764
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    A CMOS 555 is quite different than a 555. A standard 555 had a high current output, always, while a CMOS 555 the output current is quite limited, and the lower the power supply voltage the less current drive.

    Check out these threads, pay special attention to the Theory of Operations.

    555 Schmitt Trigger

    555 Hysteretic Oscillator

    The Darlington Pair transistor output has some implications for a standard 555. It allows for high current output, even at the lowest power supply level, but it will drop a minimum of 1.2V. This always has to be allowed for.

    A CMOS chip can't provide much current, but it goes rail to rail. In other words it goes from one power supply to the other power supply on the output.

    A CMOS 555 and a standard 555 are quite different animals. Something to remember when using them. Don't get confused which part is which. They are not always interchangeable.
     
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