LED organ

Discussion in 'The Projects Forum' started by Rocky_circuits, Nov 11, 2011.

  1. Rocky_circuits

    Thread Starter Member

    Nov 1, 2011
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  2. SgtWookie

    Expert

    Jul 17, 2007
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    That IC is a quad opamp.
    IC1 is one part.
    IC1A is one operational amplifier inside of IC1.
    IC1D is another operational amplifier inside of IC1.

    Does that make sense now?
     
  3. Rocky_circuits

    Thread Starter Member

    Nov 1, 2011
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    Yep. Just to be clear, that means IC1D is no different from say IC1B if I happened to swap their places on the circuit.

    Last question. Probably obvious but to be sure, The virtual ground has a V-ground out. That just means put all the other virtual grounds to that one right?
     
  4. t06afre

    AAC Fanatic!

    May 11, 2009
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    In this case all the 4 opamps in the IC are identical. So you can order/use then in any order you prefer. Then I make PCBs. I quite often swap internal parts to make the layout more easy.
     
  5. nerdegutta

    Moderator

    Dec 15, 2009
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    Isn't this a DIL 14 IC? As in one IC, containing IC1A-IC1D?
     
  6. Audioguru

    New Member

    Dec 20, 2007
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    Yes, connect all V-ground points together.

    Note that the opamp making the V-ground is not needed since the (+) inputs of the opamps use extremely low current. Remove the V-ground opamp and connect the V-ground points to the junction of the two 100k resistors and C15 at its input.
     
  7. Rocky_circuits

    Thread Starter Member

    Nov 1, 2011
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    Interesting.. I wonder why he bothered including the V-ground op amp then. My TA said it looked like a voltage divider at first glance.

    So I did build everything... but It doesn't work sadly. The red LED's are always on, the yellows seemed to work as far as I could tell.. I couldn't tell if it was pulsing simply to anything audio though. The blue's just didn't work at all.
    Even with that, the LED's were verrrry dim. Through a bit of testing I found that around .8 volts was constantly being sent out to the transistor so it was somewhat on the whole time. It turns on officially at 1 volt (very brightly might I add)

    I think I'll try and rebuild it. I have nooo idea what I did wrong.. I've looked over it over and over but everything appears to be correct.
     
  8. Audioguru

    New Member

    Dec 20, 2007
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    Of course the V-ground is a voltage divider. It has a voltage divider at its input made with two 100k resistors in series from 12V to ground. The V-ground opamp boosts the current but it feeds almost no current to the (+) inputs of the filter opamps. So the two resistors and the filter capacitor are all that is needed to make the V-ground =6V.

    So I did build everything... but It doesn't work sadly. The red LED's are always on, the yellows seemed to work as far as I could tell.. I couldn't tell if it was pulsing simply to anything audio though. The blue's just didn't work at all.
    Even with that, the LED's were verrrry dim. Through a bit of testing I found that around .8 volts was constantly being sent out to the transistor so it was somewhat on the whole time. It turns on officially at 1 volt (very brightly might I add)[/quote]
    The base of each transistor has a 100k resistor to ground which turns off each transistor when there is no signal. Maybe you connected the polarity of the 2.2uF coupling capacitors backwards. Maybe you connected the pins of the transistors backwards. With the pins pointing down, looking at the flat face the pins are EBC left to right. European transistors are the opposite. Japanese transistors have the collector pin in the middle.

    When lighted, the red LEDs have a current of about 17mA which is fairly bright. The yellow LEDs get about 7.6mA which is not bright but is not dim.
    The blue LEDs get about 31.3mA which will probably burn them out.
     
  9. Rocky_circuits

    Thread Starter Member

    Nov 1, 2011
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    I thought that the resistors were rather backwards when looking at the schmematic. After testing, the blue LED's are definitely insanely bright compared to the others. Thank you for the calculation :)

    The thousandth time looking through I can't find a single fault. The only thing I'm not 100% on is the V+ on the V-ground. That just means 12v+ right? On IC1 I made an H shaped solder trail connecting pin 3, 5, 9, and 11. Then from one of those pins I just sent 1 wire to the V-ground on the Virtual ground circuit. There's no reason that wouldn't be wrong... hmm..

    Bah, I'll just try making it again. I just hope that the components in the circuit are correct. (minus the LED ones.) Or maybe I don't understand the circuit correctly. Anything that says +12V connects to the 12 volt power supply right?
    That V+ has me curious though, as potentially maybe that is the source of my problems.
     
  10. Audioguru

    New Member

    Dec 20, 2007
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    Yes, V+ is +12V. Then the two 100k resistors are a voltage divider feeding +6V to the input of the useless V-ground opamp that also has +6V output.

    There is your problem.
    Pins 3, 5, 10 and 12 connect together and to V-ground.
    Pin 11 connects to the power supply ground together with everything else that connects to the circuit ground.
    Pin 4 connects to the power supply +12V together with everything else that connects to +12V..
     
  11. Rocky_circuits

    Thread Starter Member

    Nov 1, 2011
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    I wish that was the problem, I just miscounted. It's soldered to the correct pins afterall. Ah well. Off to round two!
     
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