lm3916 help

Discussion in 'The Projects Forum' started by fkuk, Dec 17, 2009.

  1. fkuk

    Thread Starter New Member

    Dec 17, 2009
    7
    0
    here is my circuit so far

    [​IMG]

    IN THE PICTURE IVE GOT IT WRONG IT IS NOT LM351 ITS MENT TO BE LF351

    i need the 20mV of the microphone to be 1.25v for the lm3916 using the lf351

    so far if i connect pin 5 from the lm3916 to the microphone + pin all the lights light up but if i change the 1K ohm resistor to 20k ohm only 3 lights are on constantly and the other lights light up as you make noise but the noise has to be very close to the microphone and loud

    can someone help me?
     
    Last edited: Dec 17, 2009
  2. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    go here and check out my Hard Drive activity meter I built around the LM3916 VU meter IC >>> http://www.morse-code.com/id201.htm

    My site is under "re-organization" right now, but I have this circuit already up there along with some others....
     
  3. fkuk

    Thread Starter New Member

    Dec 17, 2009
    7
    0
    that has nothing to do with a microphone
     
  4. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234

    well, you will have to just change the input to a Mic pre amp circuit then.... . Here is a MIC pre amp circuit that will work with it here on the bottom of this page http://www.morse-code.com/id194.htm .... just replace the op-amp circuits and connect the output of the mic pre amp circuit to the 10K variable resistor (R10) input of the VU meter IC....
     
  5. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The input of an LM3914, LM3915 or LM3916 needs at most a 1M resistor to ground at its input pin5 to stop all the LEDs from lighting. The audio from the preamp can be capacitor-coupled to it.
    The output from the electret mic is too low to light even the first LED (unless you scream close to it). The input must be 89mV to light the first LED.
    So connect the opamp as a preamp.
    The electret mic is normally powered from a 10k resistor not a 1k resistor.
    The 5V regulator does not have the recommended capacitors and is not needed anyway. A resistor can replace it to share the heat with the LM3916 since your supply voltage of 12V is too high (only 3V to 6V is needed if the LEDs are 1.8V red ones).
     
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