lm3916 help

Thread Starter

fkuk

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



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:

Audioguru

Joined Dec 20, 2007
11,251
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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