thanks but I do not have that IC and I'd rather just use what I have available. I got two LM3916's which im thinking of adding later if the schematic with the lm324n works.Attached is a IC that has 7 audio filters and does much of the work. Just a thought.
https://www.sparkfun.com/products/10468I have no clue where that EQ IC in post #2 is sold, Digikey has never had it.
Ah alright I thought I need the 500 ohm resistors as a dropping resistor. Anyways the LM3916 part pf my schematic is exactly the same as the one show in the data sheet except I connected pin 3 with pin 9. I'll modify my resistors/capicitor values to use more cheaper parts, as for the rectifiers- i need to read up more on that as i'm current not sure of what their purpose is for this project. I'm a bit confused and what you mean by making an "active filter in the opamp bandpass filter circuit". Is my bandpass filter not an active filter already? Or do you mean to make an active lowpass filter and connecting that to an active highpass filter? Its a 0.51uF capicitor, on my design I added an extra 0 by accident and tried to cross it out.Your opamp probably will not work because it is not powered and is not biased.
You did not read the datasheet for the LM3916 to see that its LED outputs have regulated current so the 500 ohm resistor is not needed, 500 ohms is much too high anyway. But I cannot read your writing for the resistors in series from pin 7 to ground, their total value sets the LED current.
You have a huge expensive 0.68uF capacitor and a 1k resistor on the input when you could use a small less expensive 0.068uF (68nF) capacitor and a 10k resistor, or a very small 6.8nF capacitor and a 100k resistor. They cut frequencies gradually below 235Hz, no bass. Then the opamp feeds a 1k resistor that overloads it and a 0.039uf capacitor that cut frequencies gradually above 4100Hz, no highs.
The rectifier is passive and does nothing at low levels, the datasheet shows active rectifiers using an opamp so they rectify all levels.
Since you did not read the datasheet then the LM3916 might melt when many LEDs are turned on and are bright because the 12V supply voltage is much too high.
Your calculations show a passive gradual highpass and a passive gradual lowpass that together make a very poor bandpass filter. You should make an active filter in an opamp bandpass filter circuit.
Your calculations show a huge expensive 0.51uF capacitor and a 100k resistor but your schematic shows 0.051uF, which is it?
Ok I've remade my circuit how does it look like now? Also Is this the rectifier circuit you're talking about, its figure 22 in the data sheet. If so, since im thinking of only doing 3 filters for now( 20-250hz, 250-4000hz, 4000hz-20khz) would I be able to use the same rectifier for all three filters or would I need to change the R and C values? The data sheet also uses a different op amp than then ones I have would it still work with the lm324? And lastly, this rectifier circuit would replace my "peak detector" correct? Sorry for all the questions really trying to understand how all of this works.Audio is AC that alternates positive and negative over and over. But the LM3916 is active only for the positive parts of the input signal so the LEDs would be turned off for each half-wave of the input signal and at low frequencies they would flicker and at higher frequencies the LEDs would appear dimmed because they are turned on only half the total time.
The rectifier passes only the positive parts of the signal and its filter capacitor holds the peak voltage long enough for our vision to see its brightness and to avoid flickering on and off. But the diode needs about 0.65V for it to work which is near the signal level required to light the lowest LEDs of the LM3916 so they might not light with low levels. An active rectifier using an opamp is shown in the datasheet and it rectifies very low levels perfectly.
Your "filter" is a simple passive RC highpass filter amplified by an opamp and it feeds a simple passive RC lowpass filter. It is not an active bandpass filter. It is very simple so its slopes are gradual and not sharp. Its highpass and lowpass cross and reduce frequencies that both are reducing. An active bandpass filter has the RC parts inside its negative feedback loop and some active filters even use positive feedback to make sharp slopes or a narrow bandpass. active filters can use multiple RC networks and they have "orders":
With one RC it is a first order very gradual sloped first order filter.
With two RCs it is a second order filter that has sharper slopes.
With three RCs it is a third order filter etc.
An active highpass filter feeds an active lowpass filter to make a wide bandpass with sharp slopes. An active bandpass filter using one opamp makes a narrow bandpass.
Since these are not "brickwall" filters (vertical attenuation slopes, zero overlap), I recommend designing them so that there are gaps between the three passbands. This will increase the amount of time that all three outputs look different.im thinking of only doing 3 filters for now( 20-250hz, 250-4000hz, 4000hz-20khz)
ah ok so something more like 20-250, 300-4k, 5k-20k? And is figure 20 the recitifier you were talking about earlier? And how did the filters I made look?Since these are not "brickwall" filters (vertical attenuation slopes, zero overlap), I recommend designing them so that there are gaps between the three passbands. This will increase the amount of time that all three outputs look different.
ak
ok i did not know that amps couldnt drive 1k loads. Anyways I made some quick modifications the Capacitors are more than likely not standard values as I change them quickly since I did not have much time at the moment. Would I be able to use the half way peak detector show in the data sheet? I'd rather not have to buy parts. Also how do I properly biased my filters? The only biasing I have ever done involve diodes operating in specific regionsYou show second order active filters with opamps that are not powered, are not biased properly and the grounds are missing. Why do you use resistor values as low as 1k which need HUGE capacitor values?? Most opamps cannot drive a load as low as 1k.
The peak detector shown in the datasheet is fairly complicated and needs a positive and negative power supply. My peak detector uses an IC that has inputs and outputs that go all the way down to ground so a negative supply is not needed and the circuit is simple:
Ok so i found the schematic of this color organ. Would you recommend adding the part I circle which I believe its an audio amplifier circuit? Also I made a triangle around 2 resistors in series and a capacitor which seems to be what you're telling me to add. Did I do it correctly? Also just making sure, I'm going to need a second power supply since your peak detector circuit runs on 5V instead of 12V correct?The datasheet for the LM324 opamp and most other opamps shows that its voltage gain and output voltage swing are spec'd with a load of 2k ohms or more. There are a few opamps that can drive a load as low as 600 ohms.
Here is a short description of how the circuit should be designed:
The lowpass filter must be fed from a low impedance like the output of another opamp.
The input of the filters must be able to swing up and down but since you do not have an additional negative supply then the new added opamp's (+) input must be biased at half the supply voltage with 2 series resistors and a capacitor. Then its input and output can swing up and down with the signal. Since the lowpass filter opamp is DC-coupled on its input then it will also have its input and output swing up and down.
The highpass filter also must have its input and output swing up and down then the resistor to ground on its (+) input must be disconnected from ground and connected to the half-supply voltage resistors added for the lowpass filter. The resistor to ground on its (-) input must be disconnected from ground and connected to a capacitor to ground
The simple half-wave peak detector also must have its input swing up and down but must have an input that swings positive and negative. Then all the previous opamps need an added negative supply. Use my peak detector circuit instead since its input has a capacitor that blocks the DC from the highpass filter opamp.
Your half-wave peak detector has its transistor upside down but you should use my peak detector circuit instead.
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