Hello everyone! First post here so bare with me if i go the thread wrong.

It's been a month since i started a color organ project based on great scott's video on youtube which uses an arduino. I ordered all the parts from ebay and when i built the circuit on a breadboard i figured out that the msgeq7 ic , which was used to seperate the audio into bands , was a fake! My time schedule does not allow me to order another one so i thought i would use simple passive R-C filters. I built a 2nd order high pass(1st order wasnt "accurate" enough) and a 1st order low pass. Now, the analog input on the arduino reads values of about 1~8 for the high frequencies and 2~80 for the low freq. My question is... what's a good alternative to filter the audio without having so much attenuation given that i only have npn and a couple pnp transistor, no inductors and a tl082 opamp which i cant really use because i dont know how to get negative Voltage for the power rails.

Any help would be appreciated, Thanks in advance

 

Welcome to AAC!

It would be helpful if you posted a schematic of your circuit, describe what you mean by "not accurate enough", the frequency range and amplitude of the input, and what output you desire.

 

Hello again, and thanks for the quick response.

By not accurate enough i mean the filter had a small roll-off and the output was not what i wanted when testing it by ear... Therefore i made a 2nd order high pass. However that made the output signal even weaker. The input is any audio source with a jack (, so i guess the amplitude is a few mV. The output i want is something that can be read by the analog input of the arduino. It doesn't have to be exactly in the 0-1024 range.. but 1~4 on the high frequencies is a bit too low. Again, what i want is a larger reading from the filters on the analog inputs.. Hope i explained better

Here is the schematic:

 

Relevant portion of schematic for convenience:

what i want is a larger reading from the filters on the analog inputs

Each filter stage costs you half of the amplitude, and you're giving up amplitude with R1/R2.

If you use an active filter, you can have gain if you desire.

 

I am not able to make an active filter at the moment... What i tried was to amplify the signal from the passive filters with a tl082 but that didnt work.. Arduino got crazy readings. Would i be able to make active filters with lm386's or the tl082? Cause , that's all i have at the moment.

 

What i tried was to amplify the signal from the passive filters with a tl082 but that didnt work.. Arduino got crazy readings. Would i be able to make active filters with lm386's or the tl082?

TL082 should work, it would be a waste of LM386.

There's an active filter design app at http://www.analog.com/designtools/en/filterwizard/

 

Eventually i got it to work. The only problem i have now is i wanna use a 12v Power supply to power both the arduino(through the vin pin) and the op amp , but for the tl082 i use a virtual ground.. Can i do that or should i use different supplies?