Color Organ Circuit

Thread Starter


Joined Sep 29, 2011
Hey guys,
I am currently making a color organ for a school project.
For those who don't know what a color organ is, it is essentially three sets of LED's that will light up depending on the frequency of the music that will be comming from an Mp3 player.
I have attached a .jpeg of the circuit I designed but the resistors might not be the right values and I am using TIP-142 darlinghton transistors.
I have tried running this circuit in multisim and it was not working so I am not sure what is the problem.
The circuit consists of three filters, HPF (high pass filter) LPF (low pass filter) and BPS (Band pass filter).
Would you guys have any suggestions or comments?



Joined Aug 21, 2008
I am not going to comment on your filters, I figure SPICE will tell you what you want to know about them. I see a problem with the interface between the LM324 amplifiers and the 2N2923's. The output of the LM324 cannot swing below 1 diode drop above ground. Also, there is no resistor to limit the base current to the 2N2923. To fix both shortcomings, I suggest putting the 1K resistor in series with the base of the 2N2923 and then putting an additional resistor (3.3k should work) from the base of the 2N2923. I suspect others will share other observations.


Joined Nov 16, 2007
Take a look at the following link. It has a working schematic. The opamp used is not the same but may be interchangeable with the LM324, you would have to compare the datasheets.

Color Organ


If your really determined to make your circuit work as well as understand it's workings then continue with it. You will learn more than just copying another circuit and building it.
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