Color LED Organ

Color LED Organ

Abstract

This project utilizes a series of capacitors and transistors to achieve a visual representation of any audio source that can be output to a 1/8” audio jack.  This system utilizes a 12VDC/600mA power source and amplifies, filters, and rectifies the audio signal to drive the LED light system.  The LED system is established using a series of transistors rather than standard IC amplifiers.  Difficulties with the project included getting the layout on one side, which increased the size of the PCB overall, and switching the positive and ground leads of the 12V input, which caused the 12V input to have to be soldered on the back side of the PCB.

Description

Figure 1

Fig 1. LED Organ Triple Deluxe II PCB with Components.

This circuit allows one to “see” their music, using a series of LEDs and a circuit to display the LEDs in a manner that goes along with the different frequencies of music.  It is a simple display of the different ways digital music is output to audio devices, and utilizes the same functions a speaker would use only displaying the light form as opposed to audio.

Figure 2

Fig 2. Circuit and layout, LEDs now shown.

Not counting the LEDs, the entire circuit is established only using transistors, resistors, and capacitors (as well as the audio and voltage inputs).  This increases simplicity of the system tremendously while reducing the control of the system somewhat.  The goal of the circuit is to take an audio signal, and attenuate and amplify it to achieve enough voltage to switch the transistors on or off that govern the LEDs.  The LED colors correspond to the different frequencies of the sound ordered from high to low blue, green, red.  Each of these frequencies is obtained by constructing a system of filters using the capacitors that offer desired pass bands corresponding to each frequency color, as seen in fig 2 below.

Figure 3

Fig 3. Frequency responses of the different LEDs, ordered from left to right - red, green, blue.

The system was done using a layout completely done on one side for additional challenge.  Most of the challenge in the circuit is involved in the soldering, due to the lack of ICs present on the board.  A board without ICs generally require very little debugging, and this circuit is an example of that.  It is important to note that the Power input is on the opposite side of the PCB, which was due to a mistake in the layout.  It was assumed incorrectly which pin was the voltage pin and which was the ground pin on the voltage input, which means the input had to be reversed for the system to function correctly.  This was resolved by simply mounting the voltage input on the back of the PCB, which allowed the system to function correctly without having to redo the entire PCB layout.

Color LED Organ

Fig 4. System LEDs. The order of the LED rows from left to right - blue, green, red, red, green, blue.

The voltage input utilized was 12VDC with a 600mA maximum.  This is a relatively high power for a circuit of this size and caliber, but it was used to achieve desired brightness of the LEDs.  The 10k potentiometer (VR1) seen in figure 1 can be adjusted to lower or increase brightness to desired levels as well.  It is important to keep in mind that many of the circuit values can be adjusted to achieve desired brightness and filtering results, which may or may not increase overall complexity of the circuit. 

Conclusion

This project was very satisfying overall, aside from the complications presented during the layout mixing up the voltage and ground pins, it was very simple to construct and understand.  I would recommend this project to anyone wanting a moderate challenge who wants something they can easily see the results of and can get some entertainment value out of as well.

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