DIY LED Equalizers

Select an equalizer integrated circuit. There are now many integrated circuits (ICs) available that handle most of the sound processing functions essential to this project. For example, some ICs take an incoming audio signal and splits it into seven frequency channels. They then measure the amplitude value of each channel and output an integer value. This value is used by the micro-controller to illuminate the LEDs.

Select LED lights. There are two ways you can go: discrete LEDs or LED bargraph displays. LED bargraph displays are small banks of lights with any where between five and 20 segments. One LED bargraph display should be allocated to each frequency channel. With your micro-controller, you can program the display to illuminate according to the amplitude value of a given frequency channel. If you are using discrete LEDs, you can determine which individual bulbs will light at given amplitude values.

Program the micro-controller. There are popular micro-controllers for hobbyists that are open source, so other than the cost of the device itself, the development environment is free.

Gather components. The great thing about equalizer ICs is that they handle so many processing functions on the chip, such as switched capacitor filters, and oscillator and a output multiplexter. This functionality reduces the required external components to one capacitor and one resistor.

Assemble the circuit on a breadboard. Test the circuit first before soldering.

Design a printed circuit board (PCB). After you have draw the diagram, transfer it to a blank PCB. Etch the circuit diagram onto the board and drill holes where the component leads will go.

Solder components onto PCB. Use proper soldering techniques to ensure that you do not overheat your components.