Building the meter
We’ve engineered our meter on a standard 830-tiepoint breadboard, but the final version would receive a purpose-built circuitboard or general-purpose veroboard. The audio input can come from your phone or tablet via a 3.5mm to 3.5mm stereo cable. We’re using 5mm high-brightness white LEDs but you can choose any colour you wish. A Fritzing overlay diagram gives you a closer view of how we engineered the project.