This DIY project illustrates a simple and effective method of converting an audio signal into a visual LED display using the LM3914 LED driver IC. The circuit responds to the amplitude of an audio or music signal and displays it as a rising LED pattern, making it useful as an audio level indicator or music visualiser.
A 230V AC mains supply is stepped down, rectified, and regulated to provide a stable 5V DC supply. The audio input is taken through an audio jack and suitably conditioned before being applied to the input of the LM3914. The IC internally divides the input voltage into ten levels and drives the LEDs sequentially as the audio level increases. Higher sound intensity causes more LEDs to glow, forming a clear bar-type display.