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I found this(link below) video on Youtube, it's a RGB stereo Vu meter based around (obsolete) LM3915 dot/bar display driver. Since author didn't provide schematics and I want to build something similar, I'm curious how to do it. But, I'm curious more about what dot/bar display driver does in whole story?

My idea is to use Y 3.5mm adapter from PC, then somehow split signal into low, mid and high tones, amplified them and what now? Can someone explain what dot/bar display driver does?

Video: https://www.youtube.com/watch?v=dIYQ0l-WAZI

Thanks!

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  • \$\begingroup\$ The LM3915 is a VU meter display driver. It is the very heart of the gadget in the video. \$\endgroup\$
    – JRE
    Commented Jul 3, 2020 at 21:45
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    \$\begingroup\$ Read the datasheet. It will answer most of your questions about the 3915. The 3915 is a single channel VU meter IC. It doesn't change colors. It can do a bar graph or a moving dot. Anything else you saw in the video was done with additional circuitry. \$\endgroup\$
    – JRE
    Commented Jul 3, 2020 at 22:13

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The chip is nothing more than a chip that takes in audio, and compares the audio amplitude with 10 internally generated reference voltages, and these reference voltages are logarithmically spaced to provide a decibel output. Each of the comparator turns on a LED if the audio signal exceeds the reference voltage.

In reality the chip has quite a lot of features, such as dot mode or bar graph mode can be selected.

The LEDs are just set on or off based on voltage, so the color is up to the chosen LED that is being lit.

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  • \$\begingroup\$ So it is multi channel comparator? How LEDs change colors, and why logic skips some LEDs(eg. turns on LED at the top, but LED below is off). \$\endgroup\$
    – Pararera
    Commented Jul 3, 2020 at 21:52

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