The operation is as follows:
1. Power on Arduino UNO board using a USB A-B cable. As soon as you power on the LCD, it displays VU meter on the first row and bars on the second row of the LCD.
2. 10k potmeter VR1 can be used to adjust the contrast of the LCD.
3. If we connect the input from a music player to analogue input pins A2 and A4 of Arduino board through two wires, we can easily see the changes in the bars and letters L and R on both rows of the LCD, simultaneously, as shown in Fig. 2.
The article was originally published on January 27, 2016. It has been updated recently.
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