This simple car battery monitor allows us to know the voltage of the battery at all times. To achieve this, 4 LEDs are placed somewhere on the dash of the car. Each LED has a label indicating the battery voltage at that time.
8 LED VU meter circuit using LM324 IC
This circuit can be used to display the variation of an audio signal in a group of 8 LEDs, behaving like a VU meter. We could use any specific integrated circuit used for VU meters, but we decided to use a readily available LM324 op amp. I.C.