# Simple LED music light circuit

In this post, I am going to show you a simple LED music light circuit.

It is interesting because of similar to a VU meter circuit.
Music can change the LED light level gamut.

We may apply this circuit display music dancing.

Even more importantly it may a nice teacher. To learn an op-amp comparator voltage.

### Operation of this circuit

You know well that I try to make a simple circuit and can use in everyday life. To save and great learning.

Also, this circuit is easy. Look at the circuit below.

In this circuit uses OP-AMPs – LM318—Single High-Speed Operational Amplifier, IC1 to IC5. We set them into a voltage comparator form circuit.

Here is the step of the operation:

Set one pin is a voltage reference pin (pin 2). Get the voltage from the supply. And use a voltage divider between R1 and R7. The voltage drop across R7 is the voltage reference, 2V.

We use this voltage to compare the input voltage.

The input has R2, R3, R4, R5 and R6 resistor in series. It causes the voltage across each resistor is the same.

Suppose that…

The input voltage is 5Vp-p. So, the voltage across R2 = R3 = R4 = R5 = R6 = 1V. And, the voltage reference, we have 2V.

This circuit will compare the voltage at IC4. And, measure the voltage at the input pin of IC4 is 2V. Which it equals voltage on the positive pin of IC4.

So its output does not have the current to drive the LED light up.

We need more input voltage into this. To make IC4 runs.

The next LED will light up arranged in the order of the input voltage.

#### Parts you will need

IC1-IC5: LM318 Fast General-Purpose Operational Amplifiers
0.25W Resistors, 5% tolerance
R1: 10K
R2-R6: 1K
R8-R12: 100 ohms
LED1-LED5: LED as you want

Not only that…

With this principle, you can get LED level circuit.

This is 1.5V battery tester circuit diagram.

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