LED VU Meter Circuit

 

Introduction:

                Presented here is a project detailing the construction of an LED VU Meter Circuit utilizing the LM3914 IC. This circuit serves to display audio levels in various audio equipment such as stereo amplifiers, CD players, and DVD players. The project is characterized by its simplicity and moderate complexity, with an estimated cost of approximately Rs.150.

Connection:

               The circuit diagram is straightforward to create. Begin by placing and soldering all components onto a DOT board. Connect the negative (-) terminal of the 1st LED to the 10th pin of the IC, followed by similarly connecting the 2nd to the 11th pin, the 3rd to the 12th pin, and so forth up to the 10th LED connected to the 1st pin of the IC. Once the negative terminals are connected, join the positive (+) terminals of all LEDs together. Connect this common positive to the 3rd pin of the IC, serving as the voltage input, linked to the positive side of the power supply connector. Ground the circuit by connecting the 2nd and 4th pins of the IC to the negative side of the power supply connector. The 9th pin of the IC functions as the mode pin; when not connected to the positive side of the power supply, the LED mode is in Bar Mode, whereas when connected, it operates in Dot Mode. Lastly, the 5th pin of the IC serves as the input section, crucial to the functionality of the project.

Circuit Diagram:

Note:

         Ensure that one speaker line from the amplifier is connected to the audio input of this circuit.

Working:              

                This circuit operates in direct proportion to the music sound level. Connect the speaker wire from the amplifier to the audio input of the circuit. The circuit takes an analog input from the audio amplifier source and drives ten LEDs with audio signals. Two display modes, Dot Mode and Bar Mode, can be selected using a two-way switch. In Dot Mode, a single LED moves from top to bottom, representing the audio graph, while in Bar Mode, all LEDs activate and move sequentially.

                The LM3914 IC is the core of the circuit, functioning as a voltage level sensor that switches ten LEDs on and off based on the increase and decrease of DC voltage at its 5th pin. The operational voltage for this schematic circuit ranges from 5 volts to 12 volts DC.

Part List:

1)     LM 3914 IC =1

2)     18 Pin IC Base =1

3)     5mm LED =10 (any colour)

4)     Switch =1

5)     10KΩ ¼ W Resistor =1

6)     2.7KΩ ¼ W Resistor =1

7)     3.9KΩ ¼ W Resistor =1

8)     1μF Capacitor =2

9)     1N4148 Diode =2

10)     DOT/ZERO Board =1

11)     Some Wires

Uses of this Circuit:

                                This circuit measures the level of audio coming through the speaker, making it a valuable tool for audio monitoring applications.

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        By,

G. Guruvel Sarveshwar,

EEE Dept.