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Build Your Own VU Meter: A 13-LED Circuit Design
Description
This circuit represents a straightforward design for measuring sound signal levels, tailored to meet diverse user needs. The system is adjustable, controlled by potentiometers TR1 (Level) and TR2 (Gain), subsequently rectified through diodes D1-D13. This rectification feeds into the main circuit comprised of diodes D3 through D13, along with transistors Q2 through Q13, and associated components. The visual indication of the level is obtained via the LED array, LD1-LD13, where each LED illuminates when the voltage reaches approximately 0.65V. The total current requirement for the complete system is 100mA. Additional LED units can be incorporated, with the current draw for each new LED accurately calculated.
Circuit diagram
Part list
- R1=47Kohm
- R2-3 =1Mohm
- R4-R7=1Kohm
- R5=100ohm
- R6=18Kohm
- R9-11-13-15-17=560ohm
- R19-21-23-25-27=560ohm
- R29-31=560ohm
- R8-10-12-14=4.7Kohm
- R16-18-20-22=4.7Kohm
- R24-26-28-30=4.7Kohm
- TR1=100Kohm Trimmer
- TR2=4.7Kohm Trimmer
- C1=10uF/25V
- C2=100nF/100V MKT
- C3=4.7uF/25V
- C4=4.7uF/25V
- C5=10uF/25V
- C6=47uF/25V
- C7-8=100nF/100V
- LD1-7=LED Green
- LD8-10=LED Yellow
- LD11-13=LED Red
- D1-13=1N4148
- Q1 ....Q13=BC550C - BC549B
- IC1=TL071
- IC2=7812 [With Heatsink]
All Resistors are 1/4W 1-5%
More about components
The circuit incorporates two integrated circuits: the TL071 operational amplifier and the 7812 voltage regulator. The TL071, a dual operational amplifier, is commonly utilized for amplifying and filtering signals. It provides high precision and low noise performance, crucial for accurate level measurement. The 7812 is a three-terminal positive voltage regulator, delivering a stable 7V output. It’s often coupled with a heatsink to dissipate heat generated during operation, ensuring reliable performance.