This nifty sound level meter is a perfect one chip replacement for the
standard analog meters. It is completely solid state and will never wear
out. The whole circuit is based on the LM3915 audio level IC and uses
only a few external components. This circuit can also be integrated into
audio amp projects.
Circuit Schematic
| C1 | 1 | 2.2uF 25V Electrolytic Capacitor | |
| C2, C3 | 1 | 0.1uF Ceramic Disc Capacitor | |
| R1, R3 | 2 | 1K 1/4W Resistor | |
| R2 | 1 | 10K 1/4W Resistor | |
| R4 | 1 | 100K 1/4W Resistor | |
| R5 | 1 | 1M 1/4W Resistor | |
| D1 | 1 | 1N914 Silicon Diode | |
| Q1 | 1 | 2N3906 PNP Transistor | |
| LED1-LED10 | 10 | Standard LED or LED Array | |
| U1 | 1 | LM3915 Audio Level IC | |
| MISC | 1 | Board, Wire, Socket For U1 |
Notes
- V+ can be anywhere from 3V to 20V.
- The input is designed for standard audio line voltage (1V P-P) and has a maximum input voltage of 1.3V.
- Pin 9 can be disconnected from +V to make the circuit use a moving dot display instead of a bar graph display.
- Thanks to help from the forum, this circuit has been improved from the original version to include a peak detector for a more stable and viewable output. This page has been updated with the new circuit.
Post a Comment