AUDIO LEVEL METER ELECTRONIC DIAGRAM

AUDIO LEVEL METER ELECTRONIC DIAGRAM

It consists of only few components. IC LM3915 converts the audio analog voltage and display it to the LED. Here is the schematic :

Parts list :

•     Resistor R1 : 1k2
•     Resistor variable R2 : 10k
•     IC : LM3915
•     LED indicator LED1-LED10 : LED 5mm
•     12V power supply

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TV Relative Signal Strength Meter

This circuit was designed to assist the installation of TV antennas. The signal is monitored using a small portable TV set and this circuit monitors the output of the TVs FM detector IC via a shielded lead. To initially calibrate the meter, adjust trimpot VR2 to zero the meter. Trimpot VR1 is a sensitivity control and can be set for a preset reading (ie, 0dB) or can be calibrated in millivolts. Rotating the antenna for a minimum reading on the meter (indicating FM quieting) gives the optimum orientation for the antenna.

Circuit diagram:

TV Relative Signal Strength Meter Circuit Diagram

Author: Ted Sherman Copyright: Silicon Chip Electronics

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LM339 Using for LED VU Meter

This circuit in below uses two quad voltage comparator using IC LM339 to illuminate a series of 8 LEDs indicating volume level. Each of the 8 comparators is biased at increasing voltages set by the voltage divider so that the lower right LED comes on first when the input is about 400 mili volts or about 22 mili watt peaks in an 8 ohm system.


The divider voltages are set so that each LED represents about twice the power level as the one before so the scale extends from 22 mili watts to about 2.5 watts when all LEDs are lit. The sensitivity can be decreased with the input control to read higher levels. I have not built or tested this circuit, so please let me know if you have problems getting it working. This is the power levels should be as follows:
· 1 LED = 22mW
· 2 LEDs = 42mW
· 3 LEDs = 90mW
· 4 LEDs = 175mW
· 5 LEDs = 320mW
· 6 LEDs = 650mW
· 7 LEDs = 1.2 Watts
· 8 LEDs = 2.5 watts

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