Schematic Rise

Friday, November 7, 2014

Simple Stereo VU Meter

I like to see lights move to music. This project will indicate the volume level of the audio going to your speakers by lighting up LEDS. The LEDS can be any color so mix them up and really make it look good. The input of the circuit is connected to the speaker output of your audio amplifier. You want to build two identical units to indicate both right and left channels. The input signal level is adjusted by the 10k ohm VR. If you wish to make a very large scale model of this unit and hang it on your wall there is an optional output transistor that can drive many LEDS at once. The unit I built drove three LEDS for each output. The sequence of the LEDS lighting are as follows Pin 1, 18, 17, 16, 15, 14, 13, 12, 11, 10.

8 Stage LED VU Meter

The circuit below uses two quad voltage comparators (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 millivolts or about 22 milliwatts peak in an 8 ohm system.

8 Stage LED VU Meter Circuit diagram :

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 milliwatts 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. 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

VU meter

This circuit can control analog moving coil meters, for use as a VU meter. The circuit is left connected to the line terminals of the amplifier. VU meter works pretty simple. T1 and T2 increase the signal strength. The signal is then rectified by the two diodes and applied to the meter. The capacitors C3 and C4 ensure that the voltage is slightly flattened and the meter responds less quickly. After building the circuit, it must be calibrated. For this purpose, the VU meter connected to a tone generator which delivers 0.3V at 1000 Hz. Then P1 is fully open, that is to say that the wiper of P1 is located at the entrance. Then P2 is so cut that regulates the meter full deflection. P1 is then adjusted so that meter reads 0.5 mA (= half the maximum).

For a stereo VU meter circuit to be built twice.

R1 = 1 M
R2 = 820 Ω
R3 = 2,2 kohm
P1, P2 = 100 k
C1 = 330 nF
C2 = 22 uF
C3 = 1 uF
C4 = 470 uF
T1, T2 = BC 547B
M1 = 1 mA meter

Schematic Rise

Friday, November 7, 2014

Simple Stereo VU Meter

Thursday, November 6, 2014

8 Stage LED VU Meter

Tuesday, August 26, 2014

VU meter