VU LED Indicator Schematic

VU LED indicator is simpler and smaller than their analog, and very common in audio equipment. This version is based on National Semiconductor IC, and using the logarithmic version. Each LED operates with a 3dB difference from before, and the jumper is provided to allow dot or bar mode.

The circuit is completely conventional, and is based on application notes from National Semiconductor. The circuit is shown in the picture below and you can view it with a single IC and some discrete components. DC to the LED is almost filtered - C1 are included to ensure that the IC does not oscillate, and is not a filter cap.

This allows a higher LED current with lower dissipation than is the case if the DC is fully refined, and full smoothing would also require much larger capacitors. This will increase the size and cost of the project - especially important if you want to use in larger quantities that may occur with a mixer or analyzer.It could not be simpler. At the maximum level that you want to operate the equipment (as shown on the audio millivoltmeter or an oscilloscope with a signal applied), adjust VR1 so that the signal light to all the green LED (L1 is the most sensitive, and L10 showed the maximum level, so L1 to L8 should be lit ). If the input directly from the speaker output, an additional series resistor should be used in terminal "Aud" input to reduce the level. This can be determined by calculation (I leave it to you) or by experiment. As a guide, for 50W amplifier, an external resistance should be about 47k ohms.If you calibrate the meter for the power amplifier, set the output to a level below clipping. Adjust the level control until the LED turns on. In this way, if (L10) LED bulbs last when you're listening to music, you'll know that you are very close to clipping, and volume should be reduced.

Dancing Led Schematic

Dancing basic LED circuit LED lights up to ten in a row, to the music or speech is taken-up by a small microphone. Expanded version can drive up to ten strips, formed by up to five LEDs each, at 9V supply.

IC1A about 100 times amplify the audio signal take-up by a microphone and act as IC1B drive-voltage peak detector. its peak output in sync with the peak of the input signal and clock IC2, a ring decade counter capable of driving up to ten LEDs in sequence.An additional circuit allows the switch to ten strips, made by each of the five LEDs (max.), at 9V supply. It is formed by a 10mA constant current source (Q1 & Q2) common to all LED strips and the switching transistor (Q3), the movement of strips obtained from 2 to 5 series-connected LEDs. Therefore, a transistor and resistor Base are required to drive each strip is used.

Dancing LED circuit component list
R1: 10K 1/4W Resistor
R2, R3: 47K 1/4W Resistor
R4: 1K 1/4W Resistor
R5, R6, R7: 100K 1/4W Resistor
R8: 820R 1/4W Resistor
C1, C3: Ceramic or Polyester Capacitors 100nF/63V
C2: Electrolytic Capacitor 10μF/50V
C4: Capacitor Polyester 330nF/63V
C5: Electrolytic Capacitor 100μF/25V
D1: 1N4148D2-D11: LED (type and color)
IC1: LM358IC2: 4017
M1: electret microphone
SW1: Switch SPSTB1: 9V PP3 Battery

Additional series of sections:
R9, R10: 10K 1/4W Resistor
R11: 56R 1/4W ResistorEtc.
D12, D13: LED (type and color)
Q1, Q2: BC327Q3: BC337

Note: The sensitivity of the circuit can be varied to change the value of R4. C4 value can vary from 220 to 470nF in order to change the speed of the circuit-peak response to music. Adopt additional circuitry, just one item for R10, R11 Q1 and Q2 required to drive up to ten LED strip. Conversely, an item of R9 and Q3 is needed to encourage each of you decide to use the strip. Each R9 input pin must be connected to the output of IC2, in the D2-D11 LED display. R8 should also be eliminated. Whishing to use a lower number of LEDs or LED strips, pin # 15 of IC2 must be disconnected from ground and connected to the first output pin unused. For example: if you decide to use 5 LEDs, pin # 15 of IC2 must be connected to pin # 1, if you decide to use 8 LEDs, pin # 15 of IC2 must be connected to pin # 9, etc. are now drawing the circuit is about 10mA. Whishing using a wall-plug adapter instead of a 9V battery, you can provide a circuit at 12V, which allows use of up to 6 LEDs per strip, or at 15V, which allows use of up to 7 LEDs per strip.