This is Circuit LM3914 LED VU Meter. use IC LM3914 and Transistor BC109C. For Display power Music by LED
This be LED VU Meter by IC LM3914 circuit show with LED convenient for the stereo or sound all signal. This easy circuit again because use IC LM3914 show get 10 the level. Build easy because use the integrated circuit just one and the price is inexpensive. The detail is all , see in the circuit better.
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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. 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
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The circuit, is a comparator, can measure with step of 1Volt, the voltage of battery of car. The clue of voltage become after comparison of voltage of battery, that is applied in the inverting inputs of amplifiers, with voltages of reference that are produced by a Zener D1, the value of which is such so that it present good thermic stability. With the RV1, we regulate the gradation of voltage that we want. The optical clue become from four Led.
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This circuit uses just one IC and a very few number of external components. It displays the audio level in terms of 10 LEDs. The input voltage can vary from 12V to 20V, but suggested voltage is 12V. The LM3915 is a monolithic integrated circuit that senses analog voltage levels and drives ten LEDs providing a logarithmic 3 dB/step analog display
LED current drive is regulated and programmable, eliminating the need for current limiting resistors. The IC contains an adjustable voltage reference and an accurate ten-step voltage divider. The high-impedance input buffer accepts signals down to ground and up to within 1.5V of the positive supply. Further, it needs no protection against inputs of ?35V. The input buffer drives 10 individual comparators referenced to the precision divider. Accuracy is typically better than 1 dB.
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This circuit is quite useful for displaying the states of digital lines. The two 330R resistors may need to be changed as the circuit I generally use is using a tri-colour LED(3 legs) with common cathode. Other LED’s may need more or less current.
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