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Audio level indicator on the LM324

Chip LM324 is a precision operational amplifier and contains four independent channels. She works in a wide range of supply voltages from 3 to 30 volts. The output current of each channel does not exceed 10 mA. On the chip can construct a set number of interesting devices.  Scheme is relatively simple indicator of the audio signal, built on a chip LM324. Because the chip contains 4 outputs, the number of LEDs for the analyzer will also be four, one for each channel. The amplifier output is connected to the input indicator LEDs will light up depending on the frequency of play, at low input frequencies LEDs will flash column. The result is a very beautiful light and music effects. For best effect, you can use two chips, then it will be able to use 8 LEDs, we consider both options. Installation will not work if the input is connected to the line output from the computer sound card or headphone output does not work! During these experiments, it became clear that the chip can be adapted to the…

Equalizer LEDs Design

LED design is somewhat more complicated. Of course, by using a special control circuit can be simplified to the limit, but there lurked a little trouble. Most of these chips produces the output current up to 10 mA, and the brightness of the LEDs under the car may not be enough. In addition, the most common chip in yields on 5 LEDs, and it is only "minimum program". Therefore, for our conditions diagram on discrete elements is preferable, it can be extended without much effort.
The simplest LED display (Fig. 4) does not contain active elements and thus does not need power. Connection - to the unit under the scheme "mixed mono" or split capacitor, an amplifier - "mixed mono" or directly.
Fig. 4 The scheme is very simple and does not require the establishment. The only procedure - selection of R7. On the face value of the scheme to work with built-in amplifiers head unit. When working with power amplifier 40 ... 50 W resistance of this resistor should be 270 …

LM3916 Audio level meter

This project is intended to indicate the signal strength. This is done using a special LED driver LM3916 (analog signal level meter with display values ​​on the line LEDs). LEDs correspond to the standard values ​​of the scale signal from -20 dB to +3 dB, except 2dB.
Product Overview
Scheme is simple enough, it is almost the same as that contained in the documentation on the chip. In the circuit, the potentiometer is connected to terminals 6, 7, 8, and sets a value of 3 dB. It must be adjusted so that the signal at the input of 0dB 0dB indicator would simply burn. Before entering LM3916 worth transistor BC558. Its purpose is to strengthen the signal to logic 1 level chip. This is achieved by correcting the signal diode 1N4148, then filtering with a capacitor (as he does not pass the DC voltage in the case of hitting it on the input). In principle, this clamp level. 1M resistor is a bleeder resistor. Thus, its value and the value of the capacitor determines the retention level. This i…