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 two modes of operation, the first of which is already listed above - flashing LEDs individually, besides flashing corresponds to the input frequency range, the stronger low frequency, the higher the LED lights pole.

The second mode - joint flashing. In this mode, all the LEDs light up together. In this case, the output of the power amplifier and connect the negative input of the indicator.

In the first scheme, the construction of the variant of the indicator on a single chip. The effect is not very entertaining, but I advise you to start to collect that way, and then if everything is working properly, and you can connect a second chip.

In the video clip demonstrated the operation of a single chip, the LEDs are working together, then there is a circuit connected to the second embodiment.

Indicator is able to work together with any power amplifier, regardless of the supply voltage of the amplifier power, only do not raise the maximum allowable stress indicator, which is 30 volts.

In those cases where you need to combine the light with an amplifier that runs on dual supply, you need to use a voltage of 12 to 24 volts.LEDs fit literally any colors to your taste, you can apply one color LEDs, you decide.

Variant of the indicator on two chips:

To display operated in the "column", you need to connect the output of the amplifier plus the power supply indicator and an input razhim this can only be used when the power amplifier and the indicator powered from a variety of sources, otherwise there is a danger of burn VLF output stage!

Original article sourse cxem.net

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 ... 470 ohms.Diodes VD1 ... VD7 - any silicon with forward voltage drop of 0.7 ... 1 and permissible current of at least 300 mA.

Any LEDs, but the same type and color glow with operating current 10 ... 15 mA. Since LEDs are "fed" by the amplifier output stage, their number and increase the operating current in this circuit is impossible. So we have to choose the "bright" LED indicator or find a place where it will be protected from direct light. Another disadvantage of the simplest design - small dynamic range.

To improve the work required indicator to the control circuit. In addition to greater freedom in the choice of the LEDs can be simple means to generate any type of scale - from linear to logarithmic, or "stretch" the only one site. Indicator diagram with a logarithmic scale is shown in Fig.5. The dotted line shows the optional items.

Fig. 5

LEDs in this scheme the control keys on the transistors VT1 ... VT5. Thresholds options specify diodes VD3 ... VD9. Picking up their number, you can change the dynamic range and scale type. Overall sensitivity of the indicator is determined at the input resistors. The figure shows the approximate thresholds for the two variants of the scheme - with single and "twin" diodes. The basic version of the measuring range - up to 30 watts into 4 ohms, with single diodes - up to 18 watts.

HL1 LED lights continuously, it means the beginning of the scale, HL6 - overload indicator. Delay capacitor C4 0.3 ... 0.5 seconds extinction LED that allows even notice briefly overloaded. Storage capacitor C3 determines the return stroke. It is, by the way, depends on the number of LEDs glowing - "column" of the maximum begins to subside quickly, and then "brakes". Capacitors C1, C2 at the input only when working with integrated amplifier recorder. When dealing with a "normal" amplifier exclude them. Number of input signals can be increased by adding a chain of resistors and a diode. The number of cells can be increased simply indicating "cloning", a major limitation - the "threshold" diodes should be no more than 10 and between the bases of adjacent transistors must be at least one diode.

LEDs can be any, depending on requirements - from single LED to LED assemblies and panels, high-brightness. Therefore, the diagram shows the current-limiting resistors ratings for different operating currents. The remaining details of any special requirements are not established, transistors can be used almost any structure with npn collector power dissipation of 150 mW at least twice and reserve current collector. Transfer coefficient of the base current of these transistors must be at least 50, but better - more than 100.

This scheme can be simplified somewhat, with the side effect of new properties appear, very useful for our purposes (Fig. 6).

Fig. 6

Unlike previous schemes, where transistor cell were connected in parallel, series connection is used here "column". Threshold elements are transistors and open themselves, they in turn - "bottom up." But in this case depends on the threshold voltage. The figure shows the approximate indicator thresholds at a supply voltage 11 V (the left edge of the rectangle) and 15 (right border). It is seen that with increasing voltage is shifted most border indicating the maximum power. In the case of the amplifier, the power of which depends on the voltage of the battery (and there are many), this "auto-calibration" can benefit.

However, the fee is - increased load transistors. Through the lower scheme transistor current flows all the LEDs, so the use of indicators with a current 10 mA transistors also require appropriate power. "Cloning" cell further increases the scale unevenness. Therefore, 6-7 cells - is the limit. Assignment of the remaining elements and their requirements - are the same as in the previous scheme.

Slightly modernized this scheme, we obtain other properties (Fig. 7). In this scheme, unlike previously discussed, there is a glowing "ruler". At any time, only one LED lights, simulating the movement of arrows on a scale. Therefore, the power consumption is minimal and in this scheme can be applied low-power transistors. The rest of the scheme does not differ from those discussed previously.

Threshold diodes VD1 ... VD6 designed to safely disconnect idle LEDs, so if there will be a weak illumination superfluous segments, you must use diodes with a large forward voltage connected in series or two diodes. "Cloning" cells reduces the brightness of the upper segments of the scheme, to address this instead of resistor R9 need to enter the current generator. And we agreed - not to complicate.Therefore, in this case, an 8-cell - is the maximum.

Original article sourse cxem.net

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 is done for fast signaling and its slow decline. The timing and the recession can be adjusted by changing the values ​​of resistor 1M to another.Easy installation of the diode is not used as a direct drop 0,6 V diode cause an error, but the transistor compensates for this fall.

LM3916 Audio level meter

LM3916 can light one LED, respectively. input value, and the LEDs of the column to the bottom of the current value. These modes are switched connection to supply + 9 conclusion (column) or leaving it open (one LED). In column mode, the energy consumption indicator of high enough and it can lead to high currents passing through the GND terminal of the chip. To avoid problems that may arise, use 0.1μF decoupling capacitor in nutrition chip. All conductors desirable to GND as short as possible and finish at the same point. LM3916 can be replacement for LM3915, but the range of measurement would be very limited and will not meet the standard scale signal values.

Technical realization

The scheme has been assembled on the breadboard. Between the LEDs and earth, the tantalum capacitor has been set to filter out interference and leakage that may occur. Indication implemented on the final scale of LEDs but you can use just the LEDs. At the entrance stands the plug from the headphones, LED mode is selected by jumper.

Original article sourse cxem.net