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

Signal strength indicator on the 64 LEDs

I present to you a simple project indicator audio signal, a distinctive feature of this project from others is that in the scheme for each channel I primel 32 LEDs to get the long line. At the heart device - AVR microcontroller Atmel ATmega8535, ULN2803 - 8-channel key Darlington, moreover, operational amplifiers, his appointment think it's also clear. Sensitivity indicator is adjusted by resistors R32 and R33, for each channel separately. This project is my thesis work I did a couple of years ago, when the scheme came across sharilsya in folders on your PC, and decided to send to the site.

The scheme is quite large, reduce LED designation did not, the scheme can be found below:

As for the LEDs, it is convenient to replace the special LED bars, besides, they will look better.

The entire device is going on a breadboard, PCB did not draw who liked the project can draw the circuit board and send it to the forum. All radio components in the circuit can be replaced by a similar, resistor and capacitor can be placed close to par. The transistors may be replaced by any other similar. Crystal oscillator can be put on 14-16 MHz, is not critical. Photos of the device below:

When programming the microcontroller does not need to put fuse bits, ie we select the desired controller in the program, open firmware and click flash. If the device is assembled correctly, the circuit work immediately.

Original article sourse cxem.net

Audio power LED

General description:

This is a circuit with a two-color LED indicates how much power an amplifier delivers. The circuit is connected across the speaker terminals. At low power, the LED shows green light, at higher power, the color changes to orange to red. 

Circuit diagram:

Part list:

R1 = 10 k

R2 = 2.2 K?
R3, R4 = 100 Ω
C1 = 10 uF / 16 V
D1, D2 = 1N4148
D3 = duo LED red / green
T1 = BC547B

Audio Amplifier 250mW

General description:

This design can be used as a small booster. The amplifier is built around a balance staircase. 

The quiescent current is set by diodes D1 and D2. Due to the simplicity of the circuit is a closed-circuit current depending on the temperature of the diodes. When T2 and T3 a much higher temperature than the diodes, which can be annoying. The transistors cooling, then a solution. It is best to stick with some superglue., The two transistors on a small aluminum plate The supply voltage is 9 volts.

Circuit diagram:

Part list:

• R 1 = 4.7 K?
• R 2 = 82 K?
• R3 = 12 K?
• R4 = 1.8 kOhm
• P1 = 10 k
• C1 = 10 V μF/10
• C2 = 100 V μF/10
• C3 = 220 V μF/10
• D1, D2 = 1N4148
• T1 = 547 BC
• T2 = 337 BC
• T3 = 327 BC

LM 386 Amplifier circuit 1 W

 LM 386 general description:

This circuit is a signal line so that you reinforce a small speaker can drive with. The LM 386 is a number of versions available. The LM 386N-1 can deliver a power of 325 mW, the LM 386N-2500 mW, the LM 386N-3700 mW and LM 386N-4 can deliver one watt output. All versions can be used in the circuit. Using S1 is a bass boost (extra bass enhancement) to turn. The state is drawn from the bass-boost.

LM 386 circuit diagram:

LM 386 partlist:

R1 = 10 k
R 2 = 10 Ω
P1 = 10 k
C1 = 100 nF
C2 = 47 nF
C3 = 470 uF
C4 = 10 uF
C5 = 33 nF
IC1 = LM 386
S1 = switch

BC549C and BC547B Microphone amplifier

BC549C and BC547B microphone general description:

The preamplifier amplifies the output signal of a microphone, so that it can be. The further amplified by a power amplifier The circuit supplies the output to a signal line. With two transistors, it is not difficult to build such a circuit. The amplifier produces little noise. In the shown embodiment, the circuit is suitable for microphones 500 and 600 Ω. 200 Ω R1 microphones should be reduces to 220 Ω and C1 should be increased to 4.7 uF. The gain is set by R2. If the average declared value of 22 K? Can be used. The maximum gain is about 200 times.

BC549C and BC547B microphone circuit:

BC549C and BC547B microphone part list:

R1 = 470 Ω
R 2 = 22 K?
R3 = 12 K?
R4 = 47 k
R5 = 820 Ω
R6 = 100 Ω
R7 = 1 k
R8 = 100 k
C1, C4 = 2.2 V μF/16
C2 = 47 V μF/16
C3 = 470 nF
T1 = BC 549C
T2 = BC 547B

ISD2560 Speech Recorder

ISD2560 circuit diagram:

ISD2560 part list:

R1 = 1k
R2 = 470k
R3 = 10k
R4 = 5k1
R5 = 4k7
R6,7 = 100k
R8,9 = 1M
R10 = 10R
C1-10 = 100nF/63V
C11 = 47nF/63V
E1,4 = 220uF/16V
E2 = 4u7F/16V
E3 = 22uF/16V
IC1 = ISD2560 + socket
IC2 =LM78L05
IC3 = LM386 + socket
MIC = Condensator microphone
S1,2 = Pushbutton (S1 = Start and Pause. S2 = Stop and Reset)
S3 = Change-over switch
Hψjttaler = 8R speaker