Mains Voltage Indicator with a LED.

This is a mains 230V AC voltage indicator and is a LIVE CIRCUIT, so take care.
The Resistor has to be a fusible ceramic wire wound and the capacitor 630V AC or higher capacity.
This circuit has been drawn from my memory and i have not tried it out again, just see if it is ok and then try.
You should use the fuse of 100mA a slow blow if you want but it is very important.
This circuit has to be enclosed in a plastic sealed enclosure to avoid contact.

Read more Source:http://schematics.blogspot.com/2004/11/mains-voltage-indicator-with-led.html
Thank you.

High-Performance 56W Audio Power Amplifier with Mute LM3876 -

The LM3876 is a high-performance audio power amplifier capable of delivering 56W of continuous average power to an 8 load with 0.1% THD+N from 20Hz-20kHz.The performance of the LM3876, utilizing its Self Peak Instantaneous Temperature protection circuitry, puts it in a class above discrete and hybrid amplifiers by providing an inherently, dynamically protected Safe Operating Area. SPiKer protection means that these parts are completely safeguarded at the output against overvoltage, undervoltage, overloads, including shorts to the supplies, thermal runaway, and instantaneous temperature peaks.The LM3876 maintains an excellent signal-to-noise ratio of greater than 95dB (min) with a typical low noise floor of 2.0µV. It exhibits extremely low THD+N values of 0.06% at the rated output into the rated load over the audio spectrum, and provides excellent linearity with an typical rating of 0.004%.

Features

• 56W continuous average output power into 8Ω

• 100W instantaneous peak output power capability

• Signal-to-Noise Ratio >= 95 dB(min)

• An input mute function

• Output protection from a short to ground or to the supplies via internal current limiting circuitry

• Output over-voltage protection against transients from inductive loads

• Supply under-voltage protection, not allowing internal biasing to occur when V_EE + V_CC <= 12V, thus eliminating turn-on and turn-off transients

• 11-lead TO-220 package

• Wide supply range 20V - 94V

Part list

Resistor:
R1, R3 = 1 k
R2, R4, R5 = 18k
R6 = see text
R7 = 10R, 5 Watt
R8, R9 = 22k

Capacitors:
C1 = 2.2 uF
C2 = 220 uF, 160 V
C3 = 22 uF, 40 V
C4 = 47 pF
C5 = 100 uF, 40 V
C6 = see text
C7, C8 = 100 nF
C9, C10 = 1000 uF, 40 VInductors:
L1 = 0.7 uH – see text

Integrated circuits:
IC1 = LM3876T

Miscellaneous:Heat sink for IC1

Air-cored inductor L1 consists of 13 turns of 1mm dia. enamelled copper wire with an inner diameter of 10mm. The completed inductor is pushed over R7 and its terminals soldered to those of the resistor.All electrolytic capacitors must be mounted upright. The amplifier can be muted with a single-pole switch connected to the MUTE input (pin8). This function is enabled when the switch is open. If muting is not required, solder a wire bridge across the mute terminals on the board. Boucherot network R6-C6 is not normally required in this application, but provision has been made for it for use in other applications. According to the manufacturers, both chips are optimalized for a load of 8 Ohm. The output power is lower when a 4 Ohm load is used or when the supply voltage is reduced. When a 4 Ohm load is used, the SPIKE protection becomes active when the supply voltage is about 27V, resulting a in a reduction of the power output to 10W. This means that it is not advisable to use loudspeaker with an impedance

50W from a 12 V battery- TDA1562Q . . .

The integrated output amplifier described in this article consists of little more than one integrated circuit. It is intended especially for use in motor vehicles and other batteryoperated applications. Although it appears simple and hardly worth looking at, the amplifier can produce an appreciable audio power output.

technical dataPropertiesHigh power output through Class-H operation
Low power dissipation during reproduction of music signals
Proof against short-circuits
Protection against excessive temperatures
Standby switch
No power-on or power-off clicks
Visible error indication
Measurement results (at Ub=14.4 V)
Supply voltage 8–18 V
Sensitivity 760 mV r.m.s.
Input impedance 70 kΩ
Power output 54 W r.m.s. into 4 Ω (f=1 kHz; THD+N=1%)
Harmonic distortion (THD+N) at 1 W into 4 Ω: 0.046% (1 kHz)
0.29% (20 kHz)
at 35 W into 4 Ω: 0.12% (1 kHz)
0.7% (20 kHz)
Signal-to-noise ratio (with 1 W into 4 Ω) 88 dBA
Power bandwidth 7.5 Hz – 185 kHz (at 25 W into 4 Ω)
Quiescent current about 135 mA (‘on’)

COMPONENTS LISTResistors:R1 = 1MΩ
R2 = 4kΩ7
R3 = 1kΩ
R4 = 100kΩ
Capacitors:C1,C2 = 470nF
C3,C4 = 10μF 63V radial
C5,C6,C8 = 4700μF 25V radial
(18mm max. dia., raster 7.5 mm)
C7 = 100nF, raster 5 mm
Semiconductors:
D1 = high-efficiency-LED
IC1 = TDA1562Q (Philips)
Miscellaneous:
S1 = single-pole on/off switch
Four spade connectors, PCB mount
Heatsink for IC1 (Rth<2.5>

Improved 20-LED AUDIO VU METER

This circuit has 3 main sections, an inverting op-amp amplifier, a rectifier and LED display. The input can be from almost any low level source, but if not using an electret microphone, then omit R1 as it's not necessary. The gain of the amplifier based around IC1 is controlled by VR1. The output is rectified by D1,2 and filtered using C4,R6.The final stage is a standard design for the LM3914. Alter R8 to control LED brightness but be careful not to over-drive the IC's. It's recommended that you don't