The aim of this circuit is to demonstrate how we can utilise solar light to electrify the remote areas, i.e., how we can store the solar energy and then use it for small-scale lighting applications.

The DC voltage from the 10W, 12V solar panel is used to charge the battery and control the relay. Capacitor C connected in parallel with a 12V SPDT relay coil remains charged in daytime until the relay is activated. Capacitor C is used to increase the response time of the relay, so switching occurs moments after the voltage across it falls below 12V. The higher the value of the capacitor, the more the delay in switching.

During daytime, relay RL energises, the positive terminal of the battery is connected to the output of regulator IC 7808 (a 3-terminal, 1A, 8V regulator) via diode D and normally-open (N/O) contacts of relay RL1. Here we have used a 6V, 4.5Ah maintenance-free, lead-acid rechargeable battery. It requires a constant voltage of approx. 7.3 volts for its proper charging.
Even though the output of the solar panel keeps varying with the light intensity, IC 7808 (IC1) is used to give a constant output of 8V. Diode D causes a drop of 0.7V, so we get approx. 7.3V to charge the battery.

At night, there will be no generation of electricity. The relay will not energise and charging will not take place. The solar energy stored in the battery can then be used to light up the lamp. A 3W lamp glows continuously for around 6 hours if the battery is fully charged. Instead of a 3W lamp, you can also use a parallel array of serially connected white LEDs and limiting resistors to provide sufficient light for even longer duration.


Solar Home Light Circuit







This is is a stereo power amplifier circuit works up to 22W on each channel. It will be 2x22W output. A few externel components required to support the main component of TDA1554. Heatsink on the power IC is a must to prevent overheating on the power IC. The chip should run cool enough to touch with the proper heatsink installed.Operated at 12 Volts and at about 5 Amps at full volume. Lower volumes use less current, and therefore produce less heat. Printed circuit board is preferred, but universal solder or perf board will do. Keep lead length short.


22 watts amp circuitcomponentssystem view

Hi-Fi 3D Surround Sound System

Surround system let the listener experience the sound reaching from three or more directions, which provides a more realistic audio environment.In fact, surround is the concept of expanding the spatial imaging of audio playback from one dimension(mono/left-right) to two or three dimensions. The surround sound effect can be achieved by processing an existing stereo sound track to add spaciousness and to make it originate it from outside the left/right speaker locations.

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Creating surround sound

Surround sound is created in several ways. The first and simplest method is using a surround sound recording microphone technique, and/or mixing-in surround sound for playback on an audio system using speakers encircling the listener to play audio from different directions. A second approach is processing the audio with psychoacoustic sound localization methods to simulate a two-dimensional (2-D) sound field with headphones. A third approach, based on Huygens’ principle, attempts reconstructing the recorded sound field wave fronts within the listening space; an “audio hologram” form. One form, wave field synthesis (WFS), produces a sound field with an even error field over the entire area. Commercial WFS systems, currently marketed by companies sonic emotion and Iosono, require many loudspeakers and significant computing power.

The Ambisonics form, also based on Huygens’ principle, gives an exact sound reconstruction at the central point; less accurate away from center point. There are many free and commercial software available for Ambisonics, which dominates most of the consumer market, especially musicians using electronic and computer music. Moreover, Ambisonics products are the standard in surround sound hardware sold by Meridian Audio, Ltd. In its simplest form, Ambisonics consumes few resources, however this is not true for recent developments, such as Near Field Compensated Higher Order Ambisonics.[17] Some years ago it was shown that, in the limit, WFS and Ambisonics converge.[18]

Finally, surround sound also can be achieved by mastering level, from stereophonic sources as with Penteo, which uses Digital Signal Processing analysis of a stereo recording to parse out individual sounds to component panorama positions, then positions them, accordingly, into a five-channel field. There are however more ways to create surround out of stereo, for instance with routines based on the QS and SQ Quad routines, where instruments were in the studio divided over 4 speakers. This way of creating surround with software routines is normally referred to as “upmixing”.[19]



230v AC to 12 V DC
3A Transformer, 7812 regulator
IN5408*4 diodes
NJM 2702D-14pin DIP,two channel
TDA 1557Q-13pin SIL,Class B,20W*2, 4 ohm output.

Two channel sounds is the standard format for home stereo receivers,television and FM radio broadcast. When we listen to these two channels on separate speakers, it recreates the experience of being present at the event. Surround recordings can take this idea a step further by adding more audio channels so that the listener experience the sound reaching them from three or more directions which provides more realistic audio environment.


Ultra Low Cost HEARING AID using TDA 2822M Audio Amplifier IC

This low-cost, general-purpose electronic hearing aids works off 3V DC (2×1.5V battery). Transistor T1 and associated components form the audio signal preamplifier for the acoustic signals picked up by the condenser microphone and converted into corresponding electrical signals.

The medium-power amplifier section is wired around popular audio amplifier IC TDA2822M (not TDA2822). This IC, specially designed for portable low-power applications, is readily available in 8-pin mini DIP package. Here the IC is wired in bridge configuration to drive the 32-ohm general-purpose monophonic earphone.

The audio output of this digital hearing aides circuit is 10 to 15 mW and the quiescent current drain is below 1 mA. The circuit can be easily assembled on a veroboard. For easy assembling and maintenance, use an 8-pin DIP IC socket for TDA2822M.

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