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20W audio amplifier using LM1875

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This is just another 20W audio amplifier circuit , but this time based on the LM1875 audio amplifier IC from National Semiconductors. With a 25V dual power supply LM1875 can deliver 20W of audio power into a 4 ohm speaker. The LM1875 requires very less external components and has very low distortion. The IC is also packed with a lot good features like fast slew rate, wide supply voltage range, high output current, high output voltage swing, thermal protection etc. The IC is available in TO-220 plastic power package and is well suitable for a variety of applications like audio systems, servo amplifiers, home theatre systems etc.
Read more: http://www.circuitstoday.com/20w-audio-amplifier-using-lm1875#ixzz11VTC9Fzh
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All about Solar Panels

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I hope to cover this article with the following. Don’t know I have succeed in this.

What are solar panels?
How do solar panels work?
How to make panels?

Solar Panels use arrays of solar photovoltaic cells to convert incoming photons from sun into usable electricity. With solar panels we are using echo friendly renewable energy from the sun.

Solar panels are typically constructed with crystalline silicon, and the more expensive gallium arsenide, which is produced exclusively for use in photovoltaic (solar) cells.

Other, more efficient solar panels are assembled by depositing amorphous silicon alloy in a continuous roll-to-roll process. The solar cells created from this process are called Amorphous Silicon Solar Cells, or A-si. Solar Panels constructed using amorphous silicon technology is more durable, efficient, and thinner than their crystalline counterparts.

For very important solar projects, such as space probes, very-high efficiency solar cells are constructed from gallium arsenide by a process called molecular beam epitaxy. Solar cells constructed by this process have several p-n junction diodes, each designed to be maximally efficient at absorbing a given part of the solar spectrum. These solar panels are much more efficient than conventional types, but the process and materials involved make them far too expensive for everyday applications.

Solar panels collect solar radiation from the sun and actively convert that energy to electricity. Solar panels are comprised of several individual solar cells. These solar cells function similarly to large semiconductors and utilize a large-area p-n junction diode. When the solar cells are exposed to sunlight, the p-n junction diodes convert the energy from sunlight into usable electrical energy. The energy generated from photons striking the surface of the solar panel allows electrons to be knocked out of their orbits and released, and electric fields in the solar cells pull these free electrons in a directional current, from which metal contacts in the solar cell can generate electricity. The more solar cells in a solar panel and the higher the quality of the solar cells, the more total electrical output the solar panel can produce. The conversion of sunlight to usable electrical energy has been dubbed the Photovoltaic Effect. The photovoltaic effect arises from the properties of the p-n junction diode; as such there are no moving parts in a solar panel.

Lead-acid storage battery

History of Lead Acid Battery

The lead-acid storage battery, an important energy storage device, is the most widely used secondary storage cell by automobile and other industries. Storage cells are devices which release a flow of electron through an external circuit as a result of reactions occurring between the active electrode materials and ions transported by the electrolyte. The cells in which the reactions are reversible are called secondary cells. In these cells the active materials can be returned to their original state by applying electrical current from an external source in the opposite direction to the flow of the cells discharge current.

In the early nineteenth century, scientists discovered that when direct current was passed between some pairs of electrodes of the same metal immersed in an electrolyte, the electrodes became polarized, i.e. when the circuit was opened a difference of potential existed between the electrodes. If they were connector, together a current flowed. Based on these experiments, in 1959

Gasten Plant began to investigate such cell using two electrodes immersed in dilute sulfuric acid. He found that appreciable currents could be obtained from the cell, after it was charged to produce a coating of lead peroxide on the positive plate. This was a major breakthrough in the field of electro chemistry.

Since then major developments have taken place in basic material of construction of lead-acid batteries. The present construction of this type of battery consists of positive electrode made up of leap peroxide, negative electrodes of lead in highly active metallic sponge. The insulating layers are made of hard rubber, PVC etc. The electrolyte is a dilute aqueous solution of sulphuric acid and container is marie of plastic, glass, rubber or polypropylene.

In 1940's six volt rubber case, featuring external cell connectors were available. Ford company offered codar separators and thirteen percent (13%) antimony grid alloys. The battery had a temperature compensating,vibrating contact voltage regulator. By the end of the 50's twelve volt battery was available featuring rubber separators and seven percent antimony in the grid alloy.

Towards the end of the 60's, the typical new car battery featured, through partition connectors, one piece cover, and sealed side terminals, a rubber container and grid alloy containing four percent antimony. Some of the leading battery manufacturers also introduced polypropylene containers at that time.

During the latter half of 70's the battery industry entered the maintenance free era. Grids with 1-2% antimony and other alloya like Ca, sn and plates made by high speed continuous strip processing equipment were introduced. In place of conventional separators plates, encapsulated in plastic envelopes came as new technology. The polypropylene container became a cocoon, completely sealing the battery against entry and containing subsystems, such as build-in state of charge indicators, and flame arresting vent system. In early 80's major changes tookplace in the technology of manufacturing systems, like continuous automatically controlled casting, rolling,grid expansion, pasting, curing cutting and stacking of battery plates.. This enhanced the roduction rates to a level undreamed of ten years earlier. In the modern plants up above the plate line, active material ingredients are programmed, weighed, and blended by computer controlled paste mixers, resulting in control of plate weight, thickness and chemistry, which was not possible few years ago. Control of this production system is backed up by analytical equipment, such as the atomic absorption spectrograph, florescent xray spectrometers, particle distribution counter and optical emission spectrograph. Sophisticated welding machines are common in all battery plants in USA, UK, Canada and France.

At present a great deal of emphasis is on the need of smaller and lighter batteries, for new small sized car and automobiles. The drive for improved fuel economy and the space limitations of present and planned engine compartments, are still strong factors today for the development of small, light weight, high powered batteries.

Chemical Reaction
Batteries use a chemical reaction to do work on charge and produce a voltage between their output terminals.

The reaction of lead and lead oxide with the sulfuric acid electrolyte produces a voltage. The supplying of energy to and external resistance discharges the battery.

The discharge reaction can be reversed by applying a voltage from a charging source.
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ISP Flash Microcontroller Programmer

Introduction

This ISP Programmer can be used either for in-system programming or as a stand-alone spi programmer for Atmel ISP programmable devices. The programming interface is compatible to STK200 ISP programmer hardware so the users of STK200 can also use the software which can program both the 8051 and AVR series devices.

Hardware

Figure 1 shows the circuit diagram of the in-system programmer interface, the power to the interface is provided by the target system. The 74HCT541 ic isolate and buffer the parallel port signals. It is necessary to use the HCT type ic in order to make sure the programmer should also work with 3V type parallel port.


More information (PCB, descriptions, Programmer software can be found at the following Link)
Link to main site

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Single chip(MAX 2606) based FM transmitter circuit

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Here’s a single chip FM transmitter circuit using Maxim semiconductors IC MAX2606. The MAX2606 is a compact, high-performance intermediate frequency VCO specially designed for wireless communication circuits. They have monolithic construction with low-noise and a low-power operation in a compact 6-pin SOT23 packing .Th1s low-noise IC feature an on-chip varicap diode and feedback capacitances that avoid the need for external tuning components, making the MAX2606 perfect for portable systems. Only an external inductor is needed to set the oscillation frequency.In addition to this, an
integrated differential output buffer is also there for driving a mixer or prescaler.The MAX2606 can be operated from a single +2.8 V to +5.4V supply and consumes very less current .The chip can be operated from 45MHz to 650MHz .

In the circuit the nominal frequency is set to 100 Mhz by inductor L1, (390nH) . The left and right channel audio signals from your source are added by R3 and R4, and attenuated by the POT R2. R2 can be used as a volume control .POT R1 can be used to select a channel of transmission between 88Mhz and 108Mhz.Use 80 cm long wire as the antenna .

Notes

• Assemble the circuit on a good quality PCB or common board.
• Use a battery for powering the circuit.It will reduce noise.
• An FM antenna from a old radio is a better option than the wire antenna.

The output is between 88MHz and 108MHz, and allows transmitting audio signals to FM radios for remote listening. A schematic is provided with all component values to complete the project. Output power is ~ -21dBm, and the IC operates on 3V.

IC1 is a voltage-controlled oscillator with integrated varactor. Its nominal frequency of oscillation is set by inductor L1, and a 390nH value places that frequency at 100MHz. Potentiometer R1 then lets you select a channel by tuning over the FM band of 88MHz to 108MHz. Output power is about -21dBm into 50 (most countries accept emissions below 10dBm in the FM band).

The audio unit's left and right audio signals are summed by R3 and R4, and attenuated by the (optional) potentiometer R2. R2's wiper signal serves as a volume control by modulating the RF frequency. Signals above 60mV introduce distortion, so the pot attenuates down from that level.

In the absence of a standard FM radio antenna, 75cm (30 inches) of wire will suffice as a transmitting antenna. For best reception, it should be mounted parallel with the receiving antenna. The IC operates on a single supply voltage in the range 3V to 5V, but one must regulate the applied voltage to minimize frequency drift and noise.