Minggu, 15 Juli 2012

electromotive force

Having looked at some of the alternative offerings on the web, I decided it was time to do a series on basic electronics. Most I have seen are either too simplistic, and do not explain each component well enough, or are so detailed that it is almost impossible to know what you need to know as opposed to what you are told you need. These are usually very different. Basic components are not always as simple as they may appear at first look. This article is intended for the beginner to electronics, who will need to know a number of things before starting on even the simplest of projects. The more experienced hobbyist will probably learn some new things as well, since there is a good deal of information here that most non-professionals will be unaware of. This is by no means an exhaustive list, and I shall attempt to keep a reasonable balance between full explanations and simplicity. I shall also introduce some new terminology as I go along, and it is important to read this the way it was written, or you will miss the explanation of each term as it is first encountered. It must be noted that the US still retains some very antiquated terminology, and this often causes great confusion for the beginner (and sometimes the not-so-beginner as well). You will see some "beat-ups" of the US - citizens of same, please don't be offended, but rather complain bitterly to anyone you see using the old terminology. Within The Audio Pages, I use predominantly European symbols and terminology - these are also the recommended (but not mandatory) symbols and terms for Australia, and I have been using them for so long that I won't be changing them. The basic electrical units and definitions are as shown below. This list is not exhaustive (also see the Glossary), but covers the terms you will encounter most of the time. Many of the terms are somewhat inter-related, so you need to read all of them to make sure that you understand the relationship between them.Passive: Capable of operating without an external power source. Typical passive components are resistors, capacitors, inductors and diodes (although the latter are a special case). Active: Requiring a source of power to operate. Includes transistors (all types), integrated circuits (all types), TRIACs, SCRs, LEDs, etc. DC: Direct Current The electrons flow in one direction only. Current flow is from negative to positive, although it is often more convenient to think of it as from positive to negative. This is sometimes referred to as "conventional" current as opposed to electron flow. AC: Alternating Current The electrons flow in both directions in a cyclic manner - first one way, then the other. The rate of change of direction determines the frequency, measured in Hertz (cycles per second). Frequency: Unit is Hertz, Symbol is Hz, old symbol was cps (cycles per second) A complete cycle is completed when the AC signal has gone from zero volts to one extreme, back through zero volts to the opposite extreme, and returned to zero. The accepted audio range is from 20Hz to 20,000Hz. The number of times the signal completes a complete cycle in one second is the frequency. Voltage: Unit is Volts, Symbol is V or U, old symbol was E Voltage is the "pressure" of electricity, or "electromotive force" (hence the old term E). A 9V battery has a voltage of 9V DC, and may be positive or negative depending on the terminal that is used as the reference. The mains has a voltage of 220, 240 or 110V depending where you live - this is AC, and alternates between positive and negative values. Voltage is also commonly measured in millivolts (mV), and 1,000 mV is 1V. Microvolts (uV) and nanovolts (nV) are also used. Current: Unit is Amperes (Amps), Symbol is I Current is the flow of electricity (electrons). No current flows between the terminals of a battery or other voltage supply unless a load is connected. The magnitude of the current is determined by the available voltage, and the resistance (or impedance) of the load and the power source. Current can be AC or DC, positive or negative, depending upon the reference. For electronics, current may also be measured in mA (milliamps) - 1,000 mA is 1A. Nanoamps (nA) are also used in some cases. Resistance: Unit is Ohms, Symbol is R or Ω Resistance is a measure of how easily (or with what difficulty) electrons will flow through the device. Copper wire has a very low resistance, so a small voltage will allow a large current to flow. Likewise, the plastic insulation has a very high resistance, and prevents current from flowing from one wire to those adjacent. Resistors have a defined resistance, so the current can be calculated for any voltage. Resistance in passive devices is always positive (i.e. > 0) Capacitance: Unit is Farads, Symbol is C Capacitance is a measure of stored charge. Unlike a battery, a capacitor stores a charge electrostatically rather than chemically, and reacts much faster. A capacitor passes AC, but will not pass DC (at least for all practical purposes). The reactance or AC resistance (called impedance) of a capacitor depends on its value and the frequency of the AC signal. Capacitance is always a positive value. Inductance: Unit is Henrys, Symbol is H or L (depending on context) Inductance occurs in any piece of conducting material, but is wound into a coil to be useful. An inductor stores a charge magnetically, and presents a low impedance to DC (theoretically zero), and a higher impedance to AC dependent on the value of inductance and the frequency. In this respect it is the electrical opposite of a capacitor. Inductance is always a positive value. The symbol "Hy" is sometimes used in (guess where :-) ... the US. There is no such symbol. Impedance: Unit is Ohms, Symbol is Ω or Z Unlike resistance, impedance is a frequency dependent value, and is specified for AC signals. Impedance is made up of a combination of resistance, capacitance, and/ or inductance. In many cases, impedance and resistance are the same (a resistor for example). Impedance is most commonly positive (like resistance), but can be negative with some components or circuit arrangements. Decibels: Unit is Bel, but because this is large, deci-Bels (1/10th Bel) are used), Symbol is dB Decibels are used in audio because they are a logarithmic measure of voltage, current or power, and correspond well to the response of the ear. A 3dB change is half or double the power (0.707 or 1.414 times voltage or current respectively). Decibels will be discussed more thoroughly in a separate section. A few basic rules that electrical circuits always follow are useful before we start. A voltage of 1V across a resistance of 1 Ohm will cause a current flow of 1 Amp, and the resistor will dissipate 1 Watt (all as heat). The current entering any passive circuit equals the current leaving it, regardless of the component configuration. Electricity can kill you! The danger of electricity is current flowing through your body, not what is available from the source. A million volts at 1 microamp will make you jump, but 50V at 50mA can stop you dead - literally. An electric current flowing in a circuit does not cause vibrations at the physical level (good or bad), unless the circuit is a vibrator, loudspeaker, motor or some other electro-mechanical device. (i.e. components don't vibrate of their own accord unless designed to do so.) External vibrations do not affect the operation of 99.9% of electronic circuits, unless of a significant magnitude to cause physical damage, or the equipment is designed to detect such vibrations (for example, a microphone). Power is measured in Watts, and PMPO does not exist except in the minds of advertising writers. Large capacitors are not intrinsically "slower" than small ones (of the same type). Large values take longer to charge and discharge, but will pass AC just as well as small ones. They are better for low frequencies. Electricity can still kill you, even after reading this article. Some of these are intended to forewarn you against some of the outrageous claims you will find as you research these topics further, and others are simple electrical rules that apply whether we like it or not.
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Function zener

Of the myriad components available to electronic designers, zener diodes are among the handiest and strangest. Similar to normal semiconductor diodes in most respects, they also regulate voltage and are designed to work backwards. Their reliability, low cost and small size make them a good choice when a circuit needs constant voltage. Function zener A zener is a kind of semiconductor diode. As with other diodes, it prefers to conduct current in one direction. Normal diodes have a reverse breakdown voltage; no current will flow opposite to the preferred direction, but if the voltage is more than the breakdown value, current will flow and damage the part. A zener, on the other hand, won't be damaged as long as the current is under the device's limit. Used this way, the voltage across the zener will be a constant value determined by the diode itself. They are commonly available in the range of 1.8 to 200 volts. Identification Being a diode, a zener is a small part with two leads and usually a band on the body indicating polarity. The body may be glass, plastic, or metal. It's hard to tell zeners apart from other diodes, however. The best way of telling is by having the schematic handy, or looking up the part number. Considerations Zeners, like other diodes, can conduct only a limited amount of current. Too much current will cause the diode to short out, which could immediately destroy it. This means they're used in low-current parts of a circuit, such as a voltage reference that controls higher-current-carrying transistors. Expert Insight Being semiconductor diodes, zeners are temperature-sensitive. If it's an issue, good circuit design can compensate for this. Because of competing internal effects that cancel each other out, a 5.6V zener is much less sensitive to temperature than ones with lower or higher voltage ratings. Benefits Some devices, like flashlights, portable radios and toy cars, work fine for a range of voltages. Many electronic circuits, however, need a constant voltage somewhere in the design. Zeners are an easy-to-use, low-cost way of achieving good voltage regulation.
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Sabtu, 14 Juli 2012

Half-wave rectifier

As the rectifier voltage, the diode is used to convert alternating voltage (AC) into DC voltage (DC). Rectifier voltage have 2 kinds, namely: 1. Half-wave rectifier (half-wave rectifier) 2. Full wave rectifier (full-wave rectifier) 1. Half-wave rectifier (half-wave rectifier) When used as a half-wave rectifier, diode voltage direction AC

Rectifiers are often called into action to measure signal strength. Rectify an AC signal, pass it through a low-pass filter and the resulting DC level represents some measure of the signal's magnitude. Although the series diode is the classic rectifier, it can't rectify signals smaller that it own forward voltage! But what if your expected amplitude can be as low as 100 mV? Op amps to the rescue! The advantage of op amp circuits lies in their ability to compensate for non-linear devices in the feedback loop. Combining the rectifying action of a diode with the accuracy of an op amp, this circuit creates a precision rectifier.

Half-wave rectifier (half-wave rectifier)
When used as a half-wave rectifier, diode menyearahkan shaped AC voltage into DC voltage sine wave only during the positive cycle of AC voltage only. Meanwhile, during the negative cycle, the diode having panjaran back (reverse bias) so that the load voltage (output) to zero.

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Electrical inductance sensors are non-contact devices that measure the inductance of an electrical component or system. They consist of a wire loop or coils and are relatively inexpensive. Inductance, the property of a circuit or circuit element to oppose a change in current flow, refers to the capacity of a conductor to produce a magnetic field. The standard unit of inductance is the Henry (H). Because the Henry is a large unit, electrical inductance sensors often measure inductance in microhenry (µH) or millihenry (mH) levels.

Electrical inductance sensors contain a nickel-iron core shaft that rotates within the coil around the material. The inductance measured by an electrical inductance sensor depends on the number of turns in the coil, the type of material around which the coil rotates, and the radius of the coil. With the rotation of the shaft, displacement occurs within the coil and generates inductance. This displacement produces signals that can be measured by an inductance meter and recorded. Most inductance meters are digital, hand held devices suitable for measuring inductance of very low value. The results of the inductance calculation can be plotted as a graph for future study.

Selecting electrical inductance sensors requires a careful analysis of product specifications and application requirements. Most electrical inductance sensors have a standard accuracy variance of less than 0.5% when measured on full scale. For best results, an electrical inductance sensor should be able to generate an output signal of at least 4-20 mA. Typically, a sensor’s measurement range is approximately 30% of the coil diameter. For high precision measurements, the thickness of the coil should be at least 0.025 inches (in.).

Electrical inductance sensors are used in many different applications. Some electrical sensors are used in the automotive industry and the power industry. Other electrical sensors are used in constructing planar transformers, generating electrical magnetic fields, and monitoring the inductance of an electrical component. Electrical sensors such as electrical inductance sensors are widely used for detecting the presence of electrical voltage in equipments, and defective gro
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Antenna diplexer

Antenna diplexer
- A brief overview, a tutorial on the basics of antenna or RF diplexer diplexer used for purposes including enabling a single RF antenna for use by several transmitters ..

An antenna or RF diplexer diplexer is a unit in a single application can be used to allow more than one transmitter to operate on a single RF antenna. Sometimes these units can be called antenna duplexers. Typically an antenna diplexer will allow the transmitter to a different frequency operation using the same antenna. In other applications, an antenna diplexer can be used to allow a single antenna to be used for transmission on one frequency band and receiving on other bands.

Antenna diplexers find many uses. In one common example of an antenna or RF diplexer diplexer used in cellular base station to allow it to send and receive simultaneously. The diplexer antenna allows the system to use the same antenna while preventing the transmitted signal from reaching the receiver and the input block. In other applications diplexer may be used by broadcast stations transmitting at different frequencies at the same time using the same antenna. Use of diplexer allows a single antenna to be used, while preventing the output of a transmitter which fed back into the other output.

Diplexers small antennas can be used in a domestic environment to enable multiple signals to run along a single feeder. In one application may allow a single feeder to be used for television and VHF FM radio reception, or to allow television signals from terrestrial and satellite voice box low (LNB) to pass on the same lead. This RF diplexers are usually relatively low cost as not nearly as demanding specifications that are used for professional installation of the RF diplexer.

Basic concept of antenna diplexer

There are a number of ways to implement the RF diplexers. They all involve the use of filters. In this way the path to a different transmitter and receiver can be separated according to the frequency they use. The easiest way to implement the diplexer is to use low pass and high pass filter despite the band-pass filter can be used. In this way diplexer routes all signals at frequencies below the cut-off frequency of low pass filter to one port, and all signals above the cut-off frequency high pass filter to another port. Also here are the street from between two long-distance from the filter. All the signals that can pass through low pass filter in the diplexer will not be able to pass through a high pass filter and vice versa.
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microcontroller chips

microcontroller chips appear on the market, today’s microcontroller programming tools are becoming more and more ‘universal’ to cope with different programming conventions. It is also sadly the case that the more ‘universal’ the programmer, the more you need to pay. In practice, most people will only use a fraction of the capabilities of such a programmer, making it difficult to justify such an expense. The project here describes a minimal solution to the programming problem for one of the most popular types of controller. The PIC16F84 (1k-Flash-memory) and the PIC16C84 (1k-ROM) with 13 I/O-lines.

Using a PC together with this relatively simple interface and some software it is possible to build a low cost programmer The design for the programmer is described on the author’s website. The programmer connects to the serial port of a PC. Pin 3 of the port supplies the power and zener diode D6 along with D5 regulates the supply to the chip at 5 V. C1 and C2 smooth the regulated supply. The unregulated supply is fed to pin MCLR of the PIC to configure it in programming mode. R1 limits current into this pin and an internal regulator ensures the correct programming voltage on chip. A high on this pin switches the PIC into programming mode.

Data exchange between the PC and the PIC occurs over the lines TxD (Pin 3), DTR (Pin 4) and CTS (Pin 8) and can be viewed on the LEDs D2, D3 and D4. A control software package comprising NTPICPROG, PIX and Euro13 for Windows and DOS (altogether 198 kB) can be downloaded free from the ‘Elektro’ page of the authors website at
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The KIA555P monolithic circuit is a highly stable device for producing accurate time delay or timing pulse. Additional terminals are provided for triggering or resetting if desired. In the time delay or monostable mode of operation, the time is precisely controlled by one external resistor and capacitor. In the astable mode of operation, the frequency and duty cycle are accurately and independently controlled with two external resistors and one capacitor. The circuit of the KIA555P may be triggered and reset on falling waveforms, and the output structure and source and sink up to 200mA or drive TTL circuit. Operation is specified for supplies of 5-15V. Features: Timing from Microseconds Through Hours Operates in both astable and monostable modes Output can source or sink 200mA Output TTL compatible Temperature stability of 0.005%/ °C typ Normally On or Normally Off output