The famous transistor cross reference book is the Philip ECG semiconductor master replacement guide. In the content you can find all kind of electronic components specification and ic schematic too. It is one of the must ‘have’ semiconductor guide for those who love electronic troubleshooting. The internal diagram or layout of ic is clearly drawn and the transistor parameters were also listed in this book. The price of this guide is not expensive and as an electronic repairer you should buy one. Just imagine without this book, you will be facing difficulty finding the right component for substitution.

In this book, many types of transistor data and specification were listed such as the bipolar transistor, silicon controlled rectifier, fet field effect transistor (Mosfet), junction field effect transistor (jfet), signal transistors, high voltage transistor such as the horizontal output transistor (HOT), silicon power transistor, surface mounted transistor, digital transistor and many other types. Although you can find a substitution part number from the normal transistor data guide book, the ECG philips master replacement book is more informative. The normal transistor replacement book only provide the voltage (v), current (amp) and wattage (w) rating for HOT but the ECG master equivalent guide show beyond than that such as the frequency , current gain (hfe) and the outlook too . Other than HOT, the normal transistor data book gives a superb or quite accurate comparison part number for you to refer.

There is one secret that I want to share to you about transistor cross reference equivalent. If you are searching substitution part number for a signal transistor, a higher voltage, ampere, and wattage will be enough but not in the case if you want to find a substitution part number for horizontal output transistor (HOT). Higher voltage, ampere and wattage will not always work because there is few more parameter that you need to take into consideration. You may ask why the transistor blow even if it has a higher voltage, higher current and higher wattage compare to the original one.

The other parameter that you need to see is the switching time which we call it the storage and fall time. Different HOT have different spec, if you really want to find a substitution for HOT, make sure you check out the storage and fall time parameter besides the higher voltage, current and wattage rating. Searching the internet for the components specification is easy-just type in the component part number follow by datasheet, data sheet, specification, spec, data, equivalent, part number, identification, marking, pinout, types, codes and cross reference. Usually the manufacturer’s website will appear and follows by other electronic supplier website. Click on the websites that you think is relevant to your search and hope you will get what you are searching.

As for the above secret, actually I have tested on quite a numbers of Monitor with the storage and fall time slightly out from the original parameter. After the replacement, the Monitor works fine but only for a very short period before it gets very hot. If I continue to let the Monitor run, I believe the HOT will blow! When I replaced the HOT with another equivalent part number that have the specification about the same as the original one, (especially the storage and fall time), the Monitor run perfectly well. My rule of thumb is, always get the exact part number first before using other number that you found from transistor cross reference book.

Another method that is used in some Repair Centers involves a Test lamp, a battery and a few Test leads. The lamp and battery are connected in Series then placed across the SCR’s Anode and Cathode leads (the negative lead of the battery connects to the SCR’s Cathode lead). A flying test lead is then used to trigger the SCR by momentarily connecting the positive terminal of the battery to the SCR’s gate lead.

Both of these Test methods can provide an indication of device functionality when no other methods are available. Unfortunately, both methods require the Technician to consult a Datasheet or Service Manual prior to Testing the SCR. This ensures correct lead configuration. If the device pinout can not be determined, then the whole Test process becomes little more than a guess, or a hit-and-miss operation.

Failure analysis or Functional Test of the SCR should always be performed when the device is out of circuit. This means that the component should not be electrically connected to anything other than the Test Equipment that is used to evaluate the devices functionality.

At a well equipped Repair Center, SCR’s are tested utilizing an SCR Component Analyzer. This equipment confirms the SCR’s functionality, by gating the device and intelligently measuring its device characteristics. Confirm that the device tests as follows:

Press the Red Test Button to turn the Component Analyzer on. The Blue Result LED will light. Attach the Test Leads to the SCR’s Gate, Cathode and Anode Terminals. It is not important which leads go where. The Component Analyzer will determine the connection details.

Press the Red Test Button. The first three LED’s will display the connection details for a functional device. The Result LED will display the Test result. A Blue LED means that the device has an open circuit condition. A Red LED means that the device is shorted. A Green LED means that the device is Functional.

SCR consists of three pin of Gate (G), Anode (A) and Cathode (C). In order to identify the pin out, one must find it from semiconductor data book such the famous Philips ECG master semiconductor replacement guide. The data book will list out the general specification of the SCR such as the volt and ampere. If you want to know more details about a particular SCR, you can always try to search from the internet. Usually the SCR manufacturers will provide the full datasheet for those who want it.

Once you know the pin outs of the G, A and C legs you can begin to test the SCR. If you have the Peak electronic atlas component analyzer tester, what you need to do is to connect the three small clips to each pin of the SCR (any part number will do). The tester will begin to analyze the SCR and prompt you with the display such as “Sensitive or low power thyristor” before it tells you the exact pin outs of G, A and C. After the first test, the tester will eventually show you the answer at the LCD display. Red is Gate, Green is Cathode and Blue is Anode. It is a simple process and you will know the answer in less than 10 seconds. If there is a problem in the SCR, the tester would not be able to show the results instead it shows a shorted reading.

If you don’t have this tester for checking SCR, I’m showing you another easy way on how to test SCR fast. You need an analog meter set to X1 ohm. Place the red probe to the Cathode and black probe to the Anode pin. At this time the meter doesn’t show any reading. Now gently move the black probe and touch the Gate pin (the black probe still touching the Anode pin) and you will notice the meter’s pointer will kick as shown at the picture (low resistance).

Removing the black probe from the GATE pin (the black probe still touching the Anode pin) you would noticed that the resistance continues to be there (low resistance). This is due to the conduction of SCR as the meter battery is usually able to supply current more than the holding current. If at this stage you removed the black probe from the Anode pin and connect it back, the pointer will dropped back to infinity (high resistance). If the SCR could hold the resistance then the SCR is considered good. If it can’t hold then the SCR is faulty.

Conclusion- Practice testing SCR more often to see how’s the result like. Try some different part numbers and power SCR-and if the resistance don’t hold using X1 ohm, you may try X10 ohm and etc.

The boards are also used to electrically connect the required leads for each component using conductive copper traces. The component pads and connection traces are etched from copper sheets laminated onto a non-conductive substrate. Printed circuit boards are designed as single sided with copper pads and traces on one side of the board only, double sided with copper pads and traces on the top and bottom sides of the board, or multilayer designs with copper pads and traces on top and bottom of board with a variable number of internal copper layers with traces and connections.

Single or double sided boards consist of a core dielectric material, such as FR-4 epoxy fiberglass, with copper plating on one or both sides. This copper plating is etched away to form the actual copper pads and connection traces on the board surfaces as part of the board manufacturing process. A multilayer board consists of a number of layers of dielectric material that has been impregnated with adhesives, and these layers are used to separate the layers of copper plating. All of these layers are aligned and then bonded into a single board structure under heat and pressure. Multilayer boards with 48 or more layers can be produced with today’s technologies.

In a typical four layer board design, the internal layers are often used to provide power and ground connections, such as a +5V plane layer and a Ground plane layer as the two internal layers, with all other circuit and component connections made on the top and bottom layers of the board. Very complex board designs may have a large number of layers to make the various connections for different voltage levels, ground connections, or for connecting the many leads on ball grid array devices and other large integrated circuit package formats.

There are usually two types of material used to construct a multilayer board. Pre-preg material is thin layers of fiberglass pre-impregnated with an adhesive, and is in sheet form, usually about .002 inches thick. Core material is similar to a very thin double sided board in that it has a dielectric material, such as epoxy fiberglass, with a copper layer deposited on each side, usually .030 thickness dielectric material with 1 ounce copper layer on each side. In a multilayer board design, there are two methods used to build up the desired number of layers. The core stack-up method, which is an older technology, uses a center layer of pre-preg material with a layer of core material above and another layer of core material below. This combination of one pre-preg layer and two core layers would make a 4 layer board.

The film stack-up method, a newer technology, would have core material as the center layer followed by layers of pre-preg and copper material built up above and below to form the final number of layers required by the board design, sort of like Dagwood building a sandwich. This method allows the manufacturer flexibility in how the board layer thicknesses are combined to meet the finished product thickness requirements by varying the number of sheets of pre-preg in each layer. Once the material layers are completed, the entire stack is subjected to heat and pressure that causes the adhesive in the pre-preg to bond the core and pre-preg layers together into a single entity.

The process of manufacturing printed circuit boards follows the steps below for most applications:

Basic Steps for Manufacturing Printed Circuit Boards:

1. Setup – the process of determining materials, processes, and requirements to meet the customer’s specifications for the board design based on the Gerber file information provided with the purchase order.

2. Imaging – the process of transferring the Gerber file data for a layer onto an etch resist film that is placed on the conductive copper layer.

3. Etching – the traditional process of exposing the copper and other areas unprotected by the etch resist film to a chemical that removes the unprotected copper, leaving the protected copper pads and traces in place; newer processes use plasma/laser etching instead of chemicals to remove the copper material, allowing finer line definitions.

4. Multilayer Pressing – the process of aligning the conductive copper and insulating dielectric layers and pressing them under heat to activate the adhesive in the dielectric layers to form a solid board material.

5. Drilling – the process of drilling all of the holes for plated through applications; a second drilling process is used for holes that are not to be plated through. Information on hole location and size is contained in the drill drawing file.

6. Plating – the process of applying copper plating to the pads, traces, and drilled through holes that are to be plated through; boards are placed in an electrically charged bath of copper.

7. Second Drilling – this is required when holes are to be drilled through a copper area but the hole is not to be plated through. Avoid this process if possible because it adds cost to the finished board.

8. Masking – the process of applying a protective masking material, a solder mask, over the bare copper traces or over the copper that has had a thin layer of solder applied; the solder mask protects against environmental damage, provides insulation, protects against solder shorts, and protects traces that run between pads.

9. Finishing – the process of coating the pad areas with a thin layer of solder to prepare the board for the eventual wave soldering or reflow soldering process that will occur at a later date after the components have been placed.

10. Silk Screening – the process of applying the markings for component designations and component outlines to the board. May be applied to just the top side or to both sides if components are mounted on both top and bottom sides.

11. Routing – the process of separating multiple boards from a panel of identical boards; this process also allows cutting notches or slots into the board if required.

12. Quality Control – a visual inspection of the boards; also can be the process of inspecting wall quality for plated through holes in multilayer boards by cross-sectioning or other methods.

13. Electrical Testing – the process of checking for continuity or shorted connections on the boards by means applying a voltage between various points on the board and determining if a current flow occurs. Depending upon the board complexity, this process may require a specially designed test fixture and test program to integrate with the electrical test system used by the board manufacturer.

System Design: This stage provides the specifications and main operations of the chip. It examines such issues like chip area, power, functionality, speed, cost and other design factors while setting these specifications. Sometimes, the resources available to the designer could act as a constraint during this stage. For instance, a designer may like to design a chip to work at 1.2V, but available process technology can only support a voltage of 5V. In this situation, the designer has to adjust these specifications to satisfy the available tools. It is always a good habit to understand the process technology available before system design and specifications.

Process technology is basically the specific foundry technology rules where the chip would be fabricated. Typical examples are AMI 0.5um, TSMC 0.35um and IBM 0.13um. A design based on one process technology is unique to that process and accordingly should be fabricated in a foundry that supports that process. At the system design level, the main sections of the system are illustrated with block diagrams, with no details on the contents of the blocks. Only the input and output characteristics of the sections are detailed.

Logic Design: At this stage, the designer implements the logic networks that would realize the input and output characteristics specified in the previous stage. This is generally made of logic gates with interconnecting wires that are used to realize the design.

Circuit Design: Circuit design involves the translation of the various logic networks into electronic circuitries using transistors. These transistors are switching devices whose combinations are used to realize different logic functions. The design is tested using computer aided design (CAD) tools and comparisons are made between the results and the chip specifications. Through these results, the designer could have an idea of the speed, power dissipation, and performance of the final chip. An idea of the size of the chip is also obtained at this stage since the number of transistors would determine the area of the chip. Experienced designers optimize many design variables like transistor sizes, transistor numbers, and circuit architecture to reduce delay, power consumption, and latency among others. The length and width of the transistors must obey the rules of the process technology.

Layout Design: This stage involves the translation of the circuit realized in the previous stage into silicon description through geometrical patterns aided by CAD tools. This translation process follows a process rule that specifies the spacing between transistors, wire, wire contacts, and so on. Violation of these rules results to malfunctioning chips after fabrication. Besides, the designer must ensure that the layout design accurately represents the circuit design and that the design is free of errors. CAD tools enable checks for errors and also incorporate ways of comparing layout and circuit designs provided in form of Layout Versus Schematic (LVS) checks. When errors are reported, the designer has to effect the corrections.

A vital fundamental stage in layout design is Extraction, which involves the extraction of the circuit schematic from the layout drawings. The extracted circuit provides information on the circuit elements, wires, parasitic resistance and capacitance (a parasitic device is an unbudgeted device that inserts itself due to interaction between nearby components). With the aid of this extracted file, the electronic behavior of the silicon circuit is simulated and it is always a good habit to compare the results with the system specification since this is one of the final design stages before a chip is sent to the foundry.

Fabrication: Upon satisfactory verification of the design, the layout is sent to the foundry where it is fabricated. The process of chip fabrication is very complex. It involves many stages of oxidation, etching, photolithography, etc. Typically, the fabrication process translates the layout into silicon or any other semiconductor material that is used. The result is bonded with pins for external connections to circuit boards.

Fabrication process uses photolithographic masks, which define specific patterns that are transferred to silicon wafers (the initial substrate used to fabricate integrated circuits) through a number of steps based on the process technology. The starting material, the wafer, is oxidized to create insulation layer in the process. It is followed by photolithographic process, which involves deposition of photoresist on the oxidized wafer, exposure to ultra-violet rays to form patterns and etching for removal of materials not covered by photoresist. Ion implantation of the p+ or n+ source/drain region and metallization to form contacts follow afterwards. The next stage is cutting the individual chip from the die.

For external pin connection, bonding is done. It is important to emphasize that this process steps could be altered in any order to achieve specific goals in the design process. In addition, many of these functions are done many times for very complex chips. Over the years, other methods have emerged. A notable one is the use of insulators (like sapphire) as starting materials instead of semiconductor substrate (the silicon on which active devices are implanted) to build the transistors. This method called Silicon on Insulator (SOI) minimizes parasitic in circuits and enable the realization of high speed and low power dissipation chips.

Testing: The final stage of the chip development is called testing. Electronic equipment like oscilloscopes, probes, pattern generators and logic analyzers are used to measure some parameters of the chip to verify its functionalities based on the stated specifications. It is always a good habit to test for various input patterns for a fairly long time in order to discover possible performance degradation, variability, or failures. Sometimes, fabricated chip test results deviate from simulated results. When that occurs, depending on application, the designer could re-engineer the circuit for improvement and error corrections. The new design should be fabricated and tested at the end.

Compared with discrete circuits, integrated circuit’s reliability, mass production capability, and building-block approach to circuit design ensured its adoption. Microprocessors or cores are the most advanced part of an integrated circuit. They control everything. The Random Access Memory is the most regular type of microchip, the highest density devices are thus memories, even a microprocessor will have memory on the chip. The structures are intricate since The layers are much thinner than the device with widths that have been shrinking for years.

Like other intellectual properties, ICs are the essence of human wisdom. They are utilized in a lot of products like television sets, watches, washing machines, automobiles, etc.. There is a continuing need for the creation of new designs that reduce the dimensions of existing integrated circuits and increase their functions at the same time. The smaller an integrated circuit is, the less the material needed for manufacture, and the fewer space needed to accommodate it.

Silicon is the most widely used material in designing a chip because it’s easy to process and has the perfect temperature range for electrical devices, as a matter of fact, it is used for almost every component of the IC. Though elements like gallium arsenide are applied to specialized areas like LEDs, lasers, solar cells and the highest speed integrated circuit.

To allowing more circuitry to be packed on each chip, ICs have consistently migrated to smaller feature sizes over the years. This increased capacity per unit area can be used to decrease cost and increase functionality. As the size shrinks, almost everything improves, like the cost per unit and the switching power consumption go down, the speed goes up. However,every coin has two size, troubles also come into being, although these problems are not solved now and will likely be done at last in the future.

The typical RFID tag has a microchip attached to a radio antenna that is mounted on a substrate. Each chip can store up to 2 kilobytes of data. The data stored can be retrieved by a reader, which has its own antennas emitting radio waves that then receive signals back from the tag. The information picked up by the reader is transferred to the host computer in digital form. The host computer uses this information in various ways. Their biggest applications are in the field of asset tracking and for supply chain mangement.

RFID Technology eases the process of automatic data capturing and brings multiple benefits to applications in which it is used:

• Though expensive, they last longer and deliver value for money with greater data storage capacity
• There are no positioning problems with an RFID tag, they can be placed anywhere and do not even require a line-of-sight to be scanned.
• RFID tags are more robust and secure that can operate in harsh climates and tough environments
• They help to reduce misplacement of goods since they become easier to trace.
• They enhance product visibility which facilitates operations
  The information stored on the RFID tag can be constantly and repeatedly updated
• RFID tags have a longer read range and therefore make more sense on the factory floor where they can be scanned from forklifts and scanners at a distance
• They help to reduce human errors
• It is difficult to duplicate an RFID tag while other identification methods are easier to copy.

RFID technology has been constantly evolving for the last fifty years. Despite all its benefits, one reason why it has taken time to be applied for applications is the lack of standards in the industry. Moreover, reader and tag collision are other problems faced in RFID applications. Reader collision takes place when the signals from two or more readers overlap, and the tag is not equipped to respond to two or more queries simultaneously. Tag collision takes place when there are too many tags within a small area. However, these can be easily avoided to reap the host of other benefits provided by this technology.

Barcode Scanners are now found in each and every industry, they are used to track stock and check the products that are moving in and around your premises, selecting a Barcode scanner will be determined by your needs. With the amount of different varieties offered, it can be a tough choice deciding on the best one for you. Probably the most favored is the Symbol LS2208, it’s good value may last for years and will never fail.

Purpose of Radio frequency Identification and Detection system is to facilitate data transmission through the portable device known as tag that is read with the help of RFID reader; and process it as per the needs of an application. Information transmitted with the help of tag offers location or identification along with other specifics of product tagged – purchase date, color, and price. Typical RFID tag includes microchip with radio antenna, mounted on substrate.

The RFID tags are configured to respond and receive signals from an RFID transceiver. This allows tags to be read from a distance, unlike other forms of authentication technology. The RFID system has gained wide acceptance in businesses, and is gradually replacing the barcode system.

Working

Basic RFID consists of an antenna, transceiver and transponder. Antenna emits the radio signals to activate tag and to read as well as write information to it. Reader emits the radio waves, ranging from one to 100 inches, on the basis of used radio frequency and power output. While passing through electronic magnetic zone, RFID tag detects activation signals of readers.

Powered by its internal battery or by the reader signals, the tag sends radio waves back to the reader. Reader receives these waves and identifies the frequency to generate a unique ID. Reader then decodes data encoded in integrated circuit of tags and transmits it to the computers for use.

Types of RFID

Active and passive RFID are different technologies but are usually evaluated together. Even though both of them use the radio frequency for communication between tag and reader, means of providing power to tags is different. Active RFID makes use of battery within tag for providing continuous power to tag and radio frequency power circuitry. Passive RFID on the other hand, relies on energy of radio frequency transferred from reader to tag for powering it.

Passive RFID needs strong signals from reader but signal strength bounced from tag is at low levels. Active RFID receives low level signals by tag but it can create higher level signals to readers. This type of RFID is constantly powered, whether in or out of the reader’s field. Active tags consist of external sensors for checking humidity, temperature, motion as well as other conditions.

RFID frequencies

Just like you can tune a radio in various frequencies for listening to different channels, RFID readers and tags need to be tuned in to a same frequency for communication. RFID system uses various frequencies but most common and popularly used frequency is low, high and ultra high frequency. Low frequency is around 125 KHz, high is around 13.56 MHz and ultra high varies between 860-960 MHz. Some applications also make use of microwave frequency of 2.45 GHz. It is imperative to choose right frequency for an application as radio waves work different at various frequencies.

History and key developments

RFID has been around since II World War but was viewed as too limited and expensive in functionality for most of commercial use. With advancement in technology, cost of system components has reduced and capabilities have increased, making RFID more popular.

Léon Theremin invented a surveillance tool for Soviet Union in the year 1945. This tool retransmitted the incident radio waves along with audio information. Sound waves vibrated diaphragm that altered the shape of resonator, modulating reflected sound frequencies. This tool was not identification tag but a secret listening device. But it is still considered as predecessor of the RFID technology due to it being energized, passive and stimulated by outside electromagnetic waves. Similar technology as IFF transponder was invented in UK in the year 1915 and was regularly used by allies in the II World War for identifying aircrafts as foes or friends. The transponders are used for by powered aircrafts till date.

Invented in 1973, device by Mario Cardullo is known to be a true ancestor of the modern RFID. Initially the device was passive and was powered by interrogating signals and had transponder 16 bit memory for application as toll device. The basic patent by Cardullo covers application of RF, light and sounds as the transmission media.

Early exhibition of the reflected power RFID tags, semi passive and passive was presented by Robert Freyman, Steven Depp and Alfred Koelle. This portable system used around 12 bit tags and worked at 915 MHz. And the first patent associated with abbreviation of RFID was approved to Mr. Charles Walton in the year 1983.

RFID uses

The role of RFID is not just confined to Aircraft identification anymore; it is also lending a hand in various commercial uses. Asset tracking is one of the most popular uses of RFID. Companies are using RFID tags on the products that might get stolen or misplaced. Almost each type of Radio frequency Identification and Detection system can be used for the purpose of asset management.

Manufacturing plants have also been using RFID from a long time now. These systems are used for tracking parts and working in process for reduction of defects, managing production of various versions and increasing output. The technology has also been useful in the closed looped supply chains for years. More and more companies are turning to this technology for tracking shipments among the supply chain allies. Not just manufacturers but retailers also are using this RFID technology for proper placement of their products and improvements in the supply chain.

RFID also plays an important role in the access and security control. The newly introduced 13.56 MHz RFID systems provide long range readings to the users. The best part is that RFID is convenient to handle and requires low maintenance at the same time.

Comparison with bar codes

RFID definitely has an edge over conventional technology of bar codes. RFID reader easily pulls data from tag at greater distances as compared to barcodes. Range in case of RFID is around 300 feet as against 15 feet of barcodes. So RFID tags can be read much faster as compared to barcodes. While reading the barcodes is time consuming, RFID readers can interrogate rates of more than 40 tags in a second.

Need of line of sight in case of barcodes restricts reusability and ruggedness of the barcodes. RFID, on the other hand are rugged, since its components are protected in plastic cover. The Radio frequency Identification and Detection can also be fitted within the products for ensuring greater reusability and ruggedness. Unlike barcodes, RFID tags can be used as write and read devices. One can use RFID tags for communicating with the tag and for altering the information stored on it.

Current Scenario and future

Present trends point towards the fast growth of RFID in the next decade. With around 600 million RFID tags sold in the year 2005 alone, value of market including systems, services and hardware is likely to grow by factor of 10 between years 2006 -2016. It is expected that total number of RFID tags delivered in the year 2016 will be around 450 times as compared to the ones delivered in the year 2006.

Commercial applications using Radio Frequency Identification and Detection like logistics, transport, supply chain supervision, processing, manufacturing, medicine, access control are also likely to grow by leaps and bounds. But this smart technology will influence consumer sectors and government too. Barcodes and RFID will coexist for years to come, although the latter is expected to replace the former in many sectors.

Capacitors are charged with electricity, then releases its stored energy at a rate of sixty times per second in a 60 cycle alternating current system.The sizing is critical to motor efficiency just as sizing of batteries is critical to a radio. For example, a radio that requires a 9V battery will not work with a 1.5V size battery. Thus, as the battery becomes weaker the radio will not play properly.  A motor that requires a 7.5 mfd capacitor will not work with a 4.0 mfd capacitor. Much the same way, a motor will not run properly with a weak capacitor. This is not to imply bigger is better, because a capacitor that is too large can cause energy consumption to rise. In both instances, be it too large or too small, the life of the motor will be shortened due to overheated motor windings.

Motor manufacturers spend many hours testing motor and capacitor combinations to arrive at the most efficient combination. There is a maximum of +10% tolerance in microfarad rating on replacement start capacitors, but exact run capacitors must be replaced. Voltage rating must always be the same or greater than original capacitor whether it is a start or run capacitor. Always consult manufacturers to verify correct capacitor size for the particular application.

There are two basic types which are used in electric motor :

1. Run capacitorsare rated in a range of 3-70 microfarad (mfd).Run capacitorsare also rated by voltage classification. The voltage classifications are 370V and 440V. Capacitors with ratings above 70 microfarad (mfd) are starting capacitors.Run capacitorsare designed for continuous duty, and are energized the entire time the motor is running. Single phase electric motors need a capacitor to energize a second phase winding. This is why sizing is so critical. If the wrong run capacitor is installed, the motor will not have an even magnetic field. This will cause the rotor to hesitate at those spots that are uneven. This hesitation will cause the motor to become noisy, increase energy consumption, cause performance to drop, and cause the motor to overheat.

Themotor run capacitorsusually have two styles. one is metallized polypropylene AC / motor-run capacitors which are used in most of the older equipment. Large round metal cans. The other ismetallized polypropylene film capacitorsthat are much smaller and come with a mounting tab that can be screwed anywhere on the frame. of the unit. Both types offer the exact same qualities and electrical characteristics. Most important is to get the exact electrical ratings for the capacitor and then the case style.

2. Starting capacitors are housed in a black plastic case and have a mfd range as opposed to a specific mfd rating on run capacitors. Start capacitors (ratings of 70 microfared or higher) have three voltage classifications: 125V, 250V, and 330V. Examples would be a 35 mfd at 370V run capacitor and an 88-108 mfd at 250V start capacitor. Start capacitors increase motor starting torque and allow a motor to be cycled on and off rapidly. Start capacitors are designed for momentary use. Start capacitors stay energized long enough to rapidly bring the motor to 3/4 of full speed and are then taken out of the circuit.

Introduction of Motor

An electric motor is basically composed of windings around a magnet. Motors are either multi-phase or single-phase. Multi-phase motors generate starting torque along the various windings by applying out of phase voltages to each winding in a pattern that generates a torque force in the desired direction. Single-phase motors must generate the same starting torque however they have only one phase to work from. This means they have to have a method to generate a shifted version of the single phase voltage to send to one of their windings.

There are three common methods of creating single-phase electric motors: capacitor start, split-phase, and shaded pole. Each other these motors has some method to provide starting torque to the motor by shifting the voltage given to one of the windings on the motor by some angle. This phase shift corresponds to one winding of the motor having a voltage before another coil. The difference in time between when one coil has a voltage and when a second coil has a voltage causes the torque force and begins the movement of the motor.

To start to solve why capacitive start motors work we can generalize Ohm’s Law, V = IR, and say that V = IZ where Z is a generalized impedance. The impedance is composed of an the inductance, capacitance, and resistance. Inductance will cause the current to lag the voltage, capacitance will cause the current to lead the voltage, and resistance has no effect on the timing between the current and voltage.

The Function of The Start and Run Capacitor used for Motors

Most smaller, single phase motors usually have a permanent magnet armature that is pushed or pulled around by the rotating inductive field produced by the stator (outside) windings. The inductive field rotates simply as a result of the positive or negative alternations of the 60HZ AC current flowing through the windings. The problem is that when the voltage is applied, the 60HZ is applied immediately, the rotation of the field through the windings begins immediately, and the armature has no chance to react (or catch up, as it were) to the field.

The start Capacitor provides that electrical “push” to get the motor rotation started. It does this by creating a current to voltage lag in the seperate start windings of the motor. Since this current builds up slower, the armature has time to react to the rotating field as it builds up, and to begin rotating with the field. Once the motor is very close to it’s rated speed, a centrifugal switch disconnects the start cap and start windings from the circuit. Watching a single phase motor starting you can see that this all happens very quickly.

Without a start Capacitor(such as when one burns up) when the voltage is applied, the motor will just sit and hum. But if you were to grab the shaft and give it a spin, the motor would start and run normally.The run capacitor and aux. windings never drop out of the circuit in a cap-start, cap-run motor. The current to voltage lag is always present, which makes the motor act like a two phase motor. The advantage of a cap-start, cap-run motor over a cap-start, induction-run motor is that cap-run motors operate at a higher power factor than induction-run. Single cap-start / run motors use only one capacitor and are for lower torque applications.

Two value cap-start / run motors use two capacitors, a higer value capacitor for starting, and lower value for running. The centrifugal switch switches from the high capacitor to the low capacitor, but the aux windings never leave the circuit. Two-cap motors are for higher torque applications.

In a purely capacitive circuit the current will lead the voltage by 90 degrees. In a purely inductive circuit the current will lag the voltage by 90 degrees. Of course, there is always some resistance in any circuit, so whether inductive or capacitive, the lead / lag relationship between current and voltage will be somewhere between 0 and 90 degrees. I say all that to say this; the net effect of the difference in the capacitor is that it will change the angle of lead / lag between voltage and current in your motor.

In summary, the capacitor provides a delay in the energy given to one of the windings. This delay causes the forces of the motor to be unbalanced and the motor then starts. Economically, capacitor start motors are often more costly due to the inclusion of the capacitor however they have the most starting torque This means that you probably have one in your refrigerator, washer, dryer, or other application where you may need a lot of starting force but you won’t find them in your electric fan.

In addition,potential relays are also important. Potential relays are used to electronically connect and disconnect to starting capacitors from the motor circuit . Each relay has a specific voltage rating to place the start capacitor in series with the start winding and a specific voltage to take it out of the circuit. Each rating is based on the electromagnetic field generated by the rotation of the motor. The motor manufacturer studies the effect of placing in and taking out the capacitor to increase starting torque with as little winding flex as possible. Potential relays have four ratings:

• continuous coil voltage,
• minimum pick-up voltage,
• maximum pick-up voltage,
• drop out voltage.

A potential relay is difficult to check and should always be replaced when a start capacitor is replaced. The exact size designed for that particular motor must be reinstalled. The potential relay must also be replaced if contacts are found to be open.

The fundamental nature of these measurements makes them useful in a wide range of applications and disciplines. They are used in the research labs of universities and semiconductor manufacturers to evaluate new materials, processes, devices, and circuits. C-V measurements are extremely important to product and yield enhancement engineers, who are responsible for improving processes and device performance. Reliability engineers use these measurements to qualify material suppliers, monitor process parameters, and analyze failure mechanisms.

With appropriate methodologies, instrumentation, and software, a multitude of semiconductor device and material parameters can be derived. This information is used all along the production chain beginning with evaluation of epitaxially grown crystals, including parameters such as average doping concentration, doping profiles, and carrier lifetimes. In wafer processes, C-V measurements can reveal oxide thickness, oxide charges, mobile ions (contamination), and interface trap density. These measurements continue to be used after other process steps, such as lithography, etching, cleaning, dielectric and polysilicon depositions, and metallization. After devices are fully fabricated on the wafer, C-V is used to characterize threshold voltages and other parameters during reliability and basic device testing and to model the performance of these devices.

The Physics of Semiconductor Capacitance

A MOSCAP structure is a fundamental device formed during semiconductor fabrication. Although these devices may be used in actual circuits, they are typically integrated into fabrication processes as a test structure. Since they are simple structures and their fabrication is easy to control, they are a convenient way to evaluate the underlying processes.

The metal/polysilicon layer is one plate of the capacitor, and silicon dioxide is the insulator. Since the substrate below the insulating layer is a semiconducting material, it is not by itself the other plate of the capacitor. In effect, the majority charge carriers become the other plate. Physically, capacitance, C, is determined from the variables in the following equation:

C = A (?/d), where A is the area of the capacitor, ? is the dielectric constant of the insulator, and d is the separation of the two plates.

Therefore, the larger A and κ are, and the thinner the insulator is, the higher the capacitance will be. Typically, semiconductor capacitance values range from nanofarads to picofarads, or smaller.

The procedure for taking C-V measurements involves the application of DC bias voltages across the capacitor while making the measurements with an AC signal. Commonly, AC frequencies from about 10kHz to 10MHz are used for these measurements. The bias is applied as a DC voltage sweep that drives the MOSCAP structure from its accumulation region into the depletion region, and then into inversion

A strong DC bias causes majority carriers in the substrate to accumulate near the insulator interface. Since they can’t get through the insulating layer, capacitance is at a maximum in the accumulation region as the charges stack up near that interface (i.e., d is at a minimum). One of the fundamental parameters that can be derived from C-V accumulation measurements is the silicon dioxide thickness, tox.

As bias voltage is decreased, majority carriers get pushed away from the oxide interface and the depletion region forms. When the bias voltage is reversed, charge carriers move the greatest distance from the oxide layer, and capacitance is at a minimum (i.e., d is at a maximum). From this inversion region capacitance, the number of majority carriers can be derived. The same basic concepts apply to MOSFET transistors, even though their physical structure and doping is more complex.

Many other parameters can be derived from the three regions as the bias voltage is swept through them. Different AC signal frequencies can reveal additional details. Low frequencies reveal what are called quasistatic characteristics, whereas high frequency testing is more indicative of dynamic performance. Both types of C-V testing are often required.

Basic Test Setup

Because C-V measurements are actually made at AC frequencies, the capacitance for the device under test (DUT) is calculated with the following:

CDUT = IDUT / 2?fVAC, where IDUT is the magnitude of the AC current through the DUT, f is the test frequency, and VAC is the magnitude and phase angle of the measured AC voltage

In other words, the test measures the AC impedance of the DUT by applying an AC voltage and measuring the resulting AC current, AC voltage, and impedance phase angle between them. These measurements take into account series and parallel resistance associated with the capacitance, as well as the dissipation factor (leakage).

Challenges to Successful C-V Measurements

Certain challenges are associated with this testing. Typically, test personnel have problems in the following areas:

• Low capacitance measurements (picofarads and smaller values)
• C-V instrument connections (through a prober) to the • wafer device
• Leaky (high D) capacitance measurements
• Using hardware and software to acquire the data
• Parameter extractions

Overcoming these challenges requires careful attention to the techniques used along with appropriate hardware and software.

Low Capacitance Measurements. If C is small, the DUT’s AC response current is small and hard to measure. However, at higher frequencies, the DUT impedance is reduced, so the current increases and is easier to measure. Often semiconductor capacitance is very low (less than 1pF), which is below the capabilities of many LCR meters. Even those claiming to measure these small capacitance values may have confusing specifications that make it difficult to determine the final accuracy in the measurement. If accuracy over the instrument’s full measurement range is not explicitly stated, the user needs to clarify this with the manufacturer.

High D (Leaky) Capacitors. In addition to having a low C value, a semiconductor capacitor may also be leaky. That is the case when the equivalent R in parallel with C is too low. This results in resistive impedance overwhelming the capacitive impedance, and the C value gets lost in the noise. For devices with ultra-thin oxide layers, D values can be greater than five. In general, as D increases, the accuracy of a C measurement is rapidly degraded, so high D is a limiting factor in the practical use of a C meter. Again, higher frequencies can help solve the problem. At higher frequencies the capacitive impedance is lower, resulting in a C current that is higher and more easily measured.

C-V Measurement Connections. In most test environments, the DUT is a test structure on a wafer: It is connected to the C-V instrument through a prober, a probe card adapter, and a switch matrix. Even if no switch is involved, there is still a prober and significant cabling. At high frequencies, special corrections and compensation must be applied. Usually, this is achieved with some combination of an open, short, or calibration device. Because of the complexity of the hardware, cabling, and compensation techniques, it is a good idea to confer with C-V test application engineers. They are skilled at working with various probe systems to overcome many types of interconnection problems.

Obtaining Useful Data. In addition to the accuracy issues mentioned earlier, practical considerations in C-V data collection include the instrumentation’s range of test variables, versatility of parameter extraction software, and ease of hardware usage. Traditionally, C-V testing has been limited to about 30V and 10mA DC bias. However, many applications, such as characterizing LD MOS structures, low-kinterlayer dielectrics, MEMs devices, organic TFT displays, and photodiodes, require tests at higher voltage or current. For these applications, a separate high voltage DC power supply and C meter are required; DC bias up to 400V differential (0 to +/-400V) and a current output up to 300mA are very useful. Being able to apply differential DC bias on both the HI and LO terminals of the C-V instrument offers more flexible control over electric fields within the DUT, which is very helpful in the research and modeling of novel devices, such as nanoscale components.

The instrumentation software should include ready-to-run test routines that do not require user programming. These should be available for the most widely used device technologies and test regimens, which were mentioned in the first three paragraphs of this article. Some researchers may also be interested in less common tests, such as performing both a C V and C f sweep on a Metal Insulator Metal (MIM) capacitor, measuring small interconnect capacitance on a wafer, or doing a C V sweep on a two-terminal nanowire device. The parameter extractions should be easily obtained, with automated curve plotting.

Often, engineers and researchers are expected to perform C-V measurements with little experience and training on the instrumentation. A test system with an intuitive user interface and easy-to-use features makes this practical. That includes simple test setup, sequence control, and data analysis. Otherwise, the user spends more time learning the system than collecting and using the data. Other considerations are a test system with:

• Tightly integrated source-measure units, digital oscilloscope and C-V meter
• Easy integration with other external instruments
• High resolution and precise measurements at the probe tips (DC biasing down to millivolts and capacitance measurements down to femtofarads)
• Test setups and libraries that can be easily modified
• Diagnostic/troubleshooting tools that let users know whether or not the system is performing correctly.

In addition to the expense of purchasing and maintaining multiple test systems and training personnel to use them, the three-test system approach makes it difficult to combine different measurement types in a single application. When measurements are made at different times under varying test conditions with different instruments, accurately correlating results for a specific device or materials research sample becomes problematic.

A growing number of semiconductor devices and materials require testing with multiple measurement types. This makes it highly desirable to have a single test system with the capability to make all the measurements, controlled from a single easy-to-use operator interface.

Multiple-Measurement Applications. One test application requiring multiple measurements is charge pumping (CP), a well-known technique for analyzing the semiconductor/dielectric interface of MOS structures. Important information about the quality and degradation of a device can be extracted from charge pumping current (ICP) measurement results, including the interface trap density and the mean capture cross section. Pulsing a gate voltage and measuring a DC substrate current simultaneously is the basis for the various charge pumping methods, so both a pulse generator and sensitive DC ammeter are required to make these measurements.

Similarly, determining the electrical characteristics of photovoltaic (solar) cells often involves measuring the current and capacitance as a function of an applied DC voltage. The measurements are usually done at different light intensities and temperature conditions. Important device parameters can be extracted from the I-V and C-V measurements, such as the output current, conversion efficiency, maximum power output, doping density, resistivity, etc. Electrical characterization is also important to determine losses in the photovoltaic cell in order to learn how to make the cells as efficient as possible with minimal losses.

SMU-based Systems for DC I-V Testing. Early on, semiconductor test system manufacturers recognized the need for tightly integrated instrumentation capable of sensitive measurements, which could be operated in automatic, semi-automatic, and manual modes to accommodate a wide variety of test situations. These early semiconductor parameter analyzers concentrated on DC I-V measurements using multiple SMUs operated under computer control. An operator interface and system software simplified the process by providing ready-to run test routines for commonly used semiconductor tests.

These integrated parameter analyzers have been refined over time to provide more flexibility and sensitivity in DC I-V testing. For example, basic Model 4200-SCS Semiconductor Characterization System includes two medium-power SMUs. These SMUs can source voltage and current up to a 2W output (100mA max.) In addition, a high-power SMU option is also available (1A, 20W); the test system chassis can contain up to nine SMUs in any combination of high- and medium-powered units.

When stimulating a semiconductor device or material with a voltage, the response current can often be quite small, which a conventional SMU may not be able to measure accurately. To handle this situation, the Model 4200-SCS has a Remote PreAmp option that extends the low current measurement range down to 0.1fA (10-15A). In keeping with the desire for simplicity of use, the PreAmp module is fully integrated with the system. To the user, the SMU simply appears to have additional measurement ranges and resolutions available. The Remote PreAmp can also be placed remotely (such as in a light-tight enclosure or on a prober platen) to minimize measurement problems due to long cables.

A Breakthrough in C-V and Pulse Testing. A major advance in parameter analyzers occurred in 2007 when pulse I-V and C-V measurement capabilities were integrated with DC I-V in a single box test system, accomplished this by adding a plug-in module (Model 4210-CVU) to its Model 4200-SCS chassis for C-V testing. Pulse generator and oscilloscope modules also became available to facilitate pulse testing and response waveform analysis. The modular architecture of the system allows these capabilities to be added to existing units, or specified as options on new systems.

The optional CVU module makes C-V measurements as easy to perform as DC I-V testing. Capacitance from femtofarads (fF) to nanofarads (nF) at frequencies from 1kHz to 10MHz can be measured. This module supports high power C-V measurements up to 400V (200V per device terminal) for testing high power devices (MEMs, LDMOS devices, displays, etc.) and DC currents up to 300mA for measuring capacitance when a transistor is on.

These hardware capabilities are complemented by a broad C-V test and analysis library that becomes embedded in the operating system. This library allows configuring linear or custom C-V and C-f sweeps with up to 4096 data points.