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Various Digital Camcorders for Different Tastes and Needs

Monday, November 8th, 2010

Various Digital Camcorders for Different Tastes and Needs

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Home Page > Shopping > Various Digital Camcorders for Different Tastes and Needs

Various Digital Camcorders for Different Tastes and Needs

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Posted: Jan 06, 2010 |Comments: 0

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Various Digital Camcorders for Different Tastes and Needs
By: Tracy

About the Author
Felicia is from Chinazrh, which is an outstanding china wholesale electronics distributor with consumer electronics to meet you needs. Welcome to my blog: China wholesale electronics news to find more information you need and welcome your valuable suggestion. (ArticlesBase SC #1672543)
Article Source: http://www. articlesbase. com/ – Various Digital Camcorders for Different Tastes and Needs

A digital camcorder is a device that records images in a manner that is similar to that of a digital camera. A series of images is captured by collecting light from a subject and focusing it on a photosensitive substance inside the device. In an old movie camera, that substance was film. While with a digital camcorder, it is the light-sensitive imaging sensor (or multiple sensors) which converts the light into electric signals. The camcorder then internally converts those signals into video data, which it stores in one of a variety of media formats—mini DV tape, DVD disc, hard drive, or flash memory. Of course, audio is also captured and recorded simultaneously. We can witness that digital camcorders especial wholesale digital camcorders are enjoying increasing popularity. Indeed, digital camcorders make shooting video and editing it on your home computer a breeze. You can create movies and output them to tape or DVD, or post them on the Web. Whether you want to record shots of your new baby or you dream of becoming the next great film director, all you need is a good-performance digital camcorder. And it wise to choose one from a reliable and trustworthy online wholesale electronics store. But before you fall in love with just any old camcorder, you need to know precisely what you’re looking for, lest you realize somewhere down the road that you chose the wrong machine. Of course, you can read the customers’ review or ask for advice. But we all know that even a so-called digital camcorder is not suitable for everyone. What is more, it is a waste of time and money for an entry-level photographer to purchase a high performance digital camcorder. Ask yourself what you want to use it for before you make up your mind to choose the right digital camcorder from wholesale electronics suppliers. 1. For Home and vacation moviemaker If you just want to shoot birthday parties, baby steps, holiday gatherings and school plays and you plan to take you digital camcorder on vacations, a potable digital camcorder with simple controls and easy output is you ideal choice. You would like the option of doing a little editing and adding some basic effects. In this case, you need to spend several minutes to search and value some digital camcorders which supports 1080i or 720p high definition or standard definition video format and the lens type should be 10x or greater zoom controlled via switch or lens ring; electronic or optical image stabilization. Besides, the image sensor should be 1/6-inch or larger CCD, minimum 680,000-pixel effective video resolution for standard def; minimum 2-megapixel effective resolution for HD 2. For Budget buyer If your budget is the first factor you have to take into consideration and you cannot afford a digital camcorder which will cost you more than $4oo. Also, you don’t want a model that uses pricey cassettes or discs. Besides, you don’t need an advanced feature set or compatibility with lots of accessories don’t mind a relatively bulky design either. In this case, what is right for you is a basic camcorder that’s easy to use but that offers a design and features suited for more event-like shooting scenarios. With this in mind, your goal and requirement is much clearer. Choose one outstanding online wholesale electronics supplier and search the right digital camcorder with features suitable for your usage-standard definition video format, lens type of 10x or greater zoom controlled via switch, media of flash memory card. 3. For Independent filmmaker You are planning a documentary or a creative video want a camcorder that will give you the advanced controls for shooting. You also want excellent image quality and output in a format that is optimal for editing and applying effects. Yes, you can do without consumer-oriented bells and whistles, but you need compatibility with sound and lighting accessories because you to shoot like a pro. To best please you, a high-performance digital camcorder is a must. This digital camcorder whether you want to buy from a traditional walk-in store or wholesale electronics supplier online, it is better for you to take the following into consideration. The video format should be 1080i/p or 720p high definition or standard definition; Fixed lens with 10x or greater zoom or interchangeable lens system and zoom control via lens ring and switch as well as optical image stabilization; for the image sensor, three 1/6-inch or larger CCDs or CMOS chips (1/4- or 1/3-inch recommended) and minimum 345,000-pixel effective video resolution per sensor, minimum 1. 6 megapixels effective resolution per sensor for HD. Whether you are entry-level photographer or photography enthusiast or even professional cameraman, owing one digital camcorder for you matters much. We do wish the above can be a bit of help.

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Tracy -
About the Author:Felicia is from Chinazrh, which is an outstanding china wholesale electronics distributor with consumer electronics to meet you needs. Welcome to my blog: China wholesale electronics news to find more information you need and welcome your valuable suggestion.

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HTC T5388 With Many Different Features

Saturday, October 30th, 2010

HTC T5388 has a 3. 2 inches large touch screen, resolution of 480 × 800 pixels, crisp and clear display, allowing users to have a good visual. Also, the machine is built a 5 million pixel camera and supports auto focus, photo effects wise. Processors machine uses a 528MHz processor, runs smooth. Addition, this machine is equipped with Windows Mobile6. 1 operating system, all kind of good operability and scalability. The followed description is about HTC T5388 . Smart phone T5388 Unlocked Quad-band 3. 2? Touch Smartphone PDA T5388 +2GB Built-in GPS navigation chip, dual-camera, with auto focus function, CMOS sensor GPS Windows Mobile 6. 1 Professional, JAVA, Wi-Fi CPU: Marvell Pxa310 1G MHz Rom 256MB+ Ram 192MB The T5388 Smartphone PDA supports quadband frequency of GSM 850 / 900 / 1800 / 1900 MHz. The phone can be used worldwide. Camera: 5 million pixels Screen Color: 65536 thousand colors language: English only(ONLY can install one language) Colour Available :Black Application included: Word, Excel, Powerpoint, OneNote, Outlook, Acrobat Reader, Interent Explorer, Windows Media Player and more. You can download and install additional application from internet. Function: 1. Data applications Bluetooth: Supports Bluetooth, EDR, A2DP Bluetooth stereo Data services: GPRS, EDGE JAVA: Java MIDP 2. 0, CLDC1. 1 Wifi (WLAN): Support Wifi, support for 802. 11b / g GPS Positioning System: Support for GPS, built-in GPS navigation chip, support A-GPS, network-assisted navigation features, but buyers need to download maps. 2. Camera Camera pixels: 500 million pixels, auto focus, CMOS sensors; Vice Camera: Built-in 1. 3 million pixel deputy camera, ; Shooting mode: support for white balance adjustment, exposure compensation adjustment support; Photo Quality: Support maximum resolution of 2592 * 1944 photo shoot; Video recording: audio video recording. 3. Multi-media entertainment functions Multimedia: Support FM radio; MP3 Player: Support MP3 player, built-in WINDOWS MediaPlayer, support multiple audio format player (supports background play, Playlist Editor, EQ sound adjustment and Loop settings); Other features: the focus of force sensing, using HTC TouchFLO technology, corresponding to a finger touch operation. From above,you can have a general knowledge of HTC T5388. You can pay attention to HTC T5388 that shares some similarities with HTC 5388,maybe you will like it. But you also buy Replica HTC with high quality and reasonable price. Joanne-myreplicaphone Article from: www. myreplicaphone. com

Tags: Different, features, Many, T5388
Posted in CMOS Ram | No Comments »

Operational review of different mechanisms of control stepper motor

Sunday, August 1st, 2010

This section covers all types of engines, from basic circuits needed to control a variable reluctance motor, the H-bridge circuit to control a permanent magnet motor pole. Each type of control circuit is illustrated with practical examples, but these examples are not intended as an exhaustive catalog of the control circuits commercially available, or the information contained herein is intended to replace the information found on the leaves manufacturer’s data components for the parties mentioned. This section covers only the control circuit of the most basic class for each engine. All these circuits assume that the power of the engine provides a control voltage does not exceed the rated motor voltage, which limits the performance of the engine. The next section, the control circuit current limited, practical circuits covers high performance training. controllers of variable reluctance motors typical reluctance stepper motors are variable variations on the contour of Figure 3. 3 Figure 1:. 1 In Figure 3. 1, boxes are used to represent the switches, a control unit, not shown, is responsible for providing control signals to open and close the switches at the right time to turn the motors. In many cases, the unit will control a computer or programmable interface controller, the software directly generating the outputs needed to control the switches, but in other cases, an additional control circuit is introduced, sometimes free! motor windings, solenoids and similar devices are all inductive loads. As such, the current through the motor windings can be switched on or off instantly without going through endless tension! When the switch controlling a motor winding is closed, allowing current to flow, the result of this is a slow rise in current. When the switch control of a motor winding is opened, the result is a voltage spike that can cause serious damage to the switch unless care is taken to appropriate care. There are two basic ways to cope with the peak voltage. The first is to bridge the motor winding with a diode, and the other is to bridge the motor winding with a capacitor. Figure 3. Figure 2 illustrates the two approaches: Figure 3. 2 The diode in Figure 3. 2 must be able to conduct electricity across the motor winding, but it did lead briefly each time the switch is off, as the current through the decays of liquidation. If diodes relatively slow, as the common family 1N400X are used with a switch quickly, it may be necessary to add a small capacitor in parallel with the diode. The capacitor in Figure 3. Poses two problems more complex design! When the switch is closed, the capacitor discharges through the ground, and the switch must be able to manage this short burst of discharge current. A resistor in series with the capacitor or in series with the power supply will limit the current. When the switch is opened, the stored energy in the motor winding will charge the capacitor to a voltage much higher than the supply voltage, and the switch must be able to tolerate this tension. To solve for the size of the capacitor, we equate the two formulas for the energy stored in a resonant circuit: P = C V2 / 2 P = I2 L / 2 where: P – stored energy in seconds or watt coulomb volt C – the capacity in farads V – voltage across capacitor L – inductance of the motor winding, in henrys I – current through the motor winding resolution for the minimum size of capacitor needed to prevent surges on the switch is easy enough: C> L I2 / (Vb – Vs) 2 Where: Vb – the breakdown voltage Vs of the switch – the power supply of variable reluctance motors have variable inductance which depends on the angle tree. Therefore, the design of the worst must be used to select the capacitor. In addition, the motor inductances are often poorly documented, if at all. The capacitor and the motor winding, in combination, form a resonant circuit. If the control system drives the motor at frequencies near the resonant frequency of this circuit, the motor current in the windings and, therefore, the torque exerted by the engine torque will be very different from the state equilibrium the nominal operating voltage! The resonant frequency is f = 1 / (2 (SC) 0. 5) Again, the frequency of electrical resonance for a variable reluctance motor depends on the angle tree! When a variable reluctance motor is used with interesting impulses near the resonance, the oscillating current in the motor winding leads to a magnetic field which tends to zero at twice the resonant frequency, which can significantly reduce the torque available! controllers unipolar permanent magnet and hybrid motors typical unipolar stepper motors are variations on the outline of Figure 3. 3: Figure 3. 3 in Figure 3. 3, as in Figure 3. 1, boxes are used to represent the switches, a control unit, not shown, is responsible for providing control signals to open and close the switches at the right time to turn the motors. The control unit is typically a computer or programmable interface controller, with the software directly generating the outputs needed to control the switches. As control circuit for variable reluctance motors, we must deal with the sudden inductive produced when each of these switches is turned off. Again, you can blow the inductive shunt using diodes, but now, four diodes are required, as shown in Figure 3. 4: Figure 3. The four diodes are needed because the motor’s two coils are not independent, there is a single center-tapped inductor with center tap at a fixed voltage. This acts as an auto! When one end of the motor winding is pulled down, the other end of fly, and vice versa. When a switch opens, the inductive kickback drive end of the motor winding to the positive supply, where it is clamped by the diode. The opposite end will fly down, and if it does not float to the voltage at the time, it will fall below the ground, reversing the voltage across the switch for this purpose. Some switches are immune to such reversals, but others may be seriously damaged. A capacitor can also be used to limit the voltage bounce, as shown in Figure 3. 5: Figure 3. 5 The rules for sizing the capacitor in Figure 3. 5 are the same as the rules for the dimensioning of the capacitor in Figure 3. 2, but the resonance effect is very different! With a permanent magnet motor, if the capacitor is driven at or near the resonant frequency, the couple will rise to as much as twice the torque at low speed! The resulting torque versus speed curve may be quite complex, as illustrated in Figure 3. 6: Figure 3. 6 Figure 3. Figure 6 shows a peak in the available torque to the frequency of electrical resonance, and a valley at the mechanical resonance frequency. If the frequency of electrical resonance is placed appropriately above what would be the threshold speed of the engine using a diode pilot basis, the effect may be a considerable increase of the effective cut-off speed. The mechanical resonance frequency depends on the couple, if the mechanical resonance frequency is anywhere near the electrical resonance, it will be moved by the electric resonance! In addition, the width of the mechanical resonance depends on local slope of torque versus speed curve, if the torque with speed, mechanical resonance will be crisp, while if the torque increases to a speed, will be broader or even split into several resonant frequencies. Practices unipolar and variable reluctance Drivers In circuits above, the details of necessary switches have been deliberately ignored. All the technology switching, toggle switches power MOSFET will work! Figure 3. 7 contains some suggestions for the implementation of each switch, with a motor winding and diode protection included for guidance: Figure 3. 7 Each of the switches in Figure 3. 7 is compatible with a TTL input. The 5-volt supply used for logic, including the 7407 open collector driver used in the figure should be well regulated. The engine power, typically between 5 and 24 volts, needs only minimal regulation. It should be noted that these power switching circuits are suitable for driving solenoids, DC motors and other inductive loads, and for driving stepper motors. Transistor SK3180 shown in Figure 3. 7 is a darlington power with a current gain over 1000, and the 10 milliamps passing through the resistance of 470 ohm bias is more than sufficient to allow the transistor to switch a few amps current in the windings. The buffer used to drive the 7407 Darlington can be replaced by a smart open-collector high voltage that can run at least 10 milliamperes. If the transistor fails, the driver high voltage open collector is used to protect the rest of the logic circuit of the motor. The IRC IRL540 shown in Figure 3. 7 is a transistor electric field effect. It can handle currents up to about 20 amps, and it goes down to 100 volts non-destructive, so the chip can absorb inductive spikes without protection diodes if it is attached to a heat sink big enough. This transistor has a very fast switching time, then protection diodes must be comparable or faster bypassed by small capacitors. This is especially important with the diodes used to protect the transistor against reverse bias! If the transistor fails, the zener diode and 100 ohm resistor protect TTL circuits. The resistance of 100 ohms also acts to slightly slow down the switching transistor. For applications in which each motor winding draws less than 500 milliamps, the family of tables ULN200x Darlington Allegro MicroSystems, also available as DS200x National Semiconductor and Motorola MC1413 Table Darlington lead several motor windings or other charges directly from inductive logic inputs. Figure 3. Figure 8 shows the pinout of the chip ULN2003 widely available, a Darlington transistor array 7 with TTL compatible inputs: Figure 3. 8 The base resistance on each Darlington transistor corresponds to the standard bipolar TTL outputs. NPN Darlington Each is wired with its emitter connected to pin 8, designed as a grounding prong, each transistor in the package is protected by two diodes, a short-circuit the emitter to the collector, protection against reverse polarity to through the transistor, and connecting the collector to pin 9, if pin 9 is connected to the motor power supply positive, the diode to protect the transistor against inductive spikes. The ULN2803 chip is essentially the same as the ULN2003 chip described above, except that it is in a 18-pin package, and contains 8 Darlingtons, allowing a chip to be used to drive a pair of common unipolar permanent magnet or variable reluctance motors. For motors drawing less than 600 milliamps per winding, the pilot quad UDN2547B authority made by Allegro Microsystems will manage all four windings of stepper motors unipolar common. For motors drawing less than 300 milliamps per winding, Texas Instruments SN7541, 7542 and 7543 dual power drivers are a good choice, both options include some logic to the pilot power. Motors bipolar H-Bridges and activities are more complex permanent magnet bipolar stepper motors because they have no center taps of their windings. Therefore, to reverse the direction of the field produced by a motor winding, we need to reverse the current in the coil. We could use a solid double pole switch electromechanical To do this, the electronic equivalent of such a change is called an H-bridge and is described in Figure 3. 9 As with unipolar control circuits mentioned above, the switches used in the H-bridge must be protected against voltage spikes caused by switching off a motor winding. This is usually done with diodes, as shown in Figure 3. 9. It should be noted that H-bridges are not only the control of bipolar stepper motors, but also for the control of DC motors, solenoids, push-pull (those divers with permanent magnet) and many other applications. With 4 switches, the basic H-bridge has 16 possible operating modes, including seven short-circuiting the power! The following operating modes are interesting mode of delivery, switches A and D closed. Reverse mode, switch B and C are closed. These are the usual modes of operation, allowing current to flow from the supply through the motor windings and beyond the earth. Figure 3. 10 illustrates the preliminary mode: Figure 3. 10 decay mode or fast mode freewheeling, open all switches. Any current flowing in the motor windings will work against the full supply voltage plus two diode drops, so current decay rapidly. This mode provides dynamic braking effect is little or no motor rotor, so that the rotor side freely if all motor windings are energized in this mode. Figure 3. 11 illustrates the current flow immediately after the passage of the attacker runs a fast decay mode. Figure 3. 11 modes decay slowly or dynamic braking mode. In these modes, the current can flow through the motor winding with minimal resistance. Therefore, if current flows in a coil of the motor when one of these modes is entered, the current will slowly decay, and if the motor rotor rotates, it induces a current which will act as a brake on the rotor . Figure 3. 12 illustrates one of many useful slow decay modes, D with the switch closed if the motor winding has recently been in fashion forward, the state of the switch B may be open or closed: Figure 3. Most of the 12 H-bridges are designed so that the logic necessary to avoid a short circuit is included at a very low level in the design. Figure 3. 13 illustrates what is probably the best arrangement: Figure 3. 13 Here, the following operating modes are available: XY decay mode ABCD 00 0000 1001 01 Fast forward 10 11 0101 0110 Reverse slow decay The advantage of this arrangement is that all the relevant modes are retained, and they are encoded with a minimum number of bits, it is important when using a microcontroller or a computer system to drive the H-bridge because many of these systems have limited the number of bits available for parallel output. Sadly, few chip H-bridge integrated on the market of such a system of simplified control. Practice Bipolar Drive Circuits There are a number of H-bridge driver integrated market, but it is always useful to consider the implementations of discrete components to understand how an H-bridge Antonio Raposo (RDA @ Cybill. INESC. Pt) suggested the H-bridge circuit in Figure 3. 14; Figure 3. 14 The X and Y to the inputs of this circuit can be driven by open collector TTL outputs as in the control circuit unipolar Darlington basis of Figure 3. 7. The motor winding will be energized if exactly one of X and Y inputs is high and one of them is low. If both are low, both transistors will drop off. If both are high, both transistors of pull-up will be off. Consequently, this simple circuit is the engine braking mode dynamics in both the 11 and 00 states, and does not offer a freewheeling mode. The circuit in Figure 3. 14 consists of two identical halves, each of which can be properly described as a push-pull driver. The half life of H-bridge is sometimes applied to these circuits! It is also interesting to note that half H-bridge circuit is quite similar to the output control circuit used in TTL logic. In fact, the TTL line driver tri-state actors such as the 74LS244 74LS125A and can be used as a half-H bridge for small loads, as shown in Figure 3. 15: Figure 3. 15 This circuit is effective for driving motors with a maximum at about 50 ohms per winding voltages up to about 4. 5 volts with a supply of 5 volts. Each buffer three states in the LS244 can run about twice today and you can source and internal resistance of buffer is sufficient, when the supply current to be divided equally between the current drivers that are executed in parallel. This device allows all relevant States obtained by the driver in Figure 3. 13, but these states are not coded as efficiently: XYE Fashion – 1000 fast decay slow disintegration advance 100,010,110 reverse slow decay The second dynamic braking mode, XYE = 110, gives a slightly lower than the first braking due to the fact that the LS244 drivers can fall more power than they can source. The microprocessor (formerly Telcom Semiconductor) TC4467 Quad CMOS driver is another example of a general purpose driver that can be used as four independent H Half-bridges. Unlike the old drivers, the data sheet for this driver even suggested using it for motor control applications with supply voltages up to 18 volts and 250 milliamps per winding engine. One problem with the intensification of chips available on the market of motor control is that many of them have relatively short life of the contract. For example, Seagate Series IPxMxx chip dual H-bridge (by IP1M10 IP3M12) were very well thought out, but unfortunately it appears that Seagate does this when they used stepper motors for positioning in the minds of readers Seagate disk. The Toshiba TA7279 dual H-bridge would be another choice of another great engines of less than 1 amp, but again he seems to have been made for internal use. SGS-Thompson (and others) L293 dual H-bridge is a direct competitor for the chips above, but unlike them it does not include protection diodes. The L293D chip, introduced later, is pin-compatible and includes these diodes. If the previous L293 is used, each motor winding must be resolved through a bridge rectifier (1N4001 equivalent). The use of LEDs allows a series resistor to be placed in the recirculation current to accelerate the decomposition of the current in a motor winding when turned off, which may be desirable in certain applications. The family L293 offers an excellent choice for driving small bipolar stepper development of one ampere per motor winding up to 36 volts. Figure 3. 16 shows the pinout common L293B L293D and chips: Figure 3. 16 This chip can be considered independent 4-H Half bridges, has allowed two or two-H bridges complete. This is a power DIP package with pins 4, 5, 12 and 13 for conducting heat from the PC card or an external heat sink. SGS-Thompson (and others) L298 dual H-bridge is quite similar to the above, but is able to handle up to 2-A per channel and is packaged as a component of power, as with the LS244, the is sure the two bridges over M-298 Packaged in a 4-Amp H-bridge (the data sheet for this chip provides specific advice on how to do). A warning is appropriate for the 298, the chip switches very fast, fast enough that the current protection diodes (equivalent 1N400X) does not work. Instead, use a diode as the BYV27. The National Semiconductor LMD18200 H-bridge is another good example, which can handle up to 3 amps and has full protection diodes. Although integrated H-bridges are not available for very high currents or very high voltages, there are many on the market designed components to simplify construction of bridges from H-discrete switches. For example, International Rectifier sells a line of half H-bridge drivers, two of these chips over four MOSFET switching transistor is sufficient to construct an H-bridge The IR2101, IR2102 IR2103 and are based half H-bridge drivers. Each chip has two digital inputs to directly control the two switching transistors on a leg of an H-bridge The IR2104 and IR2111 same logic side output switches to control a H-bridge, but they also understand the logic input side, in some applications, may reduce the need for external logic. In particular, the 2104 includes an enable input, while in April 2104 more chips switching transistor 8 can replace L293 without requiring additional logic. The data sheet of the chip (formerly Telcom Semiconductor) TC4467 Quad CMOS family of drivers includes information on how to use the drivers of this family to lead the Power MOSFET H-bridges running up 15 volts. A number of chip makers are complex H-bridge circuits that include current limit, it is the subject of the next section. It is also interesting to note that there are a number of 3-phase bridge drivers on the market, suitable for driving the Y or triangle configured three-phase permanent magnet steppers. Few of these engines are available, and these chips have been developed with steppers in mind. However, the Toshiba TA7288P, the GL7438, the TA8400 and TA8405 are own creations, and two such chips, with one of six half-bridges ignored, will properly monitor a 5-winding 10 steps per motor revolution.

Tags: Control, Different, Mechanisms, Motor, Operational, Review, stepper
Posted in CMOS Buffer | 1 Comment »

Operating Analysis of Different Stepping Motor Control Mechanisms

Thursday, April 15th, 2010

This section covers all types of engines, ranging from basic circuits needed to control a variable reluctance motor, the H-bridge circuitry needed to control a motor pole permanent magnet. Each class drive circuit is illustrated by practical examples, but these examples are not intended to be an exhaustive catalog of the control circuits commercially available, or the information contained herein intended to substitute for information found on the manufacturer data sheets for components parts mentioned. This section covers only the most elementary circuits of control for each engine category. All these circuits assume that the power of the engine provides a control voltage does not exceed the rated motor voltage, which substantially limits the performance of the engine. The next section, the circuit current limited disk covers circuits practice high-performance disk. Variable reluctance controllers typical reluctance stepper motors variable are variations on the contour of Figure 3. 1: Figure 3. 1 in Figure 3. 1, the boxes are used to represent the switches, a control unit, not shown, is responsible for providing control signals to open and close the switches at the appropriate times to run the engines. In many cases, the control unit is a computer or programmable interface controller, with software directly generating the outputs needed to control the switches, but in other cases, an additional control circuit is introduced, sometimes free ! The windings of motors, solenoids and similar devices are all inductive loads. As such, the current in the motor winding can be switched on or off instantly without involving infinite tension! When the command switch of a motor winding is closed, allowing current to flow, the result of this is a slow rise in current. When the command switch of a motor winding is opened, the result of this is a point of tension that can seriously damage the switch unless care is taken to address them appropriately. There are two basic ways to cope with the peak voltage. One is to bridge the motor winding with a diode, and the other is to bridge the motor winding with a capacitor. Figure 3. 2 illustrates two approaches: Figure 3. 2 The diode in Figure 3. 2 must be capable of full flow through the motor winding, but it did lead briefly when the switch is off, as the current through the winding declines. If diodes relatively slow, as the common family 1N400X are used in conjunction with a quick switch, it may be necessary to add a small capacitor in parallel with the diode. The capacitor in Figure 3. 2 presents design problems more complex! When the switch is closed, the capacitor discharges through the switch to ground, and the switch must be able to handle the brief surge of discharge current. A resistor in series with the capacitor or in series with the power will limit the current. When the switch is open, energy stored in the motor winding to charge the capacitor to a voltage well above the supply voltage and the switch must be able to withstand this tension. To solve for the size of the capacitor, we equate the two formulas for the energy stored in a resonant circuit: P = C V2 / 2 R P = I2 / 2 Where: P – stored energy in seconds or watt coulomb volt C – capacity in farads V – voltage across capacitor L – inductance of the winding engine, Henry I – current in motor winding Solving the minimum size of capacitor required to avoid overvoltage on the switch is easy enough: C> L I2 / (Vb – Vs) 2 where: Vb – the breakdown voltage of the VS switch – the voltage variable reluctance inductor have a variable that depends on the angle of the shaft. Therefore, the worst case, the design must be used to select the capacitor. In addition, the motor inductances are often poorly documented, if at all. The capacitor and the motor winding, in combination, form a resonant circuit. If the control system drives the motor at frequencies near the resonant frequency of this circuit, the motor current through the motor windings and, therefore, the torque exerted by the engine will be very different from the torque of the steady state at nominal operating voltage! The resonant frequency is: F = 1 / (2 (SC) 0. 5) Again, the resonance frequency for an electric motor with variable reluctance depends on the angle of a tree! When a variable reluctance motor is used with pulse exciting near resonance, the oscillating current in the motor winding leads to a magnetic field that goes from zero to twice the resonance frequency, which can seriously reduce the Couple available! Controllers unipolar permanent magnet motors and the typical hybrid stepper motors unipolar are variations on the contour of Figure 3. 3: Figure 3. 3 in Figure 3. 3, as shown in Figure 3. 1, the boxes are used to represent the switches, a control unit, not shown, is responsible for providing control signals to open and close the switches at the appropriate times to run the engines. The control unit is typically a computer or programmable interface controller, with software directly generating the outputs needed to control the switches. As for the control circuits for variable reluctance motors, we must deal with the inductive stroke occurs when each of these switches is turned off. Again, we may shunt the kick induction using diodes, but now, 4 diodes are required, as shown in Figure 3. 4: Figure 3. 4 The diodes are needed because the motor winding is not two independent inductors, it is a single center operated inductor with center tap at a fixed voltage. This acts as an autotransformer! When one end of the motor winding is pulled down, the other end will fly up, and vice versa. When a switch opens, the inductive bounce will drive this end of the motor winding to the positive supply, where it is blocked by the diode. The opposite end will fly down, and if it was not floating at the voltage at the time, it will fall under the ground, reversing the voltage across the switch to this end. Some switches are immune to such turnarounds, but others may be seriously damaged. A capacitor may also be used to limit the voltage bounce, as shown in Figure 3. 5: Figure 3. 5 The rules for sizing the capacitor in Figure 3. 5 are the same as the rules for sizing the capacitor in Figure 3. 2, but the resonance effect is quite different! With a permanent magnet motor, if the capacitor is driven at or near the resonant frequency, the couple will rise to as much as twice the torque at low speed! The resulting torque curve over-speed may be quite complex, as illustrated in Figure 3. 6: Figure 3. 6 Figure 3. Figure 6 shows a peak in the available torque to the electric resonance frequency, and a valley at the mechanical resonance frequency. If the frequency of electrical resonance is placed appropriately above what would have been cut-off speed of the engine using a diode-PF, the effect may be a considerable increase in the rate cut effective. The mechanical resonance frequency depends on the couple, so if the frequency of mechanical resonance is nowhere near the electric resonance, it will be moved by the electric resonance! In addition, the width of the mechanical resonance depends on the local slope of torque versus speed curve, if the torque decreases with speed, mechanical resonance will be sharper, while if the couple climbs at a speed, it will be broader or even split into several resonant frequencies. Practice Unipolar and Variable Reluctance Drivers In the circuit above, the details of necessary switches have been deliberately ignored. Any technology switching, toggle switches to operate power MOSFET! Figure 3. 7 contains some suggestions for implementation of each switch, a motor winding and a diode protection included for guidance: Figure 3. 7 Each of the switches in Figure 3. 7 is compatible with a TTL input. The 5 volt power supply used for logic, including the 7407 driver is open-sensors used in the figure must be well regulated. The engine power, typically between 5 and 24 volts, needs only minimal regulation. Note that these circuits are switching power supply suitable for driving solenoids, DC motors and other inductive loads and for driving stepper motors. SK3180 transistor shown in Figure 3. 7 is a Darlington power with a current gain over 1000: thus, the 10 milliamps passing through resistance of 470 ohms is more than sufficient to allow the transistor to switch a few amperes of current in motor winding. The stamp of 7407 used to drive the Darlington May be replaced by a chip high voltage open collector can sink at least 10 milliamperes. In the case where the transistor fails, the pilot high voltage open collector is used to protect the rest of the logic circuits from the power of the engine. The IRC IRL540 shown in Figure 3. 7 is a transistor having a force field. It can handle currents up to about 20 amps, and it decomposes nondestructive 100 volts, therefore, this chip can absorb inductive spikes without diode protection if it is attached to a large enough heat sink. This transistor has a switching time very fast, so the protection diodes must be comparable or faster bypassed by small capacitors. This is especially important with the diodes used to protect the transistor bias against cons! In the case where the transistor fails, the Zener diode and 100 ohm resistor protect TTL circuits. The resistance of 100 ohms also acts to slow a little time on the switching transistor. For applications in which each motor winding draws less than 500 milliamps, the family ULN200x tables Darlington Allegro Microsystems, also available as DS200x from National Semiconductor, and as the Motorola MC1413 table Darlington will drive the motor windings or multiple of other inductive loads directly from the inputs. Figure 3. Figure 8 shows the pinout of the chip ULN2003 widely available, a table of 7 Darlington transistors with TTL compatible inputs: Figure 3. 8 The basic resistance of each transistor Darlington corresponds to standard bipolar TTL outputs. Each darlington NPN is wired with its emitter connected to pin 8, designed as a grounding prong, each transistor in the package is protected by two diodes, short-circuiting the emitter and collector, protection against reverse voltages through the transistor, and one connecting the collector to the pin 9, and if the pin 9 is connected to the positive power of the engine, this diode will protect the transistor against inductive spikes. ULN2803 chip is essentially the same as the ULN2003 chip described above, except that a 18-pin package, and contains 8 DARLINGTONS, allowing one chip to be used to drive a pair of common magnet pole permanent and variable reluctance motors. For motors drawing less than 600 milliamps per winding, power quad UDN2547B pilot made by Allegro Microsystems will take care of all 4 common windings of stepper motors unipolar. For motors drawing less than 300 milliamps per winding, Texas Instruments SN7541, 7542 and 7543 drivers double power, are a good choice, both options include some logic with the pilot power. Motors and bipolar H-Bridges things are more complex permanent magnet bipolar stepper motors because they have no center taps on their windings. Therefore, to reverse the direction of the field produced by a motor winding, we need to reverse the current in the coil. We could use a double-pole double-throw electromechanical switch to do the electronic equivalent of such a change is called an H-bridge and is described in Figure 3. 9 As with the unipolar drive circuits discussed above, the switches used in the H-bridge must be protected against voltage spikes caused by off in a motor winding. This is usually done with diodes as shown in Figure 3. 9. It is noteworthy that H-bridges are applicable not only to control stepper motors bipolar, but also for control of DC motors, push-pull solenoids (those divers with permanent magnets) and many other applications. With 4 switches, the H-bridge has 16 basic modes of operation possible, including 7 short-circuiting the power! The following operating modes are of interest: forward mode, switches A and D closed. Reverse mode, the switch B and C closed. These are the usual modes of operation, allowing current to flow of food through the motor winding and beyond the earth. Figure 3. 10 shows forward mode: Figure 3. 10 fast decay mode or freewheel mode, all switches open. Any current flowing in the motor winding will work against voltage track, plus two drops of diode current to decay rapidly. This method offers little or no effect dynamic braking of the motor rotor, so that the rotor side freely if all motor windings are powered in this mode. Figure 3. 11 illustrates the flow of current immediately after switching from forward mode to perform a rapid decline. Figure 3. 11 ways to slow decay modes or dynamic braking. In these modes, during May to circulate through the motor winding with minimal resistance. Consequently, if the current flows in a winding engine when one of these modes is entered, the current decay slowly, and if the motor rotor turns, it will induce a current which will act as a brake on the rotor . Figure 3. 12 illustrates one of many useful slow decay modes, D with switch closed and if the motor winding has recently been running mode ahead, the state of the switch B may be open or closed: Figure 3. H-12 Most bridges are designed so that the logic necessary to prevent a short circuit is at a very low level in the design. Figure 3. 13 illustrates what is probably the best arrangement: Figure 3. 13 Here, the following operating modes are available: XY ABCD 00 0000 rapidly decreasing 01 1001 before 10 0110 Reverse 11 0101 slow decay The advantage of this arrangement is that all relevant modes are preserved and that they are encoded with a minimum number of bits, it is important when using a microcontroller or a computer system to drive the H-bridge because many numbers of these systems have little bits available for the parallel output. Unfortunately, few integrated H bridge chips on the market have such a simple control system. Practice Bipolar Circuits There are a number of H-bridge driver integrated market, but it is always useful to examine the implementations of discrete components to understand how an H-Bridge Works. Antonio Raposo (RDA @ Cybill. INESC. Pt) proposed the H-bridge circuit of Figure 3. 14; Figure 3. 14 inputs X and Y for this circuit can be powered by open-collector TTL outputs as in the unipolar DARLINGTON-based drive circuit in Figure 3. 7. The motor winding will be supplied if exactly one of the inputs X and Y is high and precisely one of them is low. If both are low, both pull-down transistors are off. If both are high, both pull-up transistors are off. Consequently, this simple circuit is the engine braking mode dynamics in both the 11 and 00 states, and does not offer a way of cabotage. The circuit of Figure 3. 14 consists of two identical halves, each of which may be properly described as a push-pull driver. Half Term The H-bridge is sometimes applied to these circuits! It is also interesting to note that a half H-bridge circuit is quite similar to the output circuit drives used in TTL logic. In fact, TTL tri-state line drivers such as the 74LS244 and 74LS125A can be used as a half H-bridges for small loads, as shown in Figure 3. 15: Figure 3. 15 This circuit is effective for driving motors with a maximum of about 50 ohms per winding tension less than about 4. 5 volts with a supply of 5 volts. Each tri-state buffer in the LS244 can run about twice the current it can source and internal resistance of the buffer is sufficient, which take their course, to share power equitably among drivers who are executed in parallel. This drive motor for all relevant states obtained by the driver in Figure 3. 13, but these states are not coded as efficiently: XYE Mode – 1 rapid disintegration disintegration 000 slow 010 forward 100 reverse 110 The second slow decay mode DB, XYE = 110, provides a marginally weaker than the first braking due to the fact that the LS244 drivers may fall more power than they can source. The microprocessor (formerly Telcom Semiconductor) TC4467 Quad CMOS driver is another example of a general purpose driver that can be used as 4 semi-independent H-bridges. Unlike the old drivers, the data sheet for this driver even suggests the use of applications for motor control, with supply voltages of 18 volts and 250 milliamps per winding engine. One problem with the chips on the market for controlling stepper motors is that many of them have lifetimes market relatively short. For example, the Seagate IPxMxx series of H-bridge chips double (IP1M10 by IP3M12) was very well thought out, but unfortunately it seems that Seagate made these when they used stepper motors to position the head in Seagate. The Toshiba TA7279 dual H-bridge driver is another excellent choice for engines with another of less than 1 amp, but again, it seems to have been made for internal use. The SGS-Thompson (and others) L293 dual H-Bridge is a direct competitor for bullets above, but unlike them it does not include protection diodes. The L293D chip, introduced later, is pin-compatible and includes these diodes. If the earlier L293 is used, each motor winding must be resolved through a bridge rectifier (1N4001 equivalent). Using external diodes allows a series resistor to be placed in the path of recirculation current to accelerate the decomposition of the current in a coil when the engine is off, this may be desirable in certain applications. The family L293 offers an excellent choice for driving small bipolar stepper development of one ampere by the motor winding up to 36 volts. Figure 3. 16 shows the pinout common chip L293D and L293B: Figure 3. 16 This chip may be regarded as semi-independent 4-H bridges, has allowed two or as two full H bridge. This is a SMD power package with 4 pins, 5, 12 and 13 to conduct heat to the circuit board or an external heat sink. The SGS-Thompson (and others) L298 dual H-bridge is quite similar to the above, but which is capable of handling up to 2 amps per channel and is packaged as a component of power, as with the LS244, it is security of the H son of two bridges in the package 298 in one of the 4-H-AGP bridge (the data sheet for this chip provides specific advice on how to do). A warning is appropriate on the 298, the switches of this chip very fast, fast enough that the current protection diodes (equivalent 1N400X) does not work. Instead, use a diode as the BYV27. The National Semiconductor LMD18200 H-bridge is another good example, which manages up to 3 amps and has full protection diodes. While H built bridges are not available for very high currents or very high voltages, it is well designed components on the market to simplify the construction of bridges in H from separate switches. For example, International Rectifier sells a range of half H-bridge drivers, two of these chips over 4 MOSFET switching just build a bridge H. The IR2101, IR2102 and IR2103 are based H half bridge drivers. Each chip has 2 inputs to directly control the two switching transistors on a leg of a H-bridge The IR2104 and IR2111 have the same logic output side to control the switches of an H-bridge, but they also understand the logic input side, in some applications, may reduce the need for external logic. In particular, the 2104 includes an enable input, so 4 2104 chips plus 8 switching transistors can replace an L293 with no need for additional logic. The data sheet microprocessor (formerly Telcom Semiconductor) TC4467 family of CMOS quad driver includes information on how to use the drivers in the family to drive the power MOSFET H-bridges at speeds up to 15 volts. A number of manufacturers make complex H-bridge chips that include a circuit current limiting, which are the subject of the next section. It is also interesting to note that there are a number of 3-phase bridge drivers on the market, able to move Y or delta configured 3-phase permanent magnet steppers. Few of these engines are available, and these chips are not developed with steppers in mind. However, the Toshiba TA7288P, sees GL7438, the TA8400 and TA8405 are clean, and 2 chips of this type, with one of 6 half-bridges ignored, will strictly control 5-winding 10 steps per revolution motor.

Tags: Analysis, Control, Different, Mechanisms, Motor, Operating, Stepping
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The computer and Abacus_ Are they different …?

Tuesday, March 23rd, 2010

The computer and abacus_ they are all different. . . ? Are there any philosophies which charts the interlocking simple circuit to the computer? The early Chinese and frozen juggled the ball through the issues of the abacus, for results of addition and subtraction. Poles more under the abacus, which involve more digits, which would accommodate as many figures as would contain … Civilization at that time had fewer problems to solve. Their level of technology becomes reflects this situation. A specific model has made it easier to manipulate numbers to limit numbers, so simple calculations every day. In a word could equally well meet four poles to represent a thousand bundles figures, save time and energy needed to assemble the same number of issues of reality. In the intrinsic sense, nothing substantial has changed lately. A strip of film on the first computing device, in essence, computers and modern day line up perfectly for a piece of film. Several axioms technology to be incorporated in the racks may confuse the storyboard all-in wiping its artistic beauty. The rapid advancement of technology would lead a person of the caliber of Newton’s Clueless, the mechanism underlying the latest computers operate. We need not end this way: getting a close up of the microprocessor to help equip the index TOGETHER_ the old system and to present the computer with millions of circuits are almost drowned in a sea of electricity shut in their own space. In this universe apparent different elements meet in the infinite permutations in a finite momentum, which is well modulated. Though lifeless, the complex arrangements of circuits to bear witness to the fact that they interpret the language of arithmetic and logic. By ordering a rational individual, the emergence of intelligence evolution takes place for good. The mechanisms of our world … depart from that time. A flash would still run faster than the holder of world record sprint. The microprocessor is an interface between the end of man’s entrance, where it receives instructions_ mostly to store in memory or disk drive_ in the language it is built to discern, and the output that would rapidly receive the results that had been treated in an audiovisual presentation, or graphic details of a literate person would read at first glance. An orderly arrangement of components within the control unit ensures that justice is done on common sense, better known as logic. A computer system which is an embodiment of all the parties mentioned above, entry, exit and the control unit. But its branches could be wider: to control other devices very heart of their channels if possible. For example, experienced pianists know that a computer system, listening to a relevant task on the piano or keyboard, would control the quality, rhythm, pitch … and composing music as he plays in his imagination; saving the embarrassment he may have, his fingers outstretched for long. The keyboard seen in another context does the task of text input into the system, mainly for word processing. Pressing a key with a document or program to a text (witnesses) to be displayed on the screen consists of a sequence of functions, which includes recovering the equivalent magnetic or electric from its location on the hard disk, and printing the electronic version intelligible to the screen. Word characters grouped and allocated to a slot in the disk is a folder, delete the file causes demagnetize a magnet that had been magnetized to slot machines. A copy may be made from the file is when the printer is necessary. Under the overwhelming complexity of miniaturized components, housed in the motherboard, not a chance that the computer system is used for various purposes, including those yet to be excavated. There is strength in numbers, best explains why the edges of modern computer on the abacus to a very wide margin. However unlike evoke both generate the same opinion … there seems to be so much order in the inanimate world. The capacity of the system has evolved rapidly over time, to contain a reasonable fraction of the challenges of civilization. So many things have occurred in some thousands of years which makes them very young, especially on the scale of the evolution of humans. The computer is an amazing tool, after all: it has no will of its own, and he can not imagine himself, but humanity remains dazzled by its correctness, accuracy, efficiency and speed. In fact, it calculates the results at the speed of light, which is a common place in our physical world. Electromagnetic waves, properly corrected by the encoded chips are feasible data generating energy at the least contact with the material. Without the power output, and memory chip, the amount of energy produced in the control unit alone could cause an electrical mishap. Memory loss and a relatively limited communication boils down to efficiency in the process of thought in humans_ they are to blame …? But the answer, the fact remains that we are wired to control the computer and not the reverse: to enjoy its simplicity and beauty of delineating the dimensional array of all knowledge … it can not be placed above the infinite intelligence that is inserted between the lobes of the human brain_ left for his willingness to release it_ dignity, and aesthetic appeal of nature scattered throughout the nations and cultures. Humanity is moving in a vehicle, bolting across a road to computer technology (and a similar ground breaking inventions): As far as the human brain can count, as smart as the human mind can invent, so extraordinary sixth sense may provide. How many are sitting in this big vehicle …? Perhaps a century ago, if we had invented the cybercafe term. . . sensitive that the word is appropriate on hearing_ Many people probably thinks _AS he or she is mad. But we all know now that each syllable of the word in parts properly carried out to create a beautiful image in the eyes of our mind, a system of one or two computers, connected to a network_ as issues of abacus_ with which we can seek world and beyond the touch of a button.

Tags: Abacus_, computer, Different, they
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