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Showing posts from December, 2011

The Fundamentals of PWM Switching Power Supplies

The operation of switching power supplies can be relatively easy to understand. Unlike linear regulators which operate the power transistor in the linear mode, the PWM switching power supply operates the power transistors in both the saturated and cutoff states. In these states, the volt-ampere product across the power transistor is always kept low (saturated, low-V/high-I; and cutoff, Hi-V/No-I). This EI product within the power device is the loss within all the power semiconductors.
This more efficient operation of the PWM switching power supply is done by “chopping” the direct current (dc) input voltage into pulses whose amplitude is the magnitude of the input voltage and whose duty cycle is controlled by a switching regulator controller. Once the input voltage is converted to an ac rectangular waveform, the amplitude can be stepped up or down by a transformer.
Additional output voltages can be derived by adding secondaries to the transformer. Ultimately these ac waveforms are then …

Basic Test Equipment Needed

Power supplies, especially switching power supplies, require the designer to viewparameters not commonly encountered in the other fields of electronics. Aside from ac and dc voltage, the designer must also look at ac and dc current measurements and waveforms, and RF spectrum analysis. Although the vision of large capital expenditures flashes through your mind when this is mentioned, the basic equipment can be obtained for under US $3000. The equipment can be classified as necessary and optional, but somewhere along the line, all the equipment will have to be used whether one buys the items or rents them.

Necessary test equipment
1. A 100MHz or higher bandwidth, time-based oscilloscope. The bandwidth is especially needed for switching power supply design. A digital oscilloscope may miss important transients on some of the key waveforms, so evaluate any digital oscilloscope carefully.
2. 10 : 1 voltage probes for the oscilloscope.
3. A dc/ac volt and ampere multimeter. A true RMS reading me…

A Comment about Power Supply Design Software

There is an abundance of software-based power supply design tools, particularly for PWM switching power supply designs. Many of these software packages were written by the semiconductor manufacturers for their own highly integrated switching power supply integrated circuits (ICs). Many of these ICs include the power devices as well as the control circuitry. These types of software packages should only be used with the targeted products and not for general power supply designs. The designs presented by these manufacturers are optimized for minimum cost, weight, and design time, and the arrangements of any external components are unique to that IC.

There are several generalized switching power supply design software packages available primarily from circuit simulator companies. Caution should be practiced in reviewing all software-based switching power supply design tools. Designers should compare the results from the software to those obtained manually by executing the appropriate desig…

Role of the Power Supply within the System and Design Program

The three major power supply technologies that can be considered within a power supply system are:
1. Linear regulators.
2. Pulsewidth modulated (PWM) switching power supplies.
3. High efficiency resonant technology switching power supplies.
Each of these technologies excels in one or more of the system considerationsmentioned above and must be weighed against the other considerationsto determine the optimum mixture of technologies that meet the needs ofthe final product. The power supply industry has chosen to utilize each of the technologies within certain areas of product applications as detailed in thefollowing.

Linear
Linear regulators are used predominantly in ground-based equipments where
the generation of heat and low efficiency are not of major concern and also where
low cost and a short design period are desired. They are very popular as boardlevel
regulators in distributed power systems where the distributed voltage is less
than 40VDC. For off-line (plug into the wall) products, a po…

High Power Output Amplifier TDA7294

The famous SGS-THOMSON ST Microelectronics has introduced a Hi-Fi DMOS high-power amplifier circuit TDA7294, its sound great taste bile, which due to its internal circuit from input to output are field-effect devices, rounded sound Mild, delicate Rounuan.  However, with its assembly amplifier, only TDA7294 single-output power is only 70 W, BTL access law is 100 W from top to bottom, do not feel that power cushion. The author several tests, used to promote TDA7294-level, direct-drive one to four pairs of high-power transistor parallel, the output of strong currents, the power output of 400 W (mono), and the circuit is simple and no need to debug that can reliably work Basically, the IC has maintained a sound and performance.  Ruzuo The figure below shows, R6 for the feedback resistor, the author of the value in debugging 22 k Ω more appropriate, R6 also decided this circuit gain, the gain value will increase.  Quiescent current depends on the power of R7, R8, when its value…

Toshiba Thrive Tablet Computer

The Toshiba Thrive computer tablet uses Android 3.1 “Honeycomb” interface, allowing users to enjoy customizable desktops for widgets and shortcuts.  In terms of UI, the device is quite notable not only because it can be customized but also since the icons such as alerts, clocks, and battery level are placed with the convenience of users in mind.

As with most new Android-powered tablets, the Thrive features multi-tasking button on the bottom left of the taskbar, allowing users to easily scroll the list of thumbnails that represent applications.  And to further deliver a better UI, it has two virtual keyboards: the Swype which allows people to type quicker by tracing lines between letters, and the standard Android.

In terms of design, the computer tablet is heavier and thicker than its rivals such as the Apple iPad 2, Samsung Galaxy Tab 10.1, and Asus Eee Pad Transformer with its 10.75 x 6.7 x 0.6 inches and 1.6 pounds chassis.  But despite its cumbersome appearance, it has a…

Sony Alpha NEX-C3 Camera

The Sony Alpha NEX-C3 is a 16.2-megapixel digital camera that is smaller and lighter than its predecessor despite having an improved resolution and ability to provide impressive images even in low-light environment; this is possible with the removal flash in addition to technologies almost comparable to a D-SLR.

But just like its predecessors, the digital camera has interchangeable lens (18-55mm zoom lens or 16mm pancake prime lens) and pop-up flash.
The 2.4 x 4.4 x 1.3 inches (HWD) camera weighs 9.8 ounces, lighter than most of its rivals with almost the same size and features.  The standard 18-55mm kit zoom lens is almost the same size and weight of D-SLR’s (7 ounces and 2.4 x 2.5-inch body), while the 16mm pancake prime lens weighs just 2.4 ounces.

In terms of speed, the NEX-C3 can compete with most D-SLRs with its ability to take initial shot in 1.5 seconds.  And when it is set to focus, the camera averages approximately 0.5 second between pushing the shutter button and …

Lavnav helps you aim straight at night

Do you envy those who are able to sleep through the night without having to worry about getting up halfway in the middle in order to take a leak? Well, I suppose all the shuffling around is all right when you’re single, but some of us who are married might have spouses who are light sleepers and do not take it too kindly whenever you keep on getting up and turning on the lights just to get some relief from all the pressure that’s building up in your bladder.

Well, how about getting the �16.99 Lavnav instead? Yes sir, this unique gizmo will do away with the unpleasant experience of getting yourself half-blind when you turn on the bathroom lights with a 1,000-watt light bulb in place. All you need to do is stick the Lavnav onto the inside of your lavatory and you’re good to go – after all, the motion sensor kicks itself into action the moment it detects anyone within the vicinity. Heck, when the seat is up, it will be red in color, but goes green when the seat is left down.

Veebeam HD brings Internet to your TV

Smart TVs have been around for some years now, but it is safe to say that they haven’t really caught on just yet in the mass market. Well, for those who are sick and tired of watching videos as well as playing catchup on your TV programmes on a much smaller notebook display, here is the Veebeam HD to solve your woes. With this little puppy, you are able to effortlessly stream just about any content from your notebook to your home TV. You name it – live sports, streaming music, movie websites, home videos from your hard drive, the possibilities are more or less endless as long as you can view it on your computer.

Since the Veebeam HD works over the wireless spectrum, you have one less cable to worry about when it comes to keeping your home clutter-free and neat. All you need to do is plug in the USB receiver into the funky-looking �139.99 Veebeam HD unit, hook it up to your TV while plugging the separate USB antenna into your computer or notebook – it doesn’t matter wheth…

Smartfish Mouse Pad Travel Pouch

All mice these days no longer feature a trackball, relying on an optical sensor instead. Unfortunately, the optical sensor’s limitations are there, as it will not work across all surfaces, especially glass. That’s when you need an impromptu mouse pad, which makes the Smartfish Mouse Pad Travel Pouch a real genius as a practical traveling companion.
This mouse pad features a smooth 9� diameter surface work area for you to mouse around with, and once you’re done with your work, you can always slip the mouse inside, zip it up, and it doubles up as a protective pouch instead.
The nclusion of padded neoprene ensures your accessories (and mouse, of course) inside remains safe and sound when tucked away, and you can also opt to hang it from your backpack or suitcase for easy accessibility via the snap handle. At just $14.95 a pop, the Smartfish Mouse Pad Travel Pouch will come in blue and black shades from early next month onwards.

Portal 2 PotatOS Science Kit

What are some of the memories that you carry around from playing Portal 2? For some of us, it would be toting the PotatOS around the test facility, where you felt this unnatural bond as though you were kindred spirits, never mind that this is not the case.
Well, for folks who skipped the children’s Science Fair at Aperture Labs, here is something that might just redeem your absence – the $29.99 Portal 2 PotatOS Science Kit. Yes sir, just about everything that is required by you is packed into a handy Portal 2 PotatOS Science Kit, where it even sports a miniature science fair poster complete with brand new content from Valve’s writing team!
The only thing that you will need to come up with would be your very own potato, but that should not be too hard to get, right? If you’re great at following instructions, it will take mere minutes to transform your potato into your very own PotatOS, where it will light up and send verbal repartees your way, just like in the game. Nice t…

Archos 35 Home Connect.

Archos intends to further push the envelope when it comes to technological boundaries as well as innovation with the introduction of their latest device, the Archos 35 Home Connect.
This is an Android-powered web radio that was specially designed for the home user. Touted to be the most advanced Android-based web radio in the market (which makes perfect sense after all, since how many web radios that run on the Android OS do you see hanging around store shelves, virtual or otherwise?), the Archos 35 Home Connect is perfectly sized to deliver streaming radio and music anywhere at home, ranging from the bedroom to the kitchen, bathroom or kids room.
Being diminutive in size certainly makes it a whole lot easier to tote around, and the Archos 35 Home Connect will boast Wi-Fi connectivity as well as amazing audio quality, once again lending wisdom to the adage that one ought not to judge a book by its cover – and in this case, the audio quality by its size. Let us take a c…

Quad Lock Case announced

Annex Products has announced the rollout of its Quad Lock Case, which is touted to be the ultimate multipurpose mounting system for your precious iPhone.
Just what is the Quad Lock Case capable of? For starters, this is touted to be a safe and easy mounting solution which is capable of mounting itself to just about any surface, ensuring that your iPhone remains in a convenient position regardless of either it being in a portrait or landscape mode, letting you view your favorite photos, enjoy movies and read news, hands-free.
The Quad Lock Case Mount comes in an ultra slim form factor, where it is made up of tough polycarbonate plastic in order to help protect your iPhone’s back during everyday use. You know what they say – the simpler something is, the more beautiful it becomes, and that is exactly the case (pun not intended) with the Quad Lock Case Mount. Featuring a built-in holder which enables it to snap securely on to any of the Quad Lock Mounts, you need not worry a…

Diodes 90W mosfet controller rated to 25V

Diodes 90W mosfet controller rated to 25VDiodes is offering a 25V-rated synchronous MOSFET controller for notebook and laptop power supply designs of 90W and above.

Designed to replace Schottky diodes in flyback converters, the ZXGD3104N8 is claimed to increase power supply efficiency by up to 3.5% through a reduction in rectifier losses of up to 70%. As a result, the device helps power supplies more easily attain the 87% Energy Star V2.0 rating.With its wide operating voltage range of 5V to 25V, this SO8-packaged mosfet controller is able to be directly powered from the adaptor’s 19V supply rail.
The ZXGD3104N8’s proportional gate-drive operation guards against premature mosfet turn-off as the drain current decays, thereby maximising circuit efficiency and ensuring body diode conduction losses are minimized.

This, combined with the short turn-off propagation delay of typically 15ns, helps to maximize power supply circuit efficiency.

Plastic circuitry breakthrough may revolutionizeelectronics industry

Plastic circuitry breakthrough may revolutionizeelectronics industry
Researchers from the University of Cambridge's Cavendish Laboratory have a chance to revolutionize the electronics industry if they can develop plastic semiconductors. The idea is to replace the silicon wafers in standard microchips with layers or circuitry on plastic substrates. While the concept of plastic semiconductors may seem like a pipe dream, Cambridge-based startup Plastic Logic has been talking about commercializing the technology since 2000. The company is putting money where it's mouth is, too, as it has more than $100 million worth of investment funds for a factory that it plans to open in Dresden, Germany.
The technology has "tremendous potential," said Morry Marshall, vice-president for strategic technologies at Phoenix semiconductor research group Semico, adding that it was a "breakthrough that is waiting to happen." The final product should be a plastic sheet roughly the same …

First Molybdenite Microchip

First Molybdenite Microchip

Molybdenite, a new and very promising material, can surpass the physical limits of silicon. EPFL scientists have proven this by making the first molybdenite microchip, with smaller and more energy efficient transistors.After having revealed the electronic advantages of molybdenite, EPFL researchers have now taken the next definitive step. The Laboratory of Nanoscale Electronics and Structures (LANES) has made a chip, or integrated circuit, confirming that molybdenite can surpass the physical limits of silicon in terms of miniaturization, electricity consumption, and mechanical flexibility.

"We have built an initial prototype, putting from two to six serial transistors in place, and shown that basic binary logic operations were possible, which proves that we can make a larger chip," explains LANES director Andras Kis, who recently published two articles on the subject in the scientific journal ACS Nano.
In early 2011, the lab unveiled t…

UltraSonic Switch

UltraSonic Switch
Circuit of a new type of remote control switch is described here. This circuit functions with inaudible (ultrasonic) sound. Sound of frequency up to 20 kHz is audible to human beings. The sound of frequency above 20 kHz is called ultrasonic sound. The circuit described generates (transmits) ultrasonic sound of frequency between 40 and 50 kHz. As with any other remote control system this cirucit too comprises a mini transmitter and a receiver circuit. Transmitter generates ultrasonic sound and the receiver senses ultrasonic sound from the transmitter and switches on a relay. The ultrasonic transmitter uses a 555 based astable multivibrator.

It oscillates at a frequency of 40-50 kHz. An ultrasonic transmitter transducer is used here to transmit ultrasonic sound very effectively. The transmitter is powered from a 9-volt PP3 single cell. The ultrasonic receiver circuit uses an ultrasonic receiver transducer to sense ultrasonic signals. It also uses a two-stage amplifier, …

FANCY CHRISTMAS LIGHT

FANCY CHRISTMAS LIGHT

This simple and inexpensive circuit built around a popular CMOS hex inverter IC CD4069UB offers four sequential switching outputs that may be used to control 200 LEDs (50 LEDs per channel), driven directly from mains supply. Input supply of 230V AC is rectified by the bridge rectifiers D1 to D4. After fullwave rectification, the average output voltage of about 6 volts is obtained across the filter comprising capacitor C1 and resistor R5. This supply energises IC CD4069UB.


All gates (N1-N6) of the inverter have been utilised here. Gates N1 to N4 have been used to control four high voltage transistors T1 to T4 (2N3440 or 2N3439) which in turn drive four channels of 50 LEDs each through current limiting resistors of 10-kilo-o Base drive of transistors can be adjusted with the help of 10-kilo-ohm pots provided in their paths. Remaining two gates (N5 and N6) form a low frequency oscillator. The frequency of this oscillator can be changed through pot VR1. When pot VR1 …

A LOW DISTORTION AUDIO PREAMPLIFIER

A LOW DISTORTION AUDIO PREAMPLIFIER
In an audio amplifier the quality of sound depends upon a number of factors, e.g. quality of active and passive components, circuit configuration, and layout. To an extent, the selection of components depends on the constructor’s budget. The discrete active components like transistors have been increasingly replaced by linear ICs, making the task of designer easier. With the passage of time, the general-purpose op-amps like LM741, which were being used in audio/hi-fi circuits, have become The preamplifier circuit presented here is based on a dual precision op-amp for the construction of a low distortion, high quality audio preamplifier.


A dual op-amp OPA2604 from Burr-Brown is used for all the stages. The FET input stage op-amp was chosen in this context it is worthwile to mention another popular bi-polar architecture op-amp, the NE5534A. It has, no doubt, an exceptionally low noise figure of 4nV/ÖHz but rest of the specifications compared to OPA260…

VHF AUDIO VIDEO TRANSMITTER

VHF AUDIO VIDEO TRANSMITTER
The circuit presented here is a simple audio/video transmitter with a range of 3 to 5 metres. The A/V signal source for the circuit may be a VCR, a satellite receiver or a video game etc. The circuit uses inexpensive components which are easily available in the market.A block diagram showing the principle of its operation and complete circuit diagram are shown in the figure. A mixer which also operates as an oscillator at VHF (H) channel 5 TV frequency is amplitude modulated by video signal and mixed with frequency mo enna, contains video carrier frequency of 175.25 Mhz and audio carrier frequency of 180.75 Mhz.

The circuit consists of transistor T1 with its resonant tuned tank circuit formed by inductor L1 and trimmer capacitor VC1, oscillating at VHF (H) channel 5 frequency. Transistor T2 with its tuned circuit formed using SIF coil and inbuilt capacitor forms oscillator. The audio signal applied at the input to T2 results into frequency modulation of 5.5…

INFRARED TOY CAR MOTOR CONTROLLER

INFRARED TOY CAR MOTOR CONTROLLER This add-on circuit enables remote switching on/off of battery-operated toy cars with the help of a TV/ video remote control handset operating at 30–40 kHz..  When the circuit is energised from a 6V battery, the decade counter CD4017 (IC2), which is configured as a toggle flip-flop, is immediately reset by the power-onreset combination of capacitor C3 and resistor R6.
LED1 connected to pin 3 (Q0) of IC2 via resistor R5 glows to indicate the standby condition. In standby condition, data output pin of the integrated infrared receiver/demodulator (SFH505A or TSOP1738) is at a high level (about 5 volts) and transistor T1 is ‘off’ (reverse biased). The monostable wired around IC1 is inactive in this condition.

When any key on the remote control handset is depressed, the output of the IR receiver momentarily transits through low state and transistor T1 conducts. As a result, the monostable is triggered and a short pulse is applied to the clock input (pin 1…

Audio Amplifier

Audio Amplifier
The principal component of the amplifier kit is the LM 386 IC. This IC is specifically designed as a low wattage amplifier for small scale projects. The signal enters through R1, the 10Kohm potentiometer. This also serves as a volume control for the circuit. The signal is introduced to pin 3 of the IC. The amplifier output is passed directly to speaker through C2. The capacitor is used to isolate the speaker from the dc power that drives the amplifier.

The circuit composed of R2, the 1K ohm resistor, and C1 the 10uF capacitor, establishes the gain of the amplifier. For this circuit, the gain is set at 50.To increase the gain you can either increase the value of the capacitor or decrease the value of the resistor.
The 0.uF capacitor placed across the power source is used to eliminate noise that can be generated by power source.

Semiconductors

Semiconductors  Conductivity in between those of metals and insulators.Conductivity can be varied over orders of magnitude by changes in temperature, optical excitation, and impurity content (doping).Generally found in column IV and neighboring columns of the periodic table.Elemental semiconductors: Si, Ge.Compound semiconductors:

Binary :
GaAs, AlAs, GaP, etc. (III-V).
ZnS, ZnTe, CdSe (II-VI).
SiC, SiGe (IV compounds).
Ternary : GaAsP.
Quaternary : InGaAsP.Si widely used for rectifiers, transistors, and ICs.III-V compounds widely used in optoelectronic and high-speed applications.Applications Integrated circuits (ICs) SSI, MSI, LSI, and VLSI.Fluorescent materials used in TV screens II-VI (ZnS).Light detectors InSb, CdSe, PbTe, HgCdTe.Infrared and nuclear radiation detectors Si and Ge.Gunn diode (microwave device) GaAs, InP.Semiconductor LEDs GaAs, GaP.Semiconductor LASERs GaAs, AlGaAs.Energy Gap Distinguishing feature among metals, insulators, and semiconductors.Determin…

Filter Characteristics

 FilterCharacteristics
If an ideal low-pass filter existed, it would completely eliminate signals above the cutoff frequency, and perfectly pass signals below the cutoff frequency. In real filters, various trade-offs are made to get optimum performance for a given application.
Butterworth filters are termed maximally-flat-magnitude-response filters, optimized for gain flatness in the pass-band. the attenuation is –3 dB at the cutoff frequency. Above the cutoff frequency the attenuation is –20 dB/decade/order. The transient response of a Butterworth filter to a pulse input shows moderate overshoot and ringing. Bessel filters are optimized for maximally-flat time delay (or constant-group delay). This means that they have linear phase response and excellent transient response to a pulse input. This comes at the expense of flatness in the pass-band and rate of rolloff. The cutoff frequency is defined as the –3-dB point. Chebyshev filters are designed to have ripple in the pass-band, but steeper rollo…

To study DC potentiometer.

Aim:- To study DC potentiometer. Apparatus:- Power supply,(0-50v) Battery,(0-30V) Resister-100W Circuit Diagram :- Theory:- The potentiometer although not consider a bridge has circuit that using a simple circuit thermo becomes identical to the whetstone bridge. The potentiometer is a device for measuring the voltage while presenting a very high impedance to the voltage source under the Test. The variable resister R1 is the precision device that can be set to an accurate value. the resister is adjusted so that no current is flow through the galvanometer. which is the similar to balancing the bridge. At this point the zero current flow several important characteristics of the potentiometer cab be determine. Result:- To study the working of the DC potentiometer. Viva questions:- 1) What is the importance of std.cell of the Dc potentiometer? 2) How the Unknown emf is calculated by the Dc Potentiometer

Measurement of the unknown capacitance schering bridge method.

Aim:- Measurement of the unknown capacitance schering bridge method. Apparatus:- Sharing bridge kit digital multimeter, patch cords, Circuit Diagram:- Theory:- The schering bridge one of the most important ac bridge is used the extensively for the measurement of capacitors. In the schering bridge the arm 1 now contains a parallel combination of the resistor and the capacitor and standard arm contain only one capacitor. The standard capacitor is usually a standard high quality mica capacitor. in the balance condition of the bridge the sum of the phase angles of the arms 1 and 4 is equal the sum of the phase angle of arms 2 and 3.at the balance in condition there is no current flow in the galvanometer. The balance equation is derived in the usual manner, and by substituting the corresponding impendence and the admittance the value of the unknown capacitor and the resister is find as given below. Cx=C3(R1/R2). Rx=R2(C1/C2) Procedure: - 1) Study the circuit provided on the front panel on the kit. 2) Connect t…