DIGITAL SYSTEMS

CANON POWERSHOT E1 DIGITAL CAMERA

2009-01-13T00:12:00.000-08:00

CANON POWERSHOT E1 DIGITAL CAMERA 10MP+4GB+Tripod+SP

Type of Camera
Type of Camera Compact digital still camera with built-in flash, 4x Optical/4x Digital/16x Combined Zoom with Optical Image Stabilizer System

Image Capture Device
Type :- 10.0 Megapixel, 1/2.3-inch type Charge Coupled Device (CCD)
Total Pixels :- Approx. 10.3 Megapixels
Effective Pixels :-Approx. 10.0 Megapixels

Lens
Focal Length :- 6.2-24.8mm f/2.7-5.6 (35mm film equivalent: 35-140mm)
Digital Zoom :- 4x
Focusing Range :- Normal: 1.6 ft./50cm-infinity
Macro :- 1.2 in.-1.6 ft./3-50cm (W), 1.0-1.6 ft./30-50cm (T)
Autofocus System :- TTL Autofocus

Canon IXUS 870 IS Digital Camera

2009-01-13T00:05:00.000-08:00

Canon IXUS 870 IS Digital Camera

Canon IXUS 870 IS digital camera features with 10MP sensor, DIGIC4 Image processor, 4x 28mm wide-angle optical zoom lens, optical image stabiliser, anti-blur technology, face detection, i-contrast (adjust shadow or darker region) and 3 inch LCD screen.

In tha box

Canon Powershot G10 Digital Camera

2009-01-12T23:37:00.000-08:00

Canon Powershot G10 Digital Camera
Canon Powershot G10 digital camera is equipped with 14.7MP sensor, DIGIC 4 image processor, 5X 28mm wide-angle lens with optical image stabiliser, anti-blur technology, 3 inch LCD screen with view finder, i-contrast, face detection, support RAW and DPP formats.

13.Car anti theft wireless alarm.

2009-01-06T18:30:00.000-08:00

This FM radio-controlled anti- theft alarm can be used with any vehicle having 6- to 12-volt DC supply system. The mini VHF, FM transmitter is fitted in the vehicle at night when it is parked in the car porch or car park. The receiver unit with CXA1019, a single IC-based FM radio module, which is freely available in the market at reasonable rate, is kept inside. Receiver is tuned to the transmitter's frequency. When the transmitter is on and the signals are being received by FM radio receiver, no hissing noise is available at the output of receiver. Thus transistor T2 (BC548) does not conduct. This results in the relay driver transistor T3 getting its forward base bias via 10k resistor R5 and the relay gets energised. When an intruder tries to drive the car and takes it a few metres away from the car porch, the radio link between the car (transmitter) and alarm (receiver) is broken. As a result FM radio module gene-rates hissing noise. Hissing AC signals are coupled to relay switching circ- uit via audio transformer. These AC signals are rectified and filtered by diode D1 and capacitor C8, and the resulting positive DC voltage provides a forward bias to transistor T2. Thus transistor T2 conducts, and it pulls the base of relay driver transistor T3 to ground level. The relay thus gets de-activated and the alarm connected via N/C contacts of relay is switched on. If, by chance, the intruder finds out about the wireless alarm and disconnects the transmitter from battery, still remote alarm remains activated because in the absence of signal, the receiver continues to produce hissing noise at its output. So the burglar alarm is fool-proof and highly reliable.

12.Simple Analog to Digital Converter

2009-01-04T17:13:00.000-08:00

Normally analogue-to-digital con-verter (ADC) needs interfacing through a microprocessor to convert analogue data into digital format. This requires hardware and necessary software, resulting in increased complexity and hence the total cost.

The circuit of A-to-D converter shown here is configured around ADC 0808, avoiding the use of a microprocessor. The ADC 0808 is an 8-bit A-to-D converter, having data lines D0-D7. It works on the principle of successive approximation. It has a total of eight analogue input channels, out of which any one can be selected using address lines A, B and C. Here, in this case, input channel IN0 is selected by grounding A, B and C address lines.

Usually the control signals EOC (end of conversion), SC (start conversion), ALE (address latch enable) and OE (output enable) are interfaced by means of a microprocessor. However, the circuit shown here is built to operate in its continuous mode without using any microprocessor. Therefore the input control signals ALE and OE, being active-high, are tied to Vcc (+5 volts). The input control signal SC, being active-low, initiates start of conversion at falling edge of the pulse, whereas the output signal EOC becomes high after completion of digitisation. This EOC output is coupled to SC input, where falling edge of EOC output acts as SC input to direct the ADC to start the conversion.

As the conversion starts, EOC signal goes high. At next clock pulse EOC output again goes low, and hence SC is enabled to start the next conversion. Thus, it provides continuous 8-bit digital output corresponding to instantaneous value of analogue input. The maximum level of analogue input voltage should be appropriately scaled down below positive reference (+5V) level.
The ADC 0808 IC requires clock signal of typically 550 kHz, which can be easily derived from an astable multivibrator constructed using 7404 inverter gates. In order to visualise the digital output, the row of eight LEDs (LED1 through LED8) have been used, wherein each LED is connected to respective data lines D0 through D7. Since ADC works in the continuous mode, it displays digital output as soon as analogue input is applied. The decimal equivalent digital output value D for a given analogue input voltage Vin can be calculated from the relationship

11. Led display digital Voltmeter

2009-01-03T18:02:00.000-08:00

front side & back side

Description

This is an easy to build, but nevertheless very accurate and useful digital voltmeter. It has been designed as a panel meter and can be used in DC power supplies or anywhere else it is necessary to have an accurate indication of the voltage present. The circuit employs the ADC (Analogue to Digital Converter) I.C. CL7107 made by INTERSIL. This IC incorporates in a 40 pin case all the circuitry necessary to convert an analogue signal to digital and can drive a series of four seven segment LED displays directly. The circuits built into the IC are an analogue to digital converter, a comparator, a clock, a decoder and a seven segment LED display driver. The circuit as it is described here can display any DC voltage in the range of 0-1999 Volts.

Specifications-Characteristics

Supply Voltage: ............. +/- 5 V (Symmetrical)
Power requirements: ..... 200 mA (maximum)
Measuring range: .......... +/- 0-1,999 VDC in four ranges
Accuracy: ....................... 0.1 %

- Small size
- Easy construction
- Low cost.
- Simple adjustment.
- Easy to read from a distance.
- Few external components.

How to do work

An Analogue to Digital Converter, (ADC from now on) is better known as a dual slope converter or integrating converter. This type of converter is generally preferred over other types as it offers accuracy, simplicity in design and a relative indifference to noise which makes it very reliable. The operation of the circuit is better understood if it is described in two stages. During the first stage and for a given period the input voltage is integrated, and in the output of the integrator at the end of this period, there is a voltage which is directly proportional to the input voltage. At the end of the preset period the integrator is fed with an internal reference voltage and the output of the circuit is gradually reduced until it reaches the level of the zero reference voltage. This second phase is known as the negative slope period and its duration depends on the output of the integrator in the first period. As the duration of the first operation is fixed and the length of the second is variable it is possible to compare the two and this way the input voltage is in fact compared to the internal reference voltage and the result is coded and is send to the display.

10. Frequency To Voltage Converter: Change Your Voltmeter To Frequency Meter

2009-01-01T17:26:00.000-08:00

Frequency meter can be used in speed sensor, tachometer, or any measurement of repetitive signals. This frequency to voltage converter (FVC) can be used to turn your analog or digital voltmeter into a tachometer. The circuit’s schematic diagram is shown below.

The circuit consist of three blocks. The first block is a squarer, change the input signal to a square wave. This block is protected from high voltage input up to 400V , but remember this works only if the capacitor C1 is rated for 400V. This input impedance is approximately 560k, so it’s safe to connect your ignition pick-up coil in parallel with your CDI (capacitor discharge ignition) circuit without any problem. The supply is protected from voltage spike by Zener diode D3.

The second block is a retriggerable monostable multi vibrator. This monostable multi vibrator convert the pulses to give fixed width output, so the average output voltage will be independent of the duty factor of the input pulses/waveform, but solely depends on the input frequency. The pulse width is determined by R9+R5 and C4. At minimum value of R9, the monostable multi vibrator output pulse width will be 0.2 * 4700 * 22e-6 * ln(12) = 5.51e-5 , and this setting will convert the frequency of 19.460kHz to 12 Volt Output. This give conversion factor of 1.622kHz/Volt. If you set R9 to the maximum value (100k) then the pulse width of the monostable multi vibrator output will be 1.145 mS. This setting will give maximum output voltage 12V at 874Hz, or about 72.8Hz per Volt conversion rate. If you use for tachometer application, this wide rage adjustment will accommodate almost any types of engines.

The last block is a first order low pass filter around U2, about 0.1 second time constant set by R6 and C5. With this slow settling time, you can’t read any frequency below or near 10Hz, but it’s OK for many application. Although the schematic diagram doesn’t show a decoupling capacitor for bypassing supply line noise for U3, it’s good to add a 100nF cap as close as possible to U3 power supply pin ( pin 8 and 16), since a monostable multi vibrator is sensitive to this kind of noise.

9. AC Power Control Circuits FET Circuits

2008-12-30T16:47:00.000-08:00

1.White LED Strings of AC Powered

A while back a guy by the name of Ken Schultz sent me a simple drawing of how he connected a string of 30 LEDs, to make a nice under the counter accent light, powered by 120vac. He wired the strings in two series sections of 15 LED each, but wired in opposite directions. He then used just one capacitor to limit the AC current through the two stings. I looked at the circuit and decided that it seemed quite reasonable. The only change I decided to make was to add a metal oxide resistor in series with the capacitor, to act as fuse and to limit the peak current, should there be a voltage spike on the AC line. With the two strings of 15, the current is first pumped through one series string, then as the AC line polarity changes, it flows through the second string. Since the capacitor acts as a constant current source, you can use other string numbers. The capacitor value shown keeps the current limited to about 20ma for the LEDs. In Europe and Australia, where the line frequency is 50Hz, you may see a noticeable strobing of the LEDs, if there is substantial separation between the two different polarity strings.

2. CHARGE COUPLED BI-DIRECTIONAL POWER MOSFET RELAY

The circuit uses an inexpensive C-MOS inverter package and a few small capacitors to drive two power MOS transistors from a 12v to 15v supply. Since the coupling capacitor values used to drive the FETs are small, the leakage current from the power line into the control circuit is a tiny 4uA. Only about 1.5mA of DC is needed to turn on and off 400 watts of AC or DC power to a load

2.SOLID STATE RELAY REQUIRES ONLY 50uA DRIVE CURRENT

This circuit demands a control current that is 100 times smaller than that needed by a typical optically isolated solid state relays. It is ideal for battery-powered systems. Using a combination of a high current TRIAC and a very sensitive low current SCR, the circuit can control about 600 watts of power to load while providing full isolation and transient protection.

8.7490 Decade Counter

2008-12-28T06:33:00.000-08:00

The 7490 integrated circuit counts the number of pulses arriving at its input.
The number of pulses counted (up to 9) appears in binary form on four pins of the ic.
When the tenth pulse arrives at the input, the binary output is reset to zero (0000) and a single pulse appears at another output pin.
So for ten pulses in there is one pulse out of this pin.
The 7490 therefore divides the frequency of the input by ten.
If this pulse is applied to the input of a second 7490 then this second ic will count the pulses from the first ic.
It will give one pulse out after 100 pulses have been applied to the first ic.
The 7490 can be connected to divide by other values.

7. Input signals & Out put signals of Gates

2008-12-28T06:04:00.000-08:00

6. Digital Signals and Logic Gates

2008-12-23T20:15:00.000-08:00

Engineers know that it is easier to design two-state devices than multi-state devices. In logic systems, variables, circuits, statements, etc., can be treated in one of two distinct states: true or false, yes or no, on or off, present or absent, energized or not energized, conducting or non-conducting, high voltage or low voltage, and so on.

In digital electronics, we distinguish two distinct values of voltage, VH corresponding to the higher of the two voltages and VL corresponding to the lower of the two voltages. There are three ways in which we can assign binary values to these voltages:

1. Positive logic assignment: True [ 1 ] : VH False [0]: VL

2. Negative logic assignment: True [1]: VL False [0]: VH

3. Mixed logic assignment: Allow the designers to use positive
Or negative logic at any point in
Their design, as they desire.

5. Calculation of Binary

2008-12-22T20:09:00.000-08:00

Addition of binary

Binary of Multiplication

4.Conversions

2008-12-21T20:22:00.000-08:00

1. Binary to decimal conversion
The computer is a binary beast. We want to go from the one-fingered digital box to the ten-fingered human being and convert binary to denary(base 10) numbers. This is how it works, for instance, binary 10010 is calculated as 1*16+0*8+0*4+1*2+0*1 = decimal 18. Just because it's easy, let's throw in hexadecimal and octal results too. The added bonus is the almost foolproof entry of data
2. Decimal To Binary Conversion
To convert a decimal number to binary, first subtract the largest possible power of two, and keep subtracting the next largest possible power form the remainder, marking 1s in each column where this is possible and 0s where it is not.

3. Binary number system

2008-12-20T20:09:00.000-08:00

Base two has several other names, including the binary positional numeration system and the dyadic system. Many civilizations have used the binary system in some form, including inhabitants of Australia, Polynesia, South America, and Africa. Ancient Egyptian arithmetic depended on the binary system. Records of Chinese mathematics trace the binary system back to the fifth century and possibly earlier. The Chinese were probably the first to appreciate the simplicity of noting integers as sums of powers of 2, with each coefficient being 0 or 1. For example, the number 10 would be written as 1010:

10= 1 x 23 + 0 x 22 + 1 x 21 + 0 x 20

Users of the binary system face something of a trade-off. The two-digit system has a basic purity that makes it suitable for solving problems of modern technology. However, the process of writing out binary numbers and using them in mathematical computation is long and cumbersome, making it impractical to use binary numbers for everyday calculations. There are no shortcuts for converting a number from the commonly used denary scale (base ten) to the binary scale.

Over the years, several prominent mathematicians have recognized the potential of the binary system. Francis Bacon (1561-1626) invented a "bilateral alphabet code," a binary system that used the symbols A and B rather than 0 and 1. In his philosophical work, The Advancement of Learning , Bacon used his binary system to develop ciphers and codes. These studies laid the foundation for what was to become word processing in the late twentieth century. The American Standard Code for Information Interchange (ASCII), adopted in 1966, accomplishes the same purpose as Bacon's alphabet code. Bacon's discoveries were all the more remarkable because at the time Bacon was writing, Europeans had no information about the Chinese work on binary systems.

A German mathematician, Gottfried Wilhelm von Leibniz (1646-1716), learned of the binary system from Jesuit missionaries who had lived in China. Leibniz was quick to recognize the advantages of the binary system over the denary system, but he is also well known for his attempts to transfer binary thinking to theology. He speculated that the creation of the universe may have been based on a binary scale, where "God, represented by the number 1, created the Universe out of nothing, represented by 0." This widely quoted analogy rests on an error, in that it is not strictly correct to equate nothing with zero.

The English mathematician and logician George Boole (1815-1864) developed a system of Boolean logic that could be used to analyze any statement that could be broken down into binary form (for example, true/false, yes/no, male/female). Boole's work was ignored by mathematicians for 50 years, until a graduate student at the Massachusetts Institute of Technology realized that Boolean algebra could be applied to problems of electronic circuits. Boolean logic is one of the building blocks of computer science, and computer users apply binary principles every time they conduct an electronic search.

The binary system works well for computers because the mechanical and electronic relays recognize only two states of operation, such as on/off or closed/open.

Operational characters 1 and 0 stand for 1 = on = closed circuit = true 0 = off = open circuit = false

The telegraph system, which relies on binary code, demonstrates the ease with which binary numbers can be translated into electrical impulses. The binary system works well with electronic machines and can also aid in encrypting messages. Calculating machines using base two convert decimal numbers to binary form, then take the process back again, from binary to decimal.

The binary system, once dismissed as primitive, is thus central to the development of computer science and many forms of electronics. Many important tools of communication, including the typewriter, cathode ray tube, telegraph, and transistor, could not have been developed without the work of Bacon and Boole. Contemporary applications of binary numerals include statistical investigations and probability studies. Mathematicians and everyday citizens use the binary system to explain strategy, prove mathematical theorems, and solve puzzles.

2. Decimal number system

2008-12-19T19:55:00.000-08:00

1.Decimal number
The number system we use every day, based on 10 digits (0,1,2,3,4,5,6,7,8,9).

Position is important, with the first position being units, then next on the left being tens, then hundreds and so on

2.Decimal Point

A point or dot used to separate the whole number part from the fractional part of a number.

Example: in the number 36.9 the dot separates the 36 (the whole number part from the 9 (the fractional part, which really means 9/10)

1.Basic Electronic circuits

2008-12-18T19:24:00.000-08:00

1. Types of circuits

1. Analog circuits

Most analog electronic appliances, such as radio receivers, are constructed from combination's of a few types of basic circuits. Analog circuits use a continuous range of voltage as opposed to discrete levels as in digital circuits.
The number of different analog circuits so far devised is huge, especially because a 'circuit' can be defined as anything from a single component, to systems containing thousands of components.

Analog circuits are sometimes called linear circuit although many non-linear effects are used in analog circuits such as mixers, modulators, etc. Good examples of analog circuits include vacuum tube and transistor amplifiers, operational amplifiers and oscillators.

Some analog circuitry these days may use digital or even microprocessor techniques to improve upon the basic performance of the circuit. This type of circuit is usually called "mixed signal."

Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear and non-linear operation. An example is the comparator which takes in a continuous range of voltage but puts out only one of two levels as in a digital circuit. Similarly, an over driven transistor amplifier can take on the characteristics of a controlled switch having essentially two levels of output.

2. Digital circuits

Digital circuits are electric circuits based on a number of discrete voltage levels. Digital circuits are the most common physical representation of Boolean algebra and are the basis of all digital computers. To most engineers, the terms "digital circuit", "digital system" and "logic" are interchangeable in the context of digital circuits. In most cases the number of different states of a node is two, represented by two voltage levels labeled "Low"(0) and "High"(1). Often "Low" will be near zero volts and "High" will be at a higher level depending on the supply voltage in use.

Computer electronic clocks and programmable logic controllers (used to control industrial processes) are constructed of digital circuits. digital signal processors are another example.

2.advantage of digital systems analog system

Computers are digital devices, meaning they perform all calculations using ones and zeros. This method of computing is referred to as the "binary system," and is the heart of all digital technology. Devices such as hard drives, CD recorders, and Mini DV camcorders are digital devices, and therefore record data digitally, as ones and zeros.

VCRs, tape players, and record players, on the other hand, are analog devices. This is because they record data linearly from one point to another. Imagine a bumpy line moving from left to right -- that is what an analog audio recording would look like. Analog devices read the media, such as tapes or records, by scanning the physical data off the media.

For example, a record player reads the bumps and dips in the grooves of the record and translates the information into an audio signal. An audio CD player, however, reads ones and zeros off a compact disc and translates that information into an audio signal. However, the ones and zeros only estimate the actual soundwave, whereas a record player records the exact sound. When you hear terms like "sampling rate" or "bit rate," these refer to how many times per second the digital signal is sampled. The higher the number, the more accurate the estimate is, which translates into higher quality sound or video.

So why is digital technology used if analog provides a better representation of the recorded information? Well, since computers perform digital computations, they can only work with digital media. Therefore, all analog audio or video media must be converted to digital to work on a computer. Once the information is digital, computers can be used to edit the data and create effects that were never possible with analog media. Digital media is non-linear, which means it can be edited or played back starting at any point, which can be a huge timesaver compared to working with tape. Digital information also does not "wear out" after repeated use like tapes or records do, which results in much better longevity for digital media.

To summarize, a digital signal is an estimation of analog data. Digital recordings are made with ones and zeros, while analog recordings are made with linear bumps and dips. While digital information is not as exact as analog information, it can be used with other digital devices, such as computers, making editing and reproduction of the information easier and faster. Because digital media is more compatible and does not degrade over time, it has become the common choice for today's audio and video formats.