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Digital Technology

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Slideshow on the IB topic Digital Technology

Slideshow on the IB topic Digital Technology

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  • 1. Digital technology
    Contents:
    Base 2 and base 10 number system
    Bits and bytes
    PN diodes
    Boolean logic
    Logic gates
    Digital and analog basics
    Storing devices for digital
    Changing Analog to digital
    How cds store in 1 and 0
    What are CCDs?
    Image capturing
    Sampling for analog to digital conversion
    Work cited pages
  • 2. What are binary digits?
    Computers use binary numbers, and therefore use binary digits in place of decimal digits. The word bit is a shortening of the words "Binary digIT." Whereas decimal digits have 10 possible values ranging from 0 to 9, bits have only two possible values: 0 and 1.
  • 3. Decimal and binary numbers.
    You can see that in binary numbers, each bit holds the value of increasing powers of 2. That makes counting in binary pretty easy
    E.g 1011 means
    1 * 23) + (0 * 22) + (1 * 21) + (1 * 20) = 8 + 0 + 2 + 1 = 11
    Some more examples
    10 = 101011 = 101112 = 110013 = 110114 = 111015 = 111116 = 10000
  • 4. Bits and bytes.
    Bits are rarely seen alone in computers. They are almost always bundled together into 8-bit collections, and these collections are called bytes.
    With 8 bits in a byte, you can represent 256 values ranging from 0 to 255, as shown here:
    0 = 000000001 = 000000012 = 00000010...254 = 11111110255 = 11111111
  • 5. Bits and bytes continued
    CD uses 2 bytes, or 16 bits, per sample. That gives each sample a range from 0 to 65,535, like this:
    0 = 00000000000000001 = 00000000000000012 = 0000000000000010...65534 = 111111111111111065535 = 1111111111111111
  • 6. Analog at a glance
    As a technology, analog is the process of taking an audio or video signal (in most cases, the human voice) and translating it into electronic pulses. Digital on the other hand is breaking the signal into a binary format where the audio or video data is represented by a series of "1"s and "0"s.
  • 7. A to D
    Digital technology breaks your voice (or television) signal into binary code—a series of 1s and 0s—transfers it to the other end where another device (phone, modem or TV) takes all the numbers and reassembles them into the original signal. The beauty of digital is that it knows what it should be when it reaches the end of the transmission.
  • 8. Is the duplication perfect?
    But like any tansferred technology, digital has a few shortcomings. Since devices are constantly translating, coding, and reassembling your voice, you won't get the same rich sound quality as you do with analog.
  • 9. Can we use the digital phone using an analog line?
    There are digital-to-analog adapters that not only let you use analog equipment in a digital environment, but also safeguard against frying the internal circuitry of your phone, fax, modem, or laptop. Some adapters manufactured by Konexx come designed to work with one specific piece of office equipment: phone, modem, laptop, or teleconferencer. Simply connect the adapter in between your digital line and your analog device.
  • 10. Comparing Analog Vs. Digital
    http://telecom.hellodirect.com/docs/Tutorials/AnalogVsDigital.1.051501.asp
    Visit the above site for more details of Analog Vs. Digital
  • 11. Ancient way of recording the analog way
    In the Beginning: Etching Tin
    Thomas Edison is credited with creating the first device for recording and playing back sounds in 1877. His approach used a very simple mechanism to store an analog wave mechanically. In Edison's original phonograph, a diaphragm directly controlled a needle, and the needle scratched an analog signal onto a tinfoil cylinder . (see the clip in the link below)
    http://communication.howstuffworks.com/analog-digital1.htm
  • 12. An analog wave
    Image from www.howstuffworks.com
    Analog Wave
    What is it that the needle in Edison's phonograph is scratching onto the tin cylinder? It is an analog wave representing the vibrations created by your voice. For example, here is a graph showing the analog wave created by saying the word "hello":
  • 13. Analog recording contd….
    The waveform was recorded electronically rather than on tinfoil, but the principle is the same. What this graph is showing is, essentially, the position of the microphone's diaphragm (Y axis) over time (X axis). The vibrations are very quick -- the diaphragm is vibrating on the order of 1,000 oscillations per second. This is the sort of wave scratched onto the tinfoil in Edison's device. Notice that the waveform for the word "hello" is fairly complex.
  • 14. Getting in to the digital world
    In a CD (and any other digital recording technology), the goal is to create a recording with very high fidelity (very high similarity between the original signal and the reproduced signal) and perfect reproduction (the recording sounds the same every single time you play it no matter how many times you play it). To accomplish these two goals, digital recording converts the analog wave into a stream of numbers and records the numbers instead of the wave. The conversion is done by a device called an analog-to-digital converter (ADC). To play back the music, the stream of numbers is converted back to an analog wave by a digital-to-analog converter (DAC). The analog wave produced by the DAC is amplified and fed to the speakers to produce the sound.
  • 15. Converting an analog wave to digital wave
    http://communication.howstuffworks.com/analog-digital3.htm
    Here is a typical wave (assume here that each tick on the horizontal axis represents one-thousandth of a second):
  • 16. ……………..contd…
    When you sample the wave with an analog-to-digital converter, you have control over two variables:
    The sampling rate - Controls how many samples are taken per second
    The sampling precision - Controls how many different gradations (quantization levels) are possible when taking the sample
  • 17. Convert the curve to numbers
    In the following figure, let's assume that the sampling rate is 1,000 per second and the precision is 10:
    The green rectangles represent samples. Every one-thousandth of a second, the ADC looks at the wave and picks the closest number between 0 and 9. The number chosen is shown along the bottom of the figure. These numbers are a digital representation of the original wave. Want to know the digital form of this curve? 7 8 9 5 3 4 0 3 7 5
    Binary form? For individual digit
    7 8 9 and so on
    111 1000 1001 …………..
  • 18. When the DAC recreates the wave from these numbers, you get the blue line shown in the following figure:
    You can see that the blue line lost quite a bit of the detail originally found in the red line, and that means the fidelity of the reproduced wave is not very good. This is the sampling error. You reduce sampling error by increasing both the sampling rate and the precision
  • 19. In the following figure, both the rate and the precision have been improved by a factor of 2 (20 gradations at a rate of 2,000 samples per second) and then 4000 samples/sec.:
  • 20. CDs and DVDs.
    http://electronics.howstuffworks.com/cd.htm
    Exploring Sound: Digital Sound
    Laser discs such as CDs and DVDs carry digital information, which is represented by the binary code -- combinations of 1s and 0s. Any number can be represented in binary code. Learn how this information is encoded in the clip in the above link
  • 21. CD’s and DVD’s
    Data is stored digitally
    A series of ones and zeros read by laser light reflected from the disk
    Strong reflections correspond to constructive interference
    These reflections are chosen to represent zeros
    Weak reflections correspond to destructive interference
    These reflections are chosen to represent ones
  • 22. CD’s and Thin Film Interference
    A CD has multiple tracks
    The tracks consist of a sequence of pits of varying length formed in a reflecting information layer
    The laser beam shines on a metallic layer through a clear plastic coating
  • 23. A CD’s pits and bumps
    www.physics.byu.edu/faculty/rees/106/PPT/Class26.ppt
  • 24. Reading a CD
    As the disk rotates, the laser reflects off the sequence of bumps and lower areas into a photodector
    The photodector converts the fluctuating reflected light intensity into an electrical string of zeros and ones
    The pit depth is made equal to one-quarter of the wavelength of the light
    www.physics.byu.edu/faculty/rees/106/PPT/Class26.ppt
  • 25. Reading a CD
    When the laser beam hits a rising or falling bump edge, part of the beam reflects from the top of the bump and part from the lower adjacent area
    Light reflecting from the top and bottom of the pit is a half-wavelength out of phase, so the intensity drops.
    www.physics.byu.edu/faculty/rees/106/PPT/Class26.ppt
  • 26. Reading a CD
    The bump edges are read as ones
    The flat bump tops and intervening flat plains are read as zeros
  • 27. DVD’s
    DVD’s use shorter wavelength lasers
    The track separation, pit depth and minimum pit length are all smaller
    Therefore, the DVD can store about 30 times more information than a CD
  • 28. In the case of CD sound, fidelity (the similarity between the original wave and the DAC's output ) is an important goal, so the sampling rate is 44,100 samples per second and the number of gradations is 65,536. At this level, the output of the DAC so closely matches the original waveform that the sound is essentially "perfect" to most human ears .
  • 29. Why is a CD’s capacity approximately 750 mb?
    One thing about the CD's sampling rate and precision is that it produces a lot of data. On a CD, the digital numbers produced by the ADC are stored as bytes, and it takes 2 bytes to represent 65,536 gradations. There are two sound streams being recorded (one for each of the speakers on a stereo system). A CD can store up to 74 minutes of music, so the total amount of digital data that must be stored on a CD is:
    44,100 samples/(channel*second) * 2 bytes/sample * 2 channels * 74 minutes * 60 seconds/minute = 783,216,000 bytes (Convert to kbs and then Mbs.)
  • 30. What is a digital image?
    Essentially, a digital image is just a long string of 1s and 0s that represent all the tiny colored dots -- or pixels -- that collectively make up the image. If you want to get a picture into this form, you have two options:
    You can take a photograph using a conventional film camera, process the film chemically, print it onto photographic paper and then use a digital scanner to sample the print (record the pattern of light as a series of pixel values).
    You can directly sample the original light that bounces off your subject, immediately breaking that light pattern down into a series of pixel values -- in other words, you can use a digital camera
  • 31. Capturing image
    The image sensor employed by most digital cameras is a charge coupled device (CCD). Some cameras use complementary metal oxide semiconductor (CMOS) technology instead. Both CCD and CMOS image sensors convert light into electrons.
    A simplified way to think about these sensors is to think of a 2-D array of thousands or millions of tiny solar cells.
    A CMOS sensor
  • 32. Digitisation of the light
    http://www.olympusmicro.com/primer/digitalimaging/concepts/concepts.html
    http://electronics.howstuffworks.com/digital-camera1.htm
    The above site has a video clip to explain the digitisation of the light .
  • 33. Digital Camera Resolution
    The amount of detail that the camera can capture is called the resolution, and it is measured in pixels. The more pixels a camera has, the more detail it can capture and the larger pictures can be without becoming blurry or "grainy."
    Photo courtesy MorguefileThe size of an image taken at different resolutions
  • 34. Capturing Color
    Unfortunately, each photosite is colorblind. It only keeps track of the total intensity of the light that strikes its surface. In order to get a full color image, most sensors use filtering to look at the light in its three primary colors. Once the camera records all three colors, it combines them to create the full spectrum
    For illustrations and explanations visit: http://electronics.howstuffworks.com/digital-camera3.htm
  • 35. Work cited pages
    Complete binary mathematics.
    http://www.binarymath.info/
    convert binary numbers to decimals
    http://www.bellaonline.com/articles/art48652.asp
    Basic principles of magnetic recording using digital data in HDD.
    http://www.usbyte.com/common/HDD.htm#top
    storage types
    http://www.jegsworks.com/Lessons/lesson6/lesson6-2.htm
    Details of DVDs.
    http://electronics.howstuffworks.com/dvd3.htm
    Optical recording in a CD.
    http://physicsworld.com/cws/article/print/1383/1/world-11-10-7-2
    Detailed study of dvds and cds comparison. More emphasis on technology of data capture.
    http://www.iti.uni-stuttgart.de/~ghermanv/Lehre/Seminar/material/Presentation4/talk.pdf
    For complete know how on CCDs and image capture in a digital camera
    www.howstuffworks.com