Digital Systems

Lesson Objectives YOU SHOULD BE ABLE TO: Explain the difference between electronics and electricity Define and give examples of analog and digital signals. Explain the difference between analog and digital signals. Explain why digital signals are a better means of transmitting information. Next Generation Science Standards: MS-PS4-3. Integrate qualitative scientific and technical information to support the claim that digitized signals are a more reliable way to encode and transmit information than analog signals. [Clarification Statement: Emphasis is on a basic understanding that waves can be used for communication purposes. Examples could include using fiber optic cable to transmit light pulses, radio wave pulses in wifi devices, and conversion of stored binary patterns to make sound or text on a computer screen.] [Assessment Boundary: Assessment does not include binary counting. Assessment does not include the specific mechanism of any given device.] PS4.C: Information Technologies and Instrumentation  Digitized signals (sent as wave pulses) are a more reliable way to encode and transmit information. (MS-PS4-3) Do Now: Write these down on your handout!!!

Electricity vs. Electronics – using electrons to transfer energy Electronics – using electrical signals to convert, process and transfer information Any circuit that is powered, that has electrons in motion, is an example of electricity; if the main purpose of the circuit, or some part of a circuit, is to convey information then the circuit, or that part, is an example of electronics.

Information is All Around Us Music, Images, Email, Vine/Video, Texts, Tweets, Movies, TV, Games, CDs, Vinyl Records,… How much of it is… Analog??? Digital???

Analog Processes What do these items have in common? Continuous signal. Has infinite resolution (theoretically). The signal is inherently noisy. Continuous – without interruption

Analog Signals We live in an ANALOG world – things can be louder or quieter, hotter or colder, longer or shorter, on a “sliding scale”. If we record sound onto a vinyl record, we’re putting an analog signal onto the vinyl.

Analog Signals Analog signals can take on an infinite range of values We live in an ANALOG world – An ANALOG SIGNAL is a continuous signal which represents physical measurements Analog signals can take on an infinite range of values

Analog Signals Other than music, can you name 5 other analog signal sources? Examples: Temperature, Light intensity, Color, Force, Time There are many, many more… Remind students that analog signals should be: 1) continuous, 2) have infinite resolution, 3) and usually are somewhat noisy.

Digital Processes What do these items have in common? Discrete bands of analog signal. Easier to get a device to switch into a number of known states. No noise. Discrete – individually separate and distinct

Digital Signals We live in an ANALOG world, but we make it DIGITAL – Sample rate Take music for example…when an artist plays or sings a song, we hear the song in ANALOG: the notes seem to ring in your ear rather than just appear and disappear instantly. There is a continuous feel to a note and the possibility for it to range infinitely high or low. But that’s not what you hear from a CD player or your IPod. For the most part, what we listen to today is analog music recorded and played in a DIGITAL format! The song is sampled, i.e. we measure the amplitude of the sounds, and convert that into a set of 1’s and 0’s.

Digital Signals We live in an ANALOG world, but we make it DIGITAL – A DIGITAL SIGNAL is a discrete representation of a physical signal; digital signals have a finite set of possible values. The number of values in the set can be anywhere between 2 and a-very-large-number-that’s-not-infinity. Why is the lower limit for DIGITAL 2? Well, the simplest digital representation is ON and OFF, two values. Usually we represent those two states with a LOW voltage (0 volts) or a HIGH voltage (usually 5 V or 3.3 V depending upon the transistor technology). 0110,1000,…

Digital Signals We live in an ANALOG world, but we make it DIGITAL – Digital signals (i.e., 100011010111) can be sent long distances w/o degrading the signal They can be compressed, so more information can fit in the same sized “shoe box” Why is the lower limit for DIGITAL 2? Well, the simplest digital representation is ON and OFF, two values. Usually we represent those two states with a LOW voltage (0 volts) or a HIGH voltage (usually 5 V or 3.3 V depending upon the transistor technology). 0110,1000,…