BBC Microbit

Learning Objectives

Lesson 1  ( Sensors, Transducers and Actuators )

  • Understand the terms Sensor, Actuator and Transducer
  • Use the BBC Micro Bit temperature sensor to display the temperature

Lesson 2  ( Manual Auto Open Closed Good and Bad )

  • Student can explain why we need them and explain the advantages and disadvantages of control systems
  • Student can explain the difference between a manual and and an automatic control system
  • Student can explain with examples  the difference between an Open and  Closed Control Systems

Explanation Temperature Room Control - Manual Automatic

Manual Control System

Automatic Control System

Is Option A an Open or Closed control system ?

Is Option B an Open or Closed control system?

Open Loop Control System

Give Some Practical Examples of Open Loop Control System

Advantages of Open Loop Control System

Disadvantages of Open Loop Control System

CLOSED Loop Control System

Control system in which the output has an effect on the input quantity in such a manner that the input quantity will adjust itself based on the output generated is called closed loop control system. Open loop control system can be converted in to closed loop control system by providing a feedback. This feedback automatically makes the suitable changes in the output due to external disturbance. In this way closed loop control system is called automatic control system. Figure below shows the block diagram of closed loop control system in which feedback is taken from output and fed in to input.

Practical Examples of Closed Loop Control System

Advantages of Closed Loop Control System

Disadvantages of Closed Loop Control System

Feedback Loop of Control System



Transducers

Sensors

Actuators

Transducers

A Transducer is any device that converts one form of energy to another form

  • Microphone converts sound to electrical impulses and a loudspeaker converts electric impulses to sound 
  • Solar cell converts light into electricity
  • A thermocouple converts heat into electric
  • An incandescent light converts electric energy to light energy
  • An electric motor is a transducer for conversion of electricity into mechanical energy or motion
  • Understand the terms Sensor, Actuator and Transducer
  • Use the BBC Micro Bit temperature sensor to display the temperature

Sensors

A sensor is a device that received and responds to a signal.

  • Photocell
  • Thermometer
  • Pressure Sensor

Actuator

A device that actuates or moves something. Am Actuator is a specific type of transducer

Do BBC Micro Bit Activities

1 Code the micro bit pins to control switching and LED on and Off

2 Code the micro bit to use the temperature sensor.  - display HOT if temp > 27  Else  Display COLD ( take it outside to compare the outside and inside temperature ( hook up battery pack) )

3 Set up the micro bit light sensor to measure light and switch on and off the LED at a preset Light levels ( programmed )

4 Rock Scissors paper Complete this activity Click Here


Lesson 3  ( Distributed vs Central Systems )

  • Student can discuss the social and ethical impacts of embedded systems
  • Student can explain the difference between a centrally controlled system with a distributed system ( and outline advantages and disadvantages )

Central

Distributed

Centralized System 

Characteristics of Centralized System ​

Example –
Wikipedia. Consider a massive server to which we send our requests and the server responds with the article that we requested. Suppose we enter the search term ‘junk food’ in the Wikipedia search bar. This search term is sent as a request to the Wikipedia servers (mostly located in Virginia, U.S.A) which then responds back with the articles based on relevance. In this situation, we are the client node, wikipedia servers are central server.

  • One single central unit: One single central unit which serves/coordinates all the other nodes in the system.
  • Dependent failure of components: Central node failure causes entire system to fail. This makes sense because when the server is down, no other entity is there to send/receive response/requests.

Advantages of central system:

Disadvantages of central system:


Distributed systems

In Distributed systems, every node makes its own decision. The final behaviour of the system is the aggregate of the decisions of the individual nodes. Note that there is no single entity that receives and responds to the request.

Example –
Google search system. Each request is worked upon by hundreds of computers which crawl the web and return the relevant results. To the user, the Google appears to be one system, but it actually is multiple computers working together to accomplish one single task (return the results to the search query)

Advantages of Distributed System

  • Distributed systems are very stable and a single failure doesn’t do much harm compared to central system.
  • Scalability  - Easier to scale Vertical and Horizontal

Disadvantages of Distributed System

  • Distributed systems are the most difficult to maintain as many possible points of failure.

Choose any electronic control systems and prepare a 10 minute presentation - Some Examples Below 

I will post this on classroom : Mention all the key terms Sensor, Transducer, Actuator, Controller/Processor Reference Point .... 

  • 1
    Bio metric access control systems
  • 2
    Home Control System
  • 3
    Elevator control system
  • 4
    Flood control System
  • 5
    Air pollution control system
  • 6
    Gate control system
  • 7
    Washing Machine Control System
  • 8
    keypad access control system

Lesson 4  ( Analog  Digital Data Text Compression )

  • distinguish between analog and digital data
  • Understand why we use the binary system to represent data
  • List and describe 3 ways that text can be compressed.

What is the difference between data and information

Data Basic values or facts. Information Data that has been organized or processed in a useful manner

Multimedia Devices

What Types of media do Multimedia Devices Handle

Analog Digital Data

Data can be represented in one of two ways: analog or digital. Analog data is a continuous representation, analogous to the actual information it represents. Digital data is a discrete representation, breaking the information up into separate elements.

                   Analog Digital

Analog Data

A continuous representation of data

Digital Data

A discrete representation of data

A mercury thermometer is an analog device. The mercury rises in a continuous flow in the tube in direct proportion to the temperature. We calibrate and mark the tube so that we can read the current temperature, usually as an integer such as 75 degrees Fahrenheit. However, the mercury in such a thermometer is actually rising in a continuous manner between degrees. At some point in time, the temperature is actually 74.568 degrees Fahrenheit, and the mercury is accurately indicating that, even if our markings are not detailed enough to note such small changes.

mercury thermometer

Why do we use Binary to represent data in a computer ?

  • 1
    Less Expensive
  • 2
    More Reliable

Degradation of analog and digital signals

Representing Numeric Data

If positive integers it is simply  a mapping from one number system to another.

Representing Text

A text document can be decomposed into paragraphs, sentences, words, and ultimately individual characters. To represent a text document in digital form, we simply need to be able to represent every possible character that may appear. The document is the continuous (analog) entity, and the separate characters are the discrete (digital) elements that we need to represent and store in computer memory

At this point, we should distinguish between the basic idea of representing text and the more involved concept of word processing. When we create a document in a word processing program such as Microsoft® Word, we can specify all kinds of formatting: fonts, margins, tabs, color, and so on. Many word processors also let us add art, equations, and other elements. This extra information is stored along with the rest of the text so that the document can be displayed and printed the way you want it. The core issue, however, is the way we represent the characters themselves; therefore, those techniques remain our focus at this point.

The ASCII ( American Standard Code for Information Interchange) (7/8) bits per char

The Unicode Character Set ( the encoding uses 16 bits per character )

For consistency, Unicode was designed to be a super set of ASCII. That is, the first 256 characters in the Unicode character set correspond exactly to the extended ASCII character set, including the codes used to represent them. Therefore, programs that assume ASCII values are unaffected even if the underlying system embraces the Unicode approach.


Text Compression

  • 1
    Keyword encoding
  • 2
    Run-length encoding
  • 3
    Huffman encoding

Keyword Encoding

Keyword Encoding

Replacing a frequently used word with a single character

Run-length Encoding

Replacing a long series of a repeated character with a count of the repetition

Huffman encoding

Using a variable-length binary string to represent a character so that frequently used characters have short codes

Keyword Encoding


Try Encoding ? What is the Compression Ratio ?

The human body is composed of many independent systems, such as the circulatory system, the respiratory system, and the reproductive system. Not only must all systems work independently, but they must interact and cooperate as well. Overall health is a function of the well-being of separate systems, as well as how these separate systems work in concert

Run-length Encoding


AAAAAAA

flag character, followed by the repeated character, followed by a single digit  *A7

Huffman encoding


Then the word “DOORBELL” would be encoded in binary as 1011110110111101001100100

If we had used fixed length string (8 Bits ) how many bits to represent ?

Decoding Hoffman Coding

An important characteristic of any Huffman encoding is that no bit string used to represent a character is the prefix of any other bit string used to represent a character. Therefore, as we scan from left to right across a bit string, when we find a string that corresponds to a character, that must be the character it represents. It can’t be part of a larger bit string

So how is a particular set of Huffman codes created?

Beyond scope of IB