Systems and approach to Design

• Inputs


  Input devices allow systems to understand changes in the environment around them.
• Examples of Inputs


  Light-dependent resistor (LDR) that senses light levels for street lamps to know when it is dark.Thermistors detect when it is too hot or cold in a room.
• Switches


  Switches allow current to flow through them when the contacts inside are joined together. They are usually named after how they work. 
• Examples of Switches

  Push to make - push button to turn on circuit

  Push to break - push button to stop circuit
• Uses of switches

  PTM/PTB switch - Console controller buttons

  Magnetic switch - Window sensors on alarms

  Toggle switch - Power switches

  Rocker switch - Light switches

  Tilt switch - To detect if something is no longer level
• Sensors


  Sensors can be used to detect changes in light level, temperature and pressure. They are used in a wide range of products, from night lights to security alarms and central heating systems.
• Microcontrollers


  Microcontrollers provide functionality and give intelligence to products and systems. From mobile phones to washing machines, many everyday products are controlled by these devices.
• process devices


  Process devices take the signal from the input stage of a system and act on it by changing it in some way 
• Microcontrollers come in different sizes with varying numbers of pins for the connection of input and output devices - for example, 8 pin, 14 pin and 18 pin. A peripheral interface controller (PIC) is an example of a microcontroller that is widely used.
• Advantages of using microcontrollers


  The size of a circuit can be significantly reduced. This is because programming replaces physical components.

  They can be reprogrammed many times. This allows changes to be made without replacing actual components.

  They have pins connecting several input and output devices, adding flexibility.
• Disadvantages of using microcontrollers


  They cost more than traditional integrated circuits. They are therefore not always the best option for simple systems.

  Programming software and hardware is required. This can be expensive to buy.

  The coding language of the system must be learned and this adds to training costs.
• In order for microcontrollers to work correctly they must be programmed. This can be achieved using a wide range of software, hardware and different programming languages.
• Microcontrollers can be programmed using a range of different methods. These include:

  • text-based programming languages, such as BASIC, C++ and Python
  • block-based programming editors
  • flowchart software (Scratch.io)
• Light outputs

  • when current flows through the filament it heats up and light is produced
  • filament lamps are increasingly being replaced with energy-saving alternatives, such as light-emitting diodes (LEDs)
• Buzzer Outputs

  • buzzers have an oscillator inside a plastic case
  • when current flows through them they produce a buzzing sound, often around 400 Hertz (Hz) in frequency depending on the type of buzzer used
  • examples of their use include in doorbells and alarms
• Speakers Outputs

  • speakers produce sound using electromagnetism
  • they usually require a driver circuit to provide a signal that they can use, such as an audio amplifier
  • the correct speaker resistance value must always be used to prevent damage to the driver circuit