4 - Systems Approach to Designing

• A system diagram is often designed using a system block diagram that clearly lays out the input, process and output.
• Examples of inputs:

  • Light Dependent Resistor: Detects changes in light levels (more light = less resistance) [street and security lights]
  • Pressure sensor: Detects changes in pressure of gases or liquids [warning lights]
  • Switch: Switches a circuit on or off [control panels, power switches]
  • Temperature sensor: Detects a change in temperature [household appliances an vehicles]
• Examples of processors:

  • Resistor: Used to limit the flow of current and protects components from overloading
  • Microcontroller: Programmable component is a chip [washing machines]
• Examples of outputs:

  • Buzzer: Gives a sound output [doorbells and toys]
  • Light Emitting Diode: Low power light [power indicators and lamps]
  • Lamp: Uses electricity to produce light [household lighting]
  • Speaker: Translates electrical signal into audible sound [sound systems, laptops, radios]
• An open loop system is one which does not make decisions on its own or loop back to a previous part of the program.
• A closed loop system contains a decision and feedback arrow that can lead back to a previous stage in the process.
• A microcontroller is a tiny computer on a single chip with a processor core, designed to implement a specific function and are found in remote controls, appliances, toys, etc.
• Microcontrollers are programmed for decision making with counting and timing functions

  • Timers for processes with a time-controlled output
  • Counters for storing number of times an event has occured