Electronic systems and components

• What is an Input device

  a device that allows systems to understand changes in the environment around them
• Examples of input devices

  light dependent resistor

  push-to-make switch (mouse)

  thermistor
• What is a process device

  devices that take the signal from the input stage of a system and act on it by changing it on some way
• Examples of Process subsystems

  intergrated circuit

  microcontroller
• What is a Microcontroller


  A miniaturised computer programmmed to perform a specific task and embedded in a product
• Digital sensor


  detects a yes/no situation or on/off situation
• Analogue


  a sensor that measures how big a physical quanitity is
• Light dependent resistor


  A LDR is an analogue sensor used to sense light

  its resistance falls as light level increases

  Used in street lamps, night lights and digital clocks
• Thermistor


  An analogue sensor used to sense temperature

  Two types of thermistor:

  -negative temperature coefficient

  -positve temperature coefficient

  Used in ovens , room thermostats,electrical heaters
• What does an output subsystem do?

  an output subsystem converts an electrical signal into a desired function
• Examples of output devices

  Buzzer

  light emitting diode
• buzzer


  a resistor that produces a sound ouptut

  buzzers are useful for providing feedback that a user has pressed a button

  used in burgular alarms,dishwashers and kitchen timers
• light emitting diode


  produces a light ouput

  they are available in a range of colours,sizes and shapes and can be used as a indicator

  a resistor must be used with an led to limit current flowing or the LED will burn out
• Feedback in systems


  Feedback in a system is when a signal from the output is taken and fed back into the input of the process subsystem.
• What does feedback allow microcontrollers to do

  to monitor the effect of the changes it makes to it output devices in order to achieve precise control over a system
• Give an example of a feedback

  electirc oven control system
• Advantages of 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 for connecting several input and output devices, adding to flexibility.
• Disadvantages of Microcontrollers

  • They often 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 language of the system must be learned and this adds to training costs.
• Differences between a Microprocessor and Microcontroller

  -Microcontroller is designed for specific tasks whereas a microprocessor is designed for general purpose applications

  -Microprocessor is at the centre of a computing system whereas a microcontroller is at the centre of a embedded system

  -Microprocessors funcitions at high speeds whereas a microcontroller functions at low speeds
• Explain how a light dependent resistor works

  LDRs are used to detect light levels in the street. Their resistance decreases as the light intensity increases. In the dark and at low light levels, the resistance of an LDR is high, and little current can flow through it. In bright light, the resistance of an LDR is low and more current can flow through it.Turning on the street light.