Elec

• Electronic systems

  Designed to process electrical signals
• Input sensing units

  • Convert non-electrical input signals to an electrical form
• Output devices

  • Convert the processed electrical signal into another form (e.g. light, sound, motion)
• Input sensing units

  • Switch unit
  • Light sensing unit
  • Moisture sensor
  • Temperature sensor
  • Reed/magnetic switch
  • Pressure sensor
  • Sound sensor
• Processing units

  Take an electrical input and produce a modified electrical output (e.g. amplified or inverted)
• Processing units

  • Digital
  • Analogue
  • Pulse generator
• Sub-systems

  Building blocks that make up a complete system, each performing a definite function within the main system
• Sub-systems

  • Sensors in road
  • Reed/magnetic switch
  • Pulse generator
• Delay, latch and comparator

  • Useful processing devices to delay a signal, provide basic memory, convert analogue signals to digital signals
• Delay unit

  Provides a time delay, the output signal goes high for a preset time period
• Latch unit (positive)


  When the input signal goes high the output signal goes high and stays high until it is reset
• Comparator unit

  Compares the input signal with a reference voltage, if the input is larger the output is high, if the input is smaller the output is low
• Drivers

  Provide additional current to drive outputs like motors and lamps
• Types of drivers

  • MOSFET driver for high power loads like a motor or solenoid
  • Transistor switch driver for low power loads like a buzzer, lamp or LED
• Analogue signal

  Can have any value between the supply voltage, changes gradually
• Digital signal

  Can only have one of two values, 0/1 or high/low, changes instantly
• Logic gates

  • Digital processing units, decision making units within electronic systems
• Main logic gates

  • AND gate
  • OR gate
  • NOT gate (inverter)
• Inverter

  Reverses the digital input signal, the output goes low when the input goes high and vice versa
• OR gate

  The output signal goes high when either one or the other or both the input signals go high
• AND gate

  The output signal goes high only when both the input signals go high
• Steps for successful system design

  1. Decide upon input units required

  2. Decide upon output units required

  3. Decide what processing units are required

  4. Draw a block diagram of the system

  5. Set up the system and try it out

  6. Make changes if required and draw a final block diagram
• Output units

  • Lamp unit
  • LED unit
  • Buzzer unit
  • Motor unit
  • Solenoid unit
• Lamp unit

  Converts an electrical signal into light
• LED unit


  Converts an electrical signal into light
• Buzzer unit


  Converts an electrical signal into sound
• Motor unit

  Converts an electrical signal into rotational motion
• Solenoid unit

  Converts an electrical signal into linear motion
• Electronic circuits consist of components, e.g. lamps, batteries connected by wires
• Electric current


  The flow of electrons through a material
• Current flows from the positive terminal to the negative terminal of the battery
• Current


  Measured in A, mA or μA
• Current is not used up in an electrical circuit. Whatever current leaves the battery must return to the battery
• Series circuit


  • The current is the same at all points in the circuit
• Parallel circuit


  • The current splits at the junction of three or more wires. The sum of currents entering a junction is always equal to the sum of currents leaving a junction
• Voltage

  The force that drives current around a circuit
• Voltage

  Measured in V, mV or μV
• Voltage is used up in any electrical circuit
• Series circuit


  • The sum of voltages around the circuit is equal to the voltage of the battery
• Parallel circuit


  • The voltage is the same across all components in parallel