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Electrical Safety

• Work safely
      Prevent accidents
      Hot Components
      Risk Assessments
      Portable Appliance Testing
• Dangers of electricity
      First Aid
      Electric Shocks
      Burns
      Emergency Help
      Capacitors - Retain Lethal Charge
• Circuit breakers and fuses
      thermal
      fuse
      magnetic
      calculations
• Wire a three-pin mains plug
• Transformers
      Safe low voltage
      Isolated from the mains

Systems and Subsystems

• Systems
      built from one or more subsystems
      Input
      Process
      Output
      Arrows represents information flows

Flow Charts

• Flow Chart Symbols
      START, INPUT, PROCESS, OUTPUT
      DECISION - Yes / No Answers,
      LOOP, END
      Construct and interpret flowcharts

Transducers and Signals

• Transducers
      Input
      Output
• Signals
      current or voltage represents information
• Noise
      an unwanted signal
      reducing noise
• Processes
      counting
      timing
      amplifying
      logic
      memory
• Analogue and Digital
      ADC and DAC

Analogue Systems

• many input devices produce analogue signals
• audio systems
       audio amplifiers
       analogue input
       analogue output

Digital Systems

• logic gates
• flip-flops
• counters
• timers

Combinational Logic

• Combinational Logic
      LOW = 0
      HIGH = 1
• Gates
      AND, OR, NOT, NAND and NOR
• Truth Tables
      up to four gates
      up to three inputs
      convert a written description into gates

Sequential Logic

• 4013 - D-type flip-flop
      data latch
      frequency divider - timing diagrams
• 4017 - counters
      timing diagrams

555 Timers

• The 555 Chip
• Astable      T = (R1+2R2)C / 1.44
• Monostable      T = 1.1 R x C

Analogue Signals

• processors
      analogue
      digital
      converters D to A, A to D
• signals
      analogue
      digital
• analogue
       Audio amplifiers
• Operational Amplifiers
      Comparator
          One-bit A to D converter
      voltage gain (Gv) = Vout / Vin
      power bandwidth
• Op Amp Properties
      very large input resistance
      low output resistance
      very large voltage gain
      saturates at the supply voltages

Basic Electronics

• The Basics
      Voltage, Volts (V)
      Current, Amps (A)
      Resistance, Ohms (Ω)
      Power, Watts (W)
      P = IV        Power = Current x Voltage
      Sum circuit voltages
      Voltage across parallel components
      Current in series circuits
      Current sum at a junction
      Current flows, only if there is a PD.
      Frequency, Hertz, (Hz)
      Capacitance, Farads, (F).
• Ohms Law
      R = V / I
• Resistors and Calculations
      up to four series resistors
      up two parallel resistors
      Voltage dividers
      Pull up and pull down
• Sine waves
      voltage-time graph
      current-time graph
      peak value
      period value
      frequency = 1 / time period
      RMS calculations
      V_peak = 1.4 x V_rms
      V_rms = 0.7 x V_peak

Passive Components

• Components
      power ratings
      current ratings
      voltage ratings
      tolerance
      polarity
      selecting suitable components
• Resistors
      colour code
      BS1852
      E24
• Capacitors
      Markings
      Polarisation
   
    

Switches

• reed switch
• microswitch
• toggle switch
• tilt switch

Diodes

• Diodes
      conduct in one direction only
      forward voltage drop = 0.7 V
      forward-bias
      reverse-bias
• Power Supply Rectifiers
      half-wave
      full-wave
      bridge
• Back EMF Diodes
      connected across a relay coil or motor
      protect the semiconductor
• LED
      calculate series resistor
• LDR
      has a very high resistance in the dark
      resistance decreases when light level increases
• Thermistor
      ntc type
      resistance decreases if temperature increases

Active Components

• NPN bipolar transistor
      emitter, collector, base
      bipolar transistor switch / driver
      base resistor needed
• N Channel MOSFET
      gate, drain and source
      MOSFET switch / driver
      MOSFET no gate resistor needed
• Compare MOSFET and Bipolar Transistor

Audio Entertainment Systems

• Audio Systems
      Tuner
      Amplifier
      Microphone
      Loudspeakers
      MP3 Player
      CD and DVD players
      CD and DVD recorders

Radio Systems

• The Simple Radio
      Block Diagram
      Aerial
      RF tuned circuit
      Demodulator
      AF amplifier
      Loudspeaker

Radio Signal Modulation

• Radio Signals and Modulation
      Carrier
      Information Signal
      Amplitude Modulation (AM)
      Frequency Modulation (FM)
      Compare FM and AM
• Simple Radio Receiver
      Sensitivity -ability to receive weak signals
      Selectivity -select the wanted frequency - reject others