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ELEC4

Programmable Control Systems

Generalised Control System

• Control System Diagrams
       Input
       Error Detector
       Instructions
       Processor
       Driver
       Output Device
       Feedback Sensor
       Open Loop Control Systems
       Closed loop Control Systems
• Feedback
      Negative
      Positive
• Compare Hardwired and Software Controlled Systems

Microprocessor Architecture

• microprocessors and microcontrollers
       clock
       memory (ROM and RAM)
       input/output ports
       bus structure
       social and economic benefits

Flow Charts

• Flow Chart Box Shapes
       Sequence
       Start / End
       Input / Output
       Process
       Decision ( yes / no answer )
       Loop

Microcontroller programs

• subroutines to
       configure the input and output pins
       read data from a sensor
       write data to an output device
       produce a time delay
       produce control signals
       arithmetic and logic
       detect events using polling
       detect events using hardware interrupts
       compare interrupts with polling
• Assembly Code
        interpret programs

Input subsystems

• 8-bit digital ramp ADC
       operation
       uses
       limitations
• Flash ADC
       operation
       calculate component values
       compare flash ADCs with digital ramp
• Reflective and Slotted Optical Switches
       binary coded shaft encoder
       Gray code advantages

Output subsystems

• 8-bit Summing DAConverter
       operation
       uses
       calculate component values
       output voltage calculation
• Multiplexed Seven Segment Displays
       LCD
       LED
• Multiplexed Dot Matrix Displays
• Stepper Motor
       properties
       compare with conventional
• Conventional Motors
       properties
       compare with stepper
• Interfacing Subsystems
       Tri-State Buffers
       Data Latches - D-type flip-flops
• Inverting Schmitt Triggers
       operation
       calculate switching levels
       regenerate a noisy input signal
• Drives for Multiplexed Displays
       LCD and
       LED and LED Matrix
• H-Bridge Driver
       use and
       operation
• Drivers for
       conventional motors
       stepper motors

Robotic Systems

• Sensors
• Actuators
• Control Architectures
• Power Sources
• Algorithms to achieve an objective
• Artificially Intelligent Behaviour
       Artificial Neural Networks
• Applications
• Social and Economic Impact
• Possible Future Developments

ELEC5

Communications Systems

General Principles

• transfer of meaningful information from one location to another
• Draw a block diagram
       input transducer
       carrier generator
       modulator/encoder
       transmitter
       transmission link (medium)
       receiver
       demodulator/decoder
       output transducer

Media

• electromagnetic signals
       twisted pair
       coaxial cable
       optical fibre
       free space

Bandwidth

• bandwidth, the capacity to carry information

Signals, Noise and Distortion

• noise
• distortion
• crosstalk
• signal-to-noise ratio (in dB)

Audio Systems and Filters

• Reactance
       of a capacitor using the formula Xc = 1 / ( 2 π f C )
• RC Passive Filters
       high pass
       low pa ss
       calculate the breakpoint frequency
• First Order Active Filters
       inverting op-amp circuits
       treble cut
       treble boost
       bass cut
       bass boost
       calculate the breakpoint frequency
       calculate components for a given breakpoint frequency

Audio Power Amplifiers

• Power Amplifiers IC s

Radio Communication

• Carrier Wave
• Media - see above
• Amplitude Modulation
       draw time waveforms and the envelope shape
            for different information signal amplitudes
            for different information signal frequencies
       modulation depth
       bandwidth = 2 F_max
       labelled spectrum diagrams
            sidebands / side frequencies
            sine wave information signal
            multiple frequency information signal like music
• Frequency Modulation
       draw time waveforms
            for different information signal amplitudes
            for different information signal frequencies
       deviation
       bandwidth = 2 ( Deviation + F_max )

Frequency Bands

• LF and MF bands use AM
       channel allocation within LF and MF broadcasting
• VHF band entertainment broadcasting uses FM
       88 MHz – 108 MHz
       relationship between channel spacing and signal bandwidth
• VHF band is used for DAB broadcasting
       217.5 MHz – 230 MHz
       Multiplexes on different frequencies
       Data rates depend of the programme content

Antennas

• Length of a half-wave dipole
• c = F λ
• Antenna Impedance = Feeder Cable Impedance
       ( at the design frequency )

LC Tuned Circuits

• Tuned Circuits
• Resonance
• At resonance, the inductor reactance = the capacitor reactance
  At resonance X_L = X_C
• Voltage and Current in L and C near Resonance
• f = 1 / ( 2 π √(LC))
• sketch a resonance curve
• Q Factor
• resonance curves for lower and higher Q Factors
• Higher Q provides better selectivity in a radio receiver.

Simple Radio Receiver

• The Simple Radio
       aerial
       tuned circuit
       detector/demodulator
       earphone

Superhet Radio Receiver

• Supersonic Heterodyne Receiver
       Block Diagram for a superhet receiver consisting of
            Aerial
            RF amplifier improves sensitivity
            Local Oscillator
            Mixer
            IF Amplifier and Filter
            Demodulator
            AGC
            AF Amplifier
            Loudspeaker
       Principle of Operation
       Frequency spectrum at the output of the mixer
            mixer products
            sum and difference frequencies
       Advantages
       Disadvantages

Digital Communication

• Compare analogue and digital
• Digital Pulse Modulation
       PAM - Amplitude
       PWM - Width
       PPM - Position
       PCM - Code
• Digitising
       Sampling Rate
       Resolution
       Bit Rate
       Calculations
• Duplex
       half
       full
• Signalling
       Serial Data
       Parallel Data
       Synchronous
       Asynchronous
       Start Bit
       Stop Bit
       Parity Bit
       Baud Rate
• Parallel to Serial and Serial to Parallel Data Conversion
       shift registers
       draw timing diagrams

Packet Switched Networks

• Packet Switched Networks

Multiplexing

• Carry a number of signals on one transmission medium
       frequency division
       time division
       space division (non AQA idea)
• Action of a multiplexer
• Multiplexers for serial data transmission
• 2 to 1multiplexers
       circuit diagram
       explanation
• 4 to 1 multiplexers
•      circuit diagram
       explanation
• A Schmitt trigger can be used to regenerate a digital signal

Mobile Communications

• mobile telephones
       connect to the telephone network via a radio link
       base station
       few frequencies but lots of phones
       calculate the maximum number of mobile telephones that can be      supported on one cell given the size of the cell and the available      bandwidth
       repeater
       regenerator
       cellular
       frequency reuse
       mobile communications in everyday life

Optelectronics

• Optical Fibres
       optical digital signals
       how optical fibres are constructed
       how they work
       total internal reflection
       attenuation
       dispersion
       radiation
       laser diode light source
       PIN diodes detectors