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Chapter 8
Designing Electronic
Systems
Electronic Systems
• Inputs
• Sensors (convert physical phenomenon into
electrical signals)
• Signals – electricity that contains information
• Processes
• Timing, switching, comparing, and amplifying
• Outputs
• Transducers – loudspeakers, buzzers and lights
• Actuators – motors and solenoids
• Displays – lamps and monitors
Terms
• Electricity – the movement of electrons.
• Direct Current (DC) – electricity that flows in
one direction.
• Batteries & Photovoltaic cells
• Alternating Current (AC) – electricity that
changes direction of flow.
• Household wiring, generators
• Potential Difference
• Conductors – Easily carry electrons
• Insulators – poor to no carry of electrons
Flow of Electrons
• Voltage (volts “V”)– the pressure that drives
electrons.
• Current (Amps “A”) – the quantity of
electrons that flow in a circuit.
• Resistance (Ohms “R” or “”) – the
opposition to the flow of electrons.
Ohm’s Law
• 1 volt of pressure through 1 ohm of
resistance results in 1 Ampere of current.
• V=IxR
• I=V/R
• R=V/I
V = Voltage in Volts
I = Current in Amps
R = Resistance in Ohms
Sensors
• Provide the link between the physical world
and the electronic world.
•Light
•Heat
•Magnetism
•Humidity
•Strain
•Acceleration
•Position
•Motion
Properties of Sensors
• Light
• Photovoltaic Cells, Photresistor and
Light Dependant Resistor (LDR).
• Heat
• Thermocouple, Thermistor
• Sound
• Crystal microphone, Dynamic microphone.
• Position
• Switch, potentiometer – linear or rotary
Systems Outputs
• Displays – provide information
• Light bulb, meter, LED, 7-segment, solenoid
• Actuators – make movements
• Motor, steppers, electromagnet, relay, solenoid
• Transducers – convert electrical signal into
a physical property
• Speaker, horn, buzzer, heater
Displays
• LED – Light Emitting Diode – 20 mA max.
• Seven-Segment Diplays – Common anode
and common cathode.
Anode (+)
Cathode (-)
Actuators
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DC Motors
Stepper Motors
Solenoids
Relay
Electromagnets
System Processors
• Integrated Circuits (IC) – Many transistors
on one chip
• Transistor-Transistor Logic (TTL) IC – operate
on 5 volts not sensitive to static electricity.
• Complementary Metal Oxide Semiconductor
(CMOS) – operate between 4.5 an 16 volts, use
little current, but are susceptible to static
electricity.
555 Timer Chip
• CMOS IC logic
• Monostable operation – returns to its
original state after a certain time.
• Adjustable by capacitor/resistor combination.
• Astable Operation – constantly pulsing from
state to state.
• Frequency (Hz) – how often the pulses occur.
More Circuits
• Counting
• Switching
• Transistors – semiconductor devices that can
switch large currents on and off by using a
small control current.
Other Terms
• Capacitor
• Concepts
• Frequency (Hz)