Transcript Chapter 8
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 • • • • • 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)