Transcript Behavior-Based Robotics

EE 1106: Introduction to EE
Freshman Practicum
Lab - Lecture:
Maximum Power Transfer
Nonlinear Circuit Elements
Photovoltaic Effect
Dan O. Popa, Intro to EE, Spring 2015
Thevenin and Norton Equivalents
Dan O. Popa, Intro to EE, Spring 2015
Norton Equivalent
RTh
a
a
=
VTh
IN
RTh
b
VTh  RTh I N
Dan O. Popa, Intro to EE, Spring 2015
b
VTh
IN 
RTh
Maximum Power Transfer
Maximum power transfer when Rs=RL
(Impedance matching)
Dan O. Popa, Intro to EE, Spring 2015
Intellectual Themes of EE
• Modularity (ex: device)
– Resistor, Capacitor, Inductor, Transistor, Diode, OpAmp
• Abstraction (ex. circuit)
– Signal, System, Circuit, Block diagrams, Data
flow diagrams (state machines), signal flow
graphs
• Modeling (ex: linear)
– KVL, KCL equations
Dan O. Popa, Intro to EE, Spring 2015
Linear Systems have the Superposition
Property
• Fundamental Property of Linear Circuits
• Replace all but one source in the circuit with a
short (voltage source) or an open (current
sources).
• Apply analysis to find nodal voltages.
• Repeat for all sources
• Add all nodal voltages to find the total result.
Dan O. Popa, Intro to EE, Spring 2015
RLC Circuit as a Linear System
R
u
u
1
u
u
2
C
u(t)
RLC
q(t)
3
L
Kirchoff’s Voltage Law (KVL):
Dan O. Popa, Intro to EE, Spring 2015
i(t)
Nonlinear Circuit Elements- Diode
Semiconductors (Si, Ge) can be
doped with impurities
Dan O. Popa, Intro to EE, Spring 2015
Image Sources: Internet
Nonlinear Circuit Elements- Diode
Dan O. Popa, Intro to EE, Spring 2015
Image Sources: Internet
Nonlinear Circuit Elements- Transistor
Dan O. Popa, Intro to EE, Spring 2015
Image Sources: Textbook
Transistor use: Digital Inverter
Dan O. Popa, Intro to EE, Spring 2015
Image Sources: Textbook
Solar cells - PN Junction using PV effect
• Sunlight strikes the cell, photons with energy above
the semiconductor bandgap impart enough energy to
create electron-hole pairs.
A typical silicon PV cell is composed of
a thin wafer consisting of an ultra-thin
layer of phosphorus-doped (N-type)
silicon on top of a thicker layer of borondoped (P-type) silicon.
• This separation induces a fixed electric current and
voltage in the device. The electricity is collected and
transported by metallic contacts on the top and bottom
surfaces of the cell.
When sunlight strikes the surface of a
PV cell, this electrical field provides
momentum and direction to lightstimulated electrons, resulting in a flow
of current when the solar cell is
connected to an electrical load
Dan O. Popa, Intro to EE, Spring 2015
Source: MIT Solar Decathlon
Solar cells – material and efficiency
•silicon (Si),
•gallium arsenide
(GaAs),
•cadmium
telluride (CdTe),
•copper indium
diselenide (CIS),
•hydrogenated
amorphous
silicon.
Dan O. Popa, Intro to EE, Spring 2015
Source: MIT Solar Decathlon
PV Cells, Modules, Arrays
In the case of a single-junction device, the
efficiency of the solar cell, the ratio of the
power produced, and the incident light
power are limited.
Photons with energies below the bandgap of
the material produce only heat. Excess
energy above that needed to generate
electron-hole pairs also produces heat.
Power – [W]
Efficiency= Electrical Power/Sun Power
Power density – W/m2 – Irradiance (Flux)
Energy – Wh
Photovoltaic cells are connected electrically in series and/or parallel
circuits to produce higher voltages, currents and power levels.
Photovoltaic modules consist of PV cell circuits sealed in an
environmentally protective laminate, and are the fundamental
building block of PV systems.
Photovoltaic panels include one or more PV modules assembled
as a pre-wired, field-installable unit. A photovoltaic array is the
complete power-generating unit, consisting of any number of PV
modules and panels.
Dan O. Popa, Intro to EE, Spring 2015
Source: MIT Solar Decathlon
PV Power
Sun Power – [W]
Power density – W/m2
– Irradiance (Flux)
Image Sources: http://www.nrel.gov/gis/solar.html, Wikipedia
Dan O. Popa, Intro to EE, Spring 2015
PV Systems
Subsystems:
DC-AC power inverter,
battery bank,
system and battery controller,
auxiliary energy sources
specified electrical load (appliances).
Direct Coupled PV System
Dan O. Popa, Intro to EE, Spring 2015
Source: MIT Solar Decathlon
Next Time: Dynamical Circuits
(RC, RL, RLC)
Dan O. Popa, Intro to EE, Spring 2015
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