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Lecture 1
ECE 92
Projects in Electrical and Computer
Engineering
Saturday, March 21, 2015
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Basic Concepts
Voltage
V
• Defined as
the amount
of potential
energy in a
circuit.
Current
I
Resistance
R
• The rate of
charge flow
in a circuit.
• Units: Amperes
(A)
• Units: Volts (V)
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Current
High Current
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Low Current
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Voltage
Water
Tower
V
Water
Tower
V
More Energy == Higher Voltage
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Less Energy == Lower Voltage
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Resistance
Water
Tower
Water
Tower
V
V
Big Pipe == Lower Resistance
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Small Pipe == Higher Resistance
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Example
10mA
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Rx
Find Rx and the
power delivered to
the resistor.
100V
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Example
Node – any point where 2 or more circuit elements are
connected together
Wires usually have negligible resistance
Each node has one voltage (w.r.t. ground)
Branch – a circuit element between two nodes
Loop – a collection of branches that form a closed path
returning to the same node without going through any
other nodes or branches twice
How many nodes, branches & loops?
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Kirchoff’s Voltage Law (KVL)
• The algebraic sum of voltages around each loop is zero
 Beginning with one node, add voltages across each branch in
the loop (if you encounter a + sign first) and subtract voltages (if
you encounter a – sign first)
• Σ voltage drops - Σ voltage rises = 0
• Or Σ voltage drops = Σ voltage rises
10Ω
10Ω
30 V
10Ω
10Ω
5Ω
10Ω
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Out
What is the current
through the load
resistor using KVL?
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Kirchoff’s Current Law (KCL)
• The algebraic sum of currents entering a node is zero
 Add each branch current entering the node and subtract each
branch current leaving the node
• Σ currents in - Σ currents out = 0
• Or Σ currents in = Σ currents out
10Ω
10Ω
30 V
10Ω
10Ω
5Ω
Out
What is the current
through the load
resistor using KCL?
10Ω
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Equivalent Resistance
Parallel Resistors:
R2
R1
1
1 1
1
   ... 
REQ R1 R 2
RN
RN
Series Resistors:
R1
R2
REQ  R1  R2  ...  RN
RN
REQ
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Example
px
100V
2kΩ
1.5kΩ
3kΩ
ix
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1kΩ
1kΩ
vx
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Use circuit reduction to
find vx, ix, and px.
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Thévenin and Norton Equivalent
Circuit
R
Is
Vs
Norton Circuit
Thévenin Circuit
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R
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Summary of two-terminal equivalent
circuits
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Example
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Capacitors
•
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Equivalent Capacitors
Parallel Capacitors:
C2
C1
CEQ  C1  C 2  ...  CN
CN
Series Capacitors:
C1
C2
1
1
1
1
 
 ... 
CEQ C1 C 2
CN
CN
CEQ
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Inductors
•
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Equivalent Inductors
Parallel Inductors:
L1
L2
1
1 1
1
   ... 
LEQ L1 L2
LN
LN
Series Inductors:
L1
L2
LEQ  L1  L2  ...  LN
LN
LEQ
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Example
R
L
VAu(t)
C
VA=10V
R=1kΩ
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Vc(t)
C=0.5μF
L=2H
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Arduino Uno
USB
Analog Reference
Pin
Test LED
(pin 13)
Digital Pins
Toggles External
Power and USB
Power
On LED
Reset Button
External Power
Supply In (9-12V)
Digital
Ground
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Analog In Pins
0-5V
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The Arduino IDE
Check
Syntax
Upload
Code
Runs when
reset pushed
Runs when
setup() done
and loops
infinitely
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Console
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Useful Functions for the Arduino
pinMode(pin, INPUT/OUTPUT);
ex: pinMode(13, OUTPUT);
digitalWrite(pin, HIGH/LOW);
ex: digitalWrite(13, HIGH);
delay(time_ms);
ex: delay(2500); // delay of 2.5 sec.
// NOTE: -> commands are CASE-sensitive
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Make an LED blink
-
+
- +
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Examples of Arduino Code
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Components that you will be using
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Shields
Datalogging Shield
Wifi Shield
Touchscreen Shield
Wave Shield
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Project Ideas
• http://playground.arduino.cc/
• http://www.ucsbieee.org/ECE%20199%20Spring%202012.html
• http://www.ucsbieee.org/ECE%20199%20Spring%202014.html
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