Basic Electronics Review B. Furman 27JAN2015
Dec 14, 2015
Lecture Flow Today Items to focus on this week
Lab 1 PortMaster build HW 1 and Questionnaire due Thursday Term Project overview + video of past projects
Finish basic electronics review: Voltage divider Impedance of a capacitor
Learning Objectives Get prepared for Lab 1 and started on PortMaster build Get started on the term project Explain in simple terms what is meant by:
Voltage Current Ground Resistor, Capacitor, Inductor Impedance Power
Determine equivalent series and parallel impedances Explain the significance of a voltage divider Derive an expression for the impedance of a capacitor
Mechatronics Concept Map
System toControl
Sensor
SignalConditioning
Controller(Hardware & Software)
PowerInterface
Actuator
UserInterface
PowerSource
BJ Furman 22JAN11
ME 106ME 154ME 157ME 195
ME 120ME 297A
ME 106ME 120
ME 106ME 190ME 187
ME 110ME 136ME 154ME 157
ME 182ME 189ME 195
ME 106ME 120
ME 106
INTEGRATION
Key Concepts
Voltage Ground Current Resistor Capacitor Inductor Impedance Power
Take out a sheet of paper Explain the concepts in
terms that a 6th grader could understand
First, work on your own, then, introduce yourself to someone you have NOT met yet, and share your answers.
Basic Electronics Review - 1 Voltage – put it in terms that a 6th grader could understand
“Pressure” Pressure on electric charge (e-). Units are in Volts Urges charge to ‘flow’ Measured relative to a reference pressure level
An “across” quantity – we measure it across two points (Don’t say ‘the voltage through…’)
R1
R2
R3
Vi
+
A B
C
D
“High” pressure
“Low” pressure
Voltage source acts like a pump
Ground is often taken as the low pressure point, but any point could be taken as ‘ground’
ex. VAD = Vi = -VDA
Basic Electronics Review - 2
Current – put it in terms that a 6th grader could understand “Flow”
Flow of electric charge (e-). Units are in Amps The response of charge to applied voltage Need a complete circuit for current to flow
A “through” quantity – we measure it through an element
R1
R2
R3
Vi
+
A B
C
D
“High” pressure
“Low” pressure
We will assume ‘conventional’ current flow – positive charges flow out of the + terminal and return to the - terminal
I
Basic Electronics Review - 3 Resistor – put it in terms that a 6th grader could understand
“Flow restriction” (causes a pressure (voltage) drop across it), an impedance
Drinking a milkshake through a straw Small diameter straw – high resistance
Causes large pressure drop Large diameter straw – low resistance
Causes small pressure drop Units are in Ohms Dissipates power in heat! R1
R2
R3
Vi
+
A B
C
D
“High” pressure
“Low” pressure
Basic Electronics Review - 4 Ohm’s Law (know it cold!)
V=I*R A relationship between current and voltage for a resistor
The slope of the V-I line The voltage drop across a resistor is proportional to the current
through it
V,volts
I, Amps
R R increasing
V
I R
Basic Electronics Review - 6
Power (units are in Watts)P = I2R = (V/R)2R = V2/RP = I2R = I2(V/I) = IV
Note: can calculate thepower required for anycircuit by measuring I andV and taking their product
R1
R2
R3
Vi
+
A B
C
D
Any circuit
I
Capacitor Capacitor– put it in terms that a 6th grader could
understand “Accumulator”, water tank
Pressure storage. Stores energy in an electric field Voltage across the leads takes time to build up. Units of capacitance
are Farads
+ -
2
2
1
1
CVE
idtC
V
dt
dVCi
dt
dQ
CVQ
V
)2cos(2)2sin((
)2sin()sin(
ftfCAdt
ftAdC
dt
dVCi
ftAtAV
Inductor Inductor – put it in terms that a 6th grader could
understand “Flywheel, merry-go-round”
An inertia. Stores energy in a magnetic field Tries to oppose changes in current flow. Units of inductance are
Henrys
+ -
i
2
2
1
1
LiE
VdtL
i
dt
diLV
V
)2cos(2)2sin((
)2sin()sin(
ftfLAdt
ftAdL
dt
diLV
ftAtAi
The Voltage Divider Consider two resistances in series What is VA in terms of
Vi, R1 and R2Vi
+
A
D
R2
R1
VA
So what? Why is this important?
Voltage divider effect occurs whenever one circuit is connected to another
Voltage dividers can be used to set a voltage level somewhere between a given supply voltage and ground If significant current is desired, it is better to use a power supply
or voltage regulator