Pre Basic Electronics Ppt
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Transcript of Pre Basic Electronics Ppt
-
Pre-Basic Electronics
Lesson
ES 104
-
Laboratory Safety Measures
Work only in clean dry areas.Do not wear loose or flapping clothing.Wear only nonconductive shoes.Remove all rings, wristwatches, bracelets, ID chains and tags, and similar metal items.Do not use bare hands to remove hot parts.Use a shorting stick to remove high voltage charges on capacitors.Make certain that the equipment being used is properly grounded.If more than 50V are to be used in the work, at least two other people must be present in the lab, including an instructor.Always wire a circuit completely before connecting it to the power source. -
Laboratory Safety Measures
Review the wiring to avoid damage to components due to accidentally misplacing the wire in the circuit. Provide a switch within easy access with which the circuit can be de-energized.Turning off a power supply while the circuit is still connected to it can damage components as current and/or voltage spikes can occur as the supply turns off. Remove and replace fuses only after the power to the circuit has been de-energized.Make sure all equipment is properly grounded.Use extreme caution when removing or installing batteries containing acid.In case of an electrical fire, de-energize the circuit and report it immediately to the appropriate authority. -
HIGH VOLTAGE SAFETY PRECAUTIONS
Consider the result of each act.Keep away from live circuits.Do not work alone.Do not tamper with interlocks.Do not ground yourself.Never energize equipment in the presence of water leakage. -
First Aid For Electrical Shock
Turn power OFF & remove victim from electric contact. Do Not touch victim until power is removed.Apply artificial respiration if not breathing. Keep victim warm.Keep victim head low so blood can flow to brain. Avoid placing victim where breathing obstruction may occur.Cold water or ice pack for first degree and minor second degree.Dont break blisters ! For open blistersno water or cold packsuse thick clean bandages to avoid infection.Do not remove charred clothing ..let a medical pro do it.. -
Body Resistance & Shock
Dry skin resistance: 100,000 to 600,000 OhmsWet skin resistance: 1,000 OhmsInternal body.hand to foot: 400 to 600 OhmsEar to ear: about 100 OhmsBurns and neurological damage are the most common injuries caused by electrical shockTHE DANGER OF HARMFUL SHOCK INCREASES
AS THE VOLTAGE INCREASE
VOLTAGES AS LOW AS 30V Can Be Dangerous !!
-
Note: Symbols in red are most usedknow them
Metric and Prefix Notations
Number
Prefix
Symbol
10 1
deka-
da
10 2
hecto-
h
10 3
kilo-
k
10 6
mega-
M
10 9
giga-
G
10 12
tera-
T
10 15
peta-
P
10 18
exa-
E
10 21
zeta-
Z
10 24
yotta-
Y
Number
Prefix
Symbol
10 -1
deci-
d
10 -2
centi-
c
10 -3
milli-
m
10 -6
micro-
(greek mu)
10 -9
nano-
n
10 -12
pico-
p
10 -15
femto-
f
10 -18
atto-
a
10 -21
zepto-
z
10 -24
yocto-
y
-
Multimeter
voltagecurrentresistanceVoltage tester
voltage levelrugged constructionClip-on ammeter
measures current
without direct
connection
Digital circuit probe
measures digital
logic levels
Oscilloscope
used to measure
and examine
voltage waveforms
Instruments
-
GENERIC CIRCUIT
Electron
current
flow
Control
Device
Power
Source
Load
Device
Conductor
Protective
Device
1.psd -
CURRENT MEASUREMENT
Connected in Series
Circuit Schematic
AMMETER
2.psd3.psd -
VOLTMETER
VOLTMETER
- Connected in parallel
to measure battery
voltage.
- Connected in parallel
to measure lamp voltage.
VOLTAGE MEASUREMENT
-
RESISTANCE MEASUREMENT
Measured with
an Ohmmeter
(multimeter used
as an ohmmeter)
Ohmmeters should never
be connected to live circuits!
5.psd -
Meter Safety
Never use an ohmmeter on a live circuitNever connect an ammeter in parallel with a voltage sourceUse proper range settings: Do NOT overload a meterDo not short terminals using meter probesNever measure unknown high voltages: find out the range before attaching a meterCheck for frayed or broken meter leadsAvoid touching exposed meter probesIf possible, connect meter before applying power to circuitWhen connecting a meter to a live circuit work with one hand at your side to lessen the danger of shockTo reduce the danger of accidental shock, disconnect meter test leads immediately after completing a measurement -
Series Circuit
Same current through each componentSum of voltage drops = supply voltage (Kirchoff Voltage Law)Largest resistance has thelargest voltage drop.
Add resistanceLowers currentOne open the circuit fails.The total resistance is the sum of all resistors:RT = R1 + R2 + R3
I
IT
6.psd -
Sample Series Circuit 1
20 k
3 mA
12 V
6 V
42 V
180 mW
36 mW
18 mW
126 mW
60 V
4 k
2 k
14 k
3 mA
3 mA
3 mA
VoltageCurrent
ResistancePower
R1R2
R3
Total
8.psd -
24 V
4
Infinite
(open)
24 V
0
Infinite
Sample Series Circuit 2
0
0
0
0
0
0
VoltageCurrent
Resistance
Power
R1R2
Total
10.psd -
60 V
4 k
2 k
0 (Short)
6 k
10 mA
40 V
20 V
0
600 mW
200 mW
400 mW
0 mW
Sample Series Circuit 3
10 mA
10 mA
10 mA
VoltageCurrent
ResistancePower
R1R2
R3
Total
12.psd -
Troubleshooting
Series CircuitOpen:No currentSource voltage at the openRest are zerosShortCurrent IncreaseV is zero at the short -
Parallel Circuit
Same Voltage across all componentsSmallest resistance, most current.Add a branch:Increase CurrentDecrease Overall ResistanceOne branch opens, current is smaller than normal.Resistance of Network is less than smallest resistor -
Parallel Resistor Network
From Kirchoffs Current Law: IT = I1 + I2 + I3 + ------ + IN
From Ohms Law: I = V/R and R = V/I
IT
=
VT
R1
+
VT
R2
+
VT
R3
+
----
+
VT
RN
=
1
R1
+
1
R2
+
1
R3
+
----
+
RN
1
VT
RT = VT / IT
=
1
R1
+
1
R2
+
1
R3
+
----
+
RN
1
1
R1
I1
R2
I2
R3
I3
RN
IN
VT
IT
-
1.5 A
1 A
3 A
8
4.36
132 W
72 W
36 W
24 W
Sample Parallel Circuit
24 V
24 V
24 V
24 V
16
24
5.5 A
VoltageCurrent
ResistancePower
R1R2
R3
Total
15.psd -
EFFECT OF A SHORT CIRCUIT
ACROSS PARALLEL BRANCHES
Breaker
opens
Circuit
breaker
closed
Switch
open
Switch
closed
Current
jumps to
max value
Voltage
drops
-
Troubleshooting
ParallelShort: Fuse blowsOpen: Less current -
KIRCHHOFFS VOLTAGE LAW
VT = V1 + V2 +V3
VT - V1 - V2- V3 = 0
+24V - 4V - 8V - 12V = 0
V1 = 4V
V2 = 8V
V3 = 12V
VT = 24V
19.psd -
KIRCHHOFFS CURRENT LAW
IT = I1 + I2 + I3
IIN = IOUT
IT
(22A)
I1
(12A)
I2
(6A)
I3
(4A)
(6A)
(4A)
(10A)
20.psd -
Various resistors types
-
When measuring resistance, remove
component from the circuit.
-
Resistor Color Code
-
DC vs. AC
-
CYCLE
One complete wave of alternating current or voltage
21.psd -
SOLVING EXAMPLE
Vpeak = Vrms x 1.414
Vpeak = (120 V) (1.414)
Vpeak = 170 V
Vp-p = Vpeak x 2
Vp-p = (170 V) x (2)
Vp-p = 340 V
22.psd -
FREQUENCY
The number of cycles produced per second
Frequency =
Period
1
F =
T
1
=
0.25 s
1
= 4 Hz
23.psd -
Common Circuit Symbols
www.spacetec.org
Full Wave
Rectifier
Operational
Amplifier
Opto
Coupler
Transformer
Iron Core
Light-
Emitting
Diode(LED)
Electrolytic
Capacitor
Potentiometer
Normally
Open
Pushbutton
Switch
Normally
Closed
Pushbutton
Switch
Transformer
Air Gap
NPN
Transistor
PNP
Transistor
Darlington
PNP
Transistor
Alternating
Current
Source
Relay
Current
Controlled
Switch
Zener
Diode
Voltage
Controlled
Switch
Diode
Battery
Fuse
Triode
Quartz
Crystal
Resistor
Variable
Inductor
Inductor
Variable
Capacitor
Ground
Lamp
Single Pole
Single Throw
Normally Open
24.unknown25.unknown26.unknown27.unknown28.unknown29.unknown -
IDEAL TRANSFORMER
Power in = Power out
V x I primary = V x I secondary
(120 V) (0.625 A) = (15 V) x (5 A)
75 VA = 75 VA
The basis for
transformer operation is
mutual inductance
54.psd -
EXAMPLE 31-2
VS = 2 x 120 V = 240 V
Turns ratio =
= 1:2
NP
NS
=
50
100
55.psd -
EXAMPLE 31-3
Turns ratio =
=
= 20:1
240 V
20
VS =
= 12 V
NS
NP
100
5
56.psd -
EXAMPLE 31-4
60 V
25
= 2.4 A
IP = 5 x IS
= 5 x 2.4 A
= 12 A
IS =
=
VS
RL
57.psd -
Circuit Protection
FusesCircuit breakersOverloadThermal shunt -
OVERLOADED CIRCUIT
Branch circuit
rating:
15 A / 120 V
1500 W
Total power = 2640 W
Total current = 22 A
360 W
120 V
3 A
120 W
120 V
1 A
1440 W
120 V
12 A
120 W
120 V
1 A
600 W
120 V
5 A
58.psd -
FUSES
Ferrule-contact
cartridge fuse
Knife-blade
cartridge fuse
Glass cartridge fuse
Plug fuse
Fuse symbol
OR
-
CIRCUIT BREAKERS
Circuit breaker
symbol
Light
duty
Heavy
duty
High-voltage
-
CURRENT
RATINGS
Plastic automotive
fuse
Household
circuit breaker
20
Rated current
15
Rated
current
-
USING AN OHMMETER TO
TEST FUSES
Good
0
Zero resistance reading
71.psd -
TYPES OF CONTACTS
Single-pole, double-throw
(SPDT)
Double-pole, single-throw
(DPST)
Double-pole, double-throw
(DPDT)
73.psd74.psd75.psd -
AWG WIRE SIZES
The larger the gauge number the smaller
the actual diameter of the conductor.
The primary cable selection criteria are
current rating and allowable voltage drop
76.psd77.psd -
Capacitor
Battery
Capacitor
Unit = Farad
Pico Farad - pF = 10-12F
Micro Farad - uF = 10-6F
is used to store charge for a short amount of time
-
Capacitor
-
Prototyping Board/ Breadboard
Example of how components are
Inserted in the protoboard
Voltage
Current
Resistance
Power
R
1
R
2
R
3
Total
Voltage
Current
Resistance
Power
R
1
R
2
Total
Voltage
Current
Resistance
Power
R
1
R
2
R
3
Total
R
1
I
1
R
2
I
2
R
3
I
3
R
N
I
N
V
T
I
T
J4
Key = Space
U2
TRIODE_VIRTUAL
K1
RELAY1A
C2
0.047F
T2
IRON_CORE_XFORMER
IN+
IN-
VS-
VS+
OUT
U3
OPAMP_5T_VIRTUAL
S2
Key = Space
X2
100V_100W
LED_blue
LED1
Q5
FZT705
Q3
2N3906
Q1
2N2222A
1
2
4
3
D3
1B4B42
D1
1BH62
FUSE
S1
1
1mH
U1
OPTOCOUPLER_VIRTUAL
V3
1V 1000Hz 0Deg
V2
12V
C3
Key = a
100pF
50%
50%
Key = a
100K_LIN
R2
Key = Space
J3
J2
1V 0V
D2
02BZ2.2
J1
1mA 0mA
T1
NLT_VIRTUAL
.
.
L2
Key = a
100mH
50%
R5
1kohm
X1
CRYSTAL_VIRTUAL