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 shock
THE 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
voltagecurrentresistance
Voltage tester
voltage levelrugged construction
Clip-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 the
largest 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
Voltage
Current
Resistance
Power
R1
R2

R3

Total
8.psd

24 V

4

Infinite

(open)

24 V

0

Infinite


0

0

0

0

0

0
Voltage
Current

Resistance

Power
R1
R2

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


10 mA

10 mA

10 mA
Voltage
Current
Resistance
Power
R1
R2

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
Voltage
Current
Resistance
Power
R1
R2

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

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Pre Basic Electronics Ppt