Electronics by hokokwah

ELECTRONICS SUMMARY

ELECTRONICS Electronics Materials and Components •Conductors, Insulators and Semiconductors •Wire Rating •Power Supplies •Tools •Common Electronic components.

Circuits • Potential Divider • Darlington Pairs • Moisture Sensing Circuit • Light Sensing Circuit • Temperature Sensing Circuit • Time Delay Circuit • Decade Counter • 7-Segment Display Driver

Electronic Calculation • SI units for Electrical Measurement • Ohm’s Law • Electrical Power • Resistance calculation

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MATERIALS Conductors, Insulators and Semi-conductors There are three types of materials used in electronic components: 1. Electrical conductors are materials that allow electricity to flow through them easily => Low resistivity values. 2.Electrical insulators are materials that prevent electrical flow. => High resistivity values. 3. Semi-Conductors are materials that exhibit both conducting and insulating properties. The way in which the material is connected to a power supply determines whether it will conduct an current or prevent it from flowing. Eg diode.

MATERIALS CONDUCTORS

Copper Aluminium Brass Steel All other metals

INSULATORS

Plastics Rubber Wood Ceramic

SEMICONDUCTORS

Silicon Germanium

MATERIALS Wire Rating Single core wire is rigid, but can be bent to shape easily. Multi-stranded wire is flexible and suitable for portable usage. The lowest number of strands is 7: one in the middle, 6 surrounding it. The next level up is 19, 37 and 49 are common, then in the 70 to 100 range. Application for Multi-Stranded wire 1. Do not need to move, used 7 strands. 2. Required to move around, 19 is the lowest that should be used and 49 is much better. 3. Constant repeated movement, such as assembly robots, and headphone wires, 70 to 100 is recommended.

POWER SUPPLIES 1.

D.C Supply — Dry Cell Batteries + +

AAA 1.5V

AA 1.5V

+ C 1.5V

D 1.5V

A.C Supply — socket 220– 240V (Local)

PP3 9V

Electric Main

TOOLS TOOL

DIAGRAM

TOOL

Soldering Iron To solder the leads of electronic parts to the tracks of an electronic circuit board.

Multimeter To measure voltage, current or resistance.

Wire Cutter To cut wires and leads.

Wire Stripper To remove plastic insulation from wires.

Long Nose Pliers To use for twisting and bending wires.

De-soldering Tool To remove solder from a soldered joint.

DIAGRAM

De-soldering tool

INPUT COMPONENTS NAME Slide Switch Use : ON/OFF switch

Rocker Switch Use : light, electrical, electric kettle

DIAGRAM

SYMBOL Double pole double throw

NAME Push Button Switch Use : door bell, calculator

Micro Switch Use : Safety switch for machine

DIAGRAM

SYMBOL

INPUT COMPONENTS NAME

DIAGRAM

SYMBOL

NAME

DIAGRAM

Reed Switch Use : magneticcontrolled security alarm system

Tilt Switch Mercury Use : warning to an excessive angle of tilt

Toggle Switch Use : Control of direction for motor and ON/OFF

Membrane Switch Use : calculator, handphone

SYMBOL

INPUT COMPONENTS NAME

DIAGRAM SYMBOL

NAME

Light Dependent Resistor (LDR) Use : Light Sensor

Thermistor Use :

Microphone Use : Sound Detector

Moisture Sensor Use : detect water

DIAGRAM

SYMBOL

Temperature sensor

No symbol

COMMON COMPONENTS NAME Resistor Use : Restrict or resist the flow of current.

Diode Use : allow current to flow in one direction only

DIAGRAM

SYMBOL

Fixed resistance

NAME

DIAGRAM

SYMBOL

Variable Resistor

C cathode

A anode

Thyristor Used : control in alarm system.

G , gate A , anode

C cathode

COMMON COMPONENTS NAME Capacitor Use : store electrical charge for a period of time.

DIAGRAM

SYMBOL

Ceramic Capacitor

NAME Transistor is an auto switch. It is activate by having a small current flow to the ‘Base’.

Electrolytic Capacitor

DIAGRAM

SYMBOL

NPN Transistor

c collector b base

e emitter

PNP Transistor

c collector b base

e emitter

COMMON COMPONENTS NAME Solenoids To produce movement using a Plunger.

DIAGRAM

SYMBOL

NAME Relay a switch from low voltage circuit to control high voltage circuit.

DIAGRAM

SYMBOL

OUTPUT COMPONENTS NAME

DIAGRAM

SYMBOL

NAME

Light Emitting Diode (LED) Use : give out light, come in different colours.

Lamp or Bulb Use : give out light from filament.

Buzzer Use : give

Piezo Use : give off high pitch sound for alarm system.

off buzzing sound

DIAGRAM

SYMBOL

OUTPUT COMPONENTS NAME

DIAGRAM

SYMBOL

Motor or Stepper Motor Use : To rotate and power by d.c.

Sevensegment LED Use : Display Numerical digit.

NAME Bell Use : Ring when current flow through.

No symbol, normally will used the diagram.

Speaker Use : Amplify the sound or music

DIAGRAM

SYMBOL

CIRCUITS 1. Potential Divider used for dividing up the current, so that a part or parts of a circuit only receive the current they require. Consist of two or more components (usually resistors) arranged in series across a power supply.

Formula

Vout

R2 = Vin R1 + R 2

Input Voltage

Required Output Voltage

CIRCUITS Sensitivity of the circuit can adjusted by replacing the fixed resistor with a variable resistor or potentiometer in the potential divider circuit.

LDR

Variable Resistor

CIRCUITS 2. Darlington Pairs 1) Paired up with a high-gain transistor to a high current transistor . 2) Use for increasing the sensitivity of sensing circuits.

CIRCUITS General Sensing Circuit A typical sensing circuit will consist of 3 main blocks. They are INPUT, PROCESS and OUTPUT. INPUT :This section will consist of potential dividers. Common components used are variable resistor, moisture sensor, light dependent resistor (LDR) and thermistor. PROCESS : This section will consist of either a single transistor or two transistors (Darlington pair). OUTPUT : This section will consist of mainly the output component. Common components used are buzzer, LED, bell, piezo, lamp, bulb, motor, 7-segment LED and speaker.

CIRCUITS INPUT

PROCESS Transistor / Darlington pair

OUTPUT

+ 6V Variable resistor and sensors to be connected at these 2 position. The arrangement will depend on the function of the sensing circuit.

- 0V

Diode D1 protect transistors T1 & T2 from reverse current.

Output Components to be connected at here.

b e Resistor R1 is connected to the base b is to prevent transistor T1 from being damaged by too much current.

c T2 e

CIRCUITS 3. Moisture Sensing Circuit Application : 1) To check the dampness of the soil for a potted plant 2) To raise an alarm when it rains. 3) To alert parents when a baby has wet the bed. 4) To raise the alarm if flooding occurs in a bathroom or kitchen. Block Diagram : INPUT Probes

PROCESS Transistor / Darlington pair

OUTPUT LED / Buzzer

CIRCUITS Moisture Sensing Circuit Circuit Diagram : Dampness Sensing Circuit

Water Sensing Circuit Probes

R2 Small current

Probes

R2 VR1 LED1

LED1 R1

R1 T1

Water

T1 No current

VR1 Water

CIRCUITS

Play

Water Sensing Circuit +9V

Probes

R2 Small current No current

LED1 R1 ON

Water

VR1

CIRCUITS

Play

Water Sensing Circuit +9V

Probes

R2 Small current No current

LED1 R1 ON

Water

VR1

CIRCUITS

Play

Dampness Sensing Circuit +9V

Probes

VR1 Small current No Current

LED1 R1 ON

T1 Water 0V

CIRCUITS

Play

Dampness Sensing Circuit +9V

Probes

VR1 Small current No Current

LED1 R1 ON

T1 Water 0V

CIRCUITS 4. Light Sensing Circuit Application : 1) Lamps that switch on automatically as the light level changes. 2) Digital alarm clock displays that automatically dim at night. 3) Security systems which activate a siren when a light beam is broken. 4) Automatic cameras which adjust the shutter speed according to light levels. Block Diagram : INPUT LDR

PROCESS Transistor / Darlington pair

OUTPUT LAMP

CIRCUITS Light Sensing Circuit Circuit Diagram : Brightness Sensing Circuit

Darkness Sensing Circuit

CIRCUITS

Play

Brightness Sensing Circuit +9V

Very VeryLOW HIGH Resistance Resistance

Small current No current ON

1KΩ

1-10KΩ 0V

CIRCUITS

Play

Brightness Sensing Circuit +9V

Very VeryLOW HIGH Resistance Resistance

Small current No current ON

1KΩ

1-10KΩ 0V

CIRCUITS

Play

Darkness Sensing Circuit +9V

10KΩ Small current No current ON

1KΩ VeryLOW HIGH Very Resistance Resistance

Play

CIRCUITS Darkness Sensing Circuit +9V

10KΩ Small current No current ON

1KΩ VeryLOW HIGH Very Resistance Resistance

CIRCUITS 5. Temperature Sensing Circuit Application : 1) Automatic kettles which switch off at boiling point. 2) Ice alarm to warn of freezing water. 3) Thermosats for air conditioning / heating systems 4) Maintaining a steady oven temperature.

Block Diagram : INPUT Thermistor

PROCESS Transistor / Darlington pair

OUTPUT Motor (Fan/Air-con)

CIRCUITS Temperature Sensing Circuit Circuit Diagram : When Thermistor is working on + t째C.

Cold Sensing Circuit

Heat Sensing Circuit

+ t째C

1K BC108

BC108 BFY51

t째C

BFY51

CIRCUITS

Play

Cold Sensing Circuit +9V Very HIGH LOW Very Resistance Resistance

40Îż C

Small current No current ON

Heater

CIRCUITS

Play

Cold Sensing Circuit +9V Very HIGH LOW Very Resistance Resistance

40Îż C

Small current No current ON

Heater

CIRCUITS

Play

Heat Sensing Circuit +9V

M Small current No current ON

40Îż C Very VeryLOW HIGH Resistance Resistance 0V

Cooler Fan

CIRCUITS

Play

Heat Sensing Circuit +9V

M Small current No current ON

40Îż C Very VeryLOW HIGH Resistance Resistance 0V

Cooler Fan

CIRCUITS 5. Temperature Sensing Circuit Circuit Diagram : When Thermistor is working on - t째C.

Heat Sensing Circuit

Cold Sensing Circuit

+ - t째C

1K BC108

BC108 BFY51

- t째C

BFY51

CIRCUITS 6. Time Delay Circuit Application : 1) Self-timer of a camera, which operates the shutter after a few seconds. 2) Cooking timers which sound a buzzer after a special time. 3) Communal lighting which switches off shortly after the switch is pressed. 4) Screen savers for computer monitors. Block Diagram : INPUT Switch, capacitor & resistor

PROCESS Transistor / Darlington pair / 555 timer

OUTPUT Lamp/ Buzzer / Bell

CIRCUITS Time Delay Circuit Using Capacitor Circuit 1 Switch off a bulb after a time delay.

Circuit 2 Switch on a bulb after a time delay.

CIRCUITS

Play

Time Delay Circuit Using Capacitor

+6V

Circuit 1 Switch off a bulb after a time delay.

Small current No current 1K

Time Delay 1000ÎźF

CIRCUITS

Play

Time Delay Circuit Using Capacitor

+6V

Circuit 1 Switch off a bulb after a time delay.

Small current No current 1K

Time Delay 1000ÎźF

CIRCUITS

Play

Time Delay Circuit Using Capacitor

+6V

Circuit 2 Switch on a bulb after a time delay.

Small current Time Delay

No current 1K

1000ÎźF 0V

CIRCUITS

Play

Time Delay Circuit Using Capacitor

+6V

Circuit 2 Switch on a bulb after a time delay.

Small current Time Delay

No current 1K

1000ÎźF 0V

CIRCUITS Using 555 Timer IC Circuit 1 Switch off a circuit after a time delay.

Circuit 2 Switch on a circuit after a time delay.

CIRCUITS 555 Timer IC

Vcc 4.5-16V

Trigger

Discharge

Output

Threshold

Reset

Control Voltage

CIRCUITS

http://www.bbc.co.uk/schools/gcsebitesize/design/electronics/

CIRCUITS

Play

Circuit 1 Using 555 Timer IC, Switch off a circuit after a time delay. +9V 1M

100ÎźF

4K7 8

555 1

470R

Time Delay

CIRCUITS

Play

Circuit 1 Using 555 Timer IC, Switch off a circuit after a time delay. +9V 1M

100ÎźF

4K7 8

555 1

470R

Time Delay

CIRCUITS

Play

Circuit 2 Using 555 Timer IC, Switch on a circuit after a time delay. +9V 1M

100ÎźF

4K7 8

Time Delay

555 1

4 470R

CIRCUITS

Play

Circuit 2 Using 555 Timer IC, Switch on a circuit after a time delay. +9V 1M

100ÎźF

4K7 8

Time Delay

555 1

4 470R

CIRCUITS 4017 Decade Counter 4017 decade counter is a 16-pin IC that counts up to 10. It has 10 outputs that are switched on one after the other each time the switch is pressed on. The switch can also be replaced by a sensor.

CIRCUITS 4017 Decade Counter

Pins 1 to 7 and Pins 9 to 11 are outputs for the counter. Pin 8 is the Negative (-) power supply, 0V. Pin 12 is the Carry-Out pin (this could be connected to another 4017). Pin 13 is the Enable pin. It can be used STOP the count. Pin 14 is the Clock pin. This will be connected to a manual switch or to an astable 555 timer. Pin 15 is the RESET pin. This returns counter to zero. Pin 16 is the Positive (+) power supply pin. It runs at a voltage between 3V and 16V.

CIRCUITS 4017 Decade Counter used as an electronic dice

CIRCUITS 4026 7-Segment Display Driver The 4026 seven-segment display driver is an IC that is used with seven-segment LED displays to count from 0 to 9. Each time the switch is pressed on, the IC increments the display by 1. The switch can also be replaced with a sensor.

Electronic SI Units Source

Symbol

SI Unit

Symbol

Current

Amperes

Voltage

Volts

Resistance

Ohms

â&#x201E;Ś

Power

Watts

Capacitance

Farads

Electronic Calculation Ohm’s Law Ohm’s Law states that

V R = I

Electrical Power Power = Current x Potential Difference

P = I ×V

Resistance Calculation Reading Resistorâ&#x20AC;&#x2122;s value

Band 2 Band 1

Band 4

Band 3

COLOUR

BAND 1 (Units)

BAND 2 (Tens)

BAND 3 (Multiplier)

Black

Brown

X 10

Red

X 100

Orange

X 1000

Yellow

X 10000

Green

X 100000

Blue

X 1000000

Violet

Grey

White

BAND 4 (Tolerance)

Gold

X 0.1

Silver

X 0.01

10 %

None

20%

Resistance Calculation Reading Resistor’s value

Band 2 Band 1

Band 3

Band 4

Eg. Band 1— Yellow (4), Band 2—Violet (7), Band 3—Red (2 zeros), Band 4—Silver Resistance of this resistor = 4700Ω ± 10% tolerance or 4.7kΩ ± 10% tolerance Range of resistance will be 4700 – 470 to 4700 + 470Ω => 4230 to 5170Ω

Resistance of a Circuit Resistors in Series Total Resistance in Series = R1 + R2 + R3 Which is larger than each of the resistor. R1

Resistance of a Circuit

Resistors in Parallel

1 1 1 1 = + + Total Resistance R1 R 2 R3 Total resistance will be smaller than each of the resistor. R1 R2 R3

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