Unit 1 – Fundamentals Electronics. Electricity – study of the flow of electrons. Electronics –...

Unit 1 – Fundamentals Electronics

Electricity – study of the flow of electrons.

Electronics – study of the control of electron flow.

Conductor - Material w/ loosely held e-; e- flow easily (metals)

Insulator - Material w/ e- tightly bound to the nucleus (nonmetals)

For e- to flow in a conductor there must be…

1. A difference in electric potential (voltage) b/w points.

2. A complete path (circuit)

Voltage (V) - Push of electrons (volts)

Current (I) - Flow of electrons (amps)

Resistance (R) - Restriction of electron flow (ohms, Ω)

Power (P) - Electrical energy per time (watt)

also known as electromotive force (emf)

V = I x R

Twinkle twinkle little star, voltage equals I times R

Ohm’s Law

Power equals current times voltage

Watts = amps x volts

P = I x V

Power Law

Metric Prefixes

Mega – 1,000,000 = 106

Kilo – 1,000 = 103

-------------

Milli – 1/1,000 = 0.001 = 10-3

Micro – 1/1,000,000 = 0.000001 = 10-6

Nano – 1/1,000,000,000 = 0.000000001 = 10-9

Pico – 10-12

ExamplesCalculate the current (in amps) in a 200 ohm

resistor in a 120 Volt circuit.

Express this answer in milliamps (mA).

ExamplesCalculate the current in a 100 Watt light bulb on a

120 volt circuit.

ExamplesCalculate the voltage across a 10 kilo-ohm resistor

that has 0.125 amps of current through it.

Direct Current (DC)Electron flow in 1 direction (cells, batteries)

Types of Current

Conventional Current – flows from pos. to neg (Thanks Ben F.)

Electron Flow – flows from neg. to pos.

Alternating Current (AC)

Electron flow constantly changes direction at certain frequency (Hertz).

DC Power (Battery)

Resistor

Schematic Symbols

AC Power

http://wiki.4hv.org/index.php/File:Resistors.jpg

Cell - Converts chemical energy to electrical energy.

Cells vs. Batteries

AAA, AA, C, D all are rated 1.5 Volts

Battery - Group of 2 or more cells connected together.

9 Volt battery consists of six 1.5 cells

Cell & BatteriesCapacity - Amount of electricity that a battery will give off before fully

discharging; measured in Amp-hours.

The capacity of a battery depends on its discharge rate.

Discharge Rate - Rate at which current is drawn from battery.

AAA

In theory, a AAA can produce 1.25 A for 1 hour.

In reality, a AAA can’t produce 1.25 A.

AA

C

D

9-V 625 mAh

1250 mAh

2850 mAh

8350 mAh

20500 mAh

@ lowest discharge rate (25 mA)Capacity

Battery Capacities (Energizer)

9-Volt

AA

ASSIGNMENT:

Worksheet #1: Ohm’s Law

The Resistor Color CodeMemorize this code!!

47000 Ω or 47 kiloΩ

Resistors

• A resistor is typically used to control the amount of current that is flowing in a circuit.

• Resistance is measured in units of ohms ()

21

Resistors: Types and Package Styles

22

Surface Mount Resistors

Variable Resistors(potentiometer)

Carbon Film Resistors

5 Bands

Carbon Film Resistors

4 Bands

Resistors: Size Comparison

23

Determining A Resistor’s Value

Color Code

• Resistors are labeled with color bands that specify the resistor’s nominal value.

• The nominal value is the resistor’s face value.

Measured Value

• A digital multi-meter can be used to measure the resistor’s actual resistance value.

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How To Read A Resistor’s Value

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Resistor Color Code

Resistor Value: Example #1Example:

Determine the nominal value for the resistor shown.

26



27

Solution:

10 x 100 5%

1000 5%

1 K 5%



28



29

Solution:

39 x 100K 5%

3900000 5%

3.9 M 5%


Determine the color bands for a 1.5 K 5% resistor.

30

?? ??


Determine the color bands for a 1.5 K 5% resistor.

31

Solution:1.5 K 5%

1500 5%

15 x 100 5%

1: Brown

5: Green

100: Red

5%: Gold

?? ??

Potentiometers – 3-terminal variable resistor

The resistance will be printed on it.

Rheostat – uses the center and 1 outer terminal

The center terminal is called the ‘wiper’ or center tap.

Inside a potentiometer

http://upload.wikimedia.org/wikipedia/commons/c/c3/Pot1.jpg

Potentiometer Schematic Symbol

Rheostat Schematic Symbol

Standard Resistor Values

10 12 15 18 22 27 33 39 47 56 68 82

100 120 150 180 220 270 330 390 470 560 680 820

1k 1.2k 1.5k 1.8k 2.2k 2.7k 3.3k 3.9k 4.7k 5.6k 6.8k 8.2k

10k 12k 15k 18k 22k 27k 33k 39k 47k 56k 68k 82k

100k 120k 150k 180k 220k 270k 330k 390k 470k 560k 680k 820k

1M 1.2M 1.5M 1.8M 2.2M 2.7M 3.3M 3.9M 4.7M 5.6M 6.8M 8.2M

Don’t assume all the resistors in the tray are what the tray claims.

Resistors are normally rated for ¼ or ½ watt.

For most circuits, a ¼ watt resistor will work.

Digital Multimeter (DMM)

Measuring Electrical Quantities

Voltage Measure across (parallel) device

Current Measure in series with device (break open circuit

Resistance Measure across the device (power off!)

Voltage DropVoltage across a device

Open No electron flow (OFF)

Closed Electrons are flowing (ON)

Series 1 path for electron flow. Each device receives same I, Vdrop depends on R

Parallel

Short

More than 1 path for electon flow. Each path receives the same voltage.

Electrons bypass the device.

Types of Circuits

Adding Resistors in Series

1 2 ...TR R R Adding Resistors in Parallel

1 2

1 1 1...

TR R R

The total resistance of a parallel circuit decreases as more resistive paths are added.

Series Circuit Example

R1 = 100

R2 = 2203 V

1. Calculate the total resistance of the circuit.

2. Calculate the current flowing through R1 & R2.

3. Calculate the voltage across R1 & R2.

4. How much power is used by R1 & R2?

Parallel Circuit Example

R1 = 100

R2 = 220

3 V

1. Calculate the total resistance of the circuit.

2. Calculate the current flowing through R1 & R2.

3. Calculate the voltage across R1 & R2.

4. How much power is used by R1 & R2?

Voltage DropVoltage across a device in a circuit.

SolidBare, Insulated or Enameled

Wire Types

StrandedInsulated

Cable2 or more insulated wires bound together.

American Wire Gauge (AWG) Indicates wire diameter (thickness).

Wire Sizes

The smaller the wire, the larger the AWG number.

Thick wires can safely handle more current.

Wire Sizes

Toggle

Switches

Slide

Switch –

device placed in a circuit to open and close the circuit.

Push Button

Rocker

SwitchesKnife

Rotary

Reed (Magnetic)

Tilt (mercury or ball)

Switches

Switches

SPDT – Single Pole Double Throw

Pole – set of 2 contacts that belong to a single circuit.

Switches

Throw – one of two or more positions that a switch can be in.

SPST – Single Pole Single Throw

Switches

SPDT – Single Pole Single Throw

aka “Three Way Switch”

Switches

DPDT – Double Pole Double Throw

Switches

SPST SPDT

Normally Open – not ON until switch is pressed; “press to make”

Normally Closed – ON until switch is pressed; “press to break”

NO NC

Momentary pushbutton switches

Tactile SwitchesUpper pins connect to lower pins when pressed.

SolderingJoining of metals by using a low-melting point metal alloy (solder)

Soldering Iron Soldering Gun

SolderSolder is an alloy of TIN (~60%) and LEAD (~40%)

Rosin Core Solder (NOT ACID CORE!)

Solder melts around 200° F

Useful Soldering Items

Soldering Iron Stand Helping Hands

How to Solder

1. CLEAN SURFACES to be joined (steel wool or sandpaper; lacquer thinner if necessary)

2. APPLY HEAT. Heat up connection using a clean soldering-iron tip.

3. APPLY SOLDER. The solder should touch the connection, not the iron tip. Solder will flow to the hot spot.

4. REMOVE SOLDER.

5. REMOVE HEAT. Do not move connection while it cools (solidifies).

How to Solder 2 Wires Together


Use the Helping Hands


Apply Heat


Apply Solder, Remove Solder, Remove Heat

A Good Soldered Connection

1. Does not have a ball or lump of solid solder.

2. Is shiny. Dull solder points indicate the wires moved during cooling, making a weak connection.

Heat ShrinkingHeat shrink tubing, when heated, will shrink to about 50% of its original size.

Placed over an open connection between wires and then shrunk (using heat gun) to insulate the connection.

Desoldering

Desoldering Wick (copper braid)

Removing the solder from a connection.

Desoldering Bulb (copper braid)

ASSIGNMENT:

1. Solder solid leads onto a battery snap.

Red wire Red wire

Black wire Black wire

Apply red and black heat shrink tubing.

Show Tischer for credit.

2. Solder two black wires to a speaker.

Breadboard or Solderless Circuit Board

Positive bus

Negative bus

Breadboard or Solderless Circuit Board

Breadboard - Used to build circuits temporarily.

- Do not run 9 volts across anything; always use a resistor.

- Do not work on live circuits; have an ON/OFF slide switch to check if circuit works.

- Use 22 AWG solid wire; do not insert wire in breadboard more than ¼”

- Keep your circuits neat; don’t use wire that is longer than necessary.


- Keep your circuits neat;

don’t use wire that is longer than necessary.

minimize the amount of wire

build circuit to resemble the schematic layout

highlight schematic to show what you’ve done


- Do not run 9 volts across anything; always use a resistor.

- Do not work on live circuits; have an ON/OFF switch to check if circuit works.

- Use 22 AWG solid wire; do not insert wire in breadboard more than ¼”

- Keep your circuits neat; don’t use wire that is longer than necessary.

What resistor should be used for a 9-V battery to run an LED?

We need a resistor that will have a voltage drop of (9 – 2.2 V) = 6.8 V

We also need a safe current of around 20 mA in the circuit.

R = V/I = 6.8 V/0.020 A

= 340 ohms

390 or 470 ohms would work.

1. Build this circuit

2. Add a potentiometer in series with the resistor

3. Substitute a photocell for the resistor.

Add a SPDT slide switch to the breadboard

Unit 1 – Fundamentals Electronics. Electricity – study of the flow of electrons. Electronics –...

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Transcript of Unit 1 – Fundamentals Electronics. Electricity – study of the flow of electrons. Electronics –...