Sheila Porter

1
PowerPoint Presentation III Electronic
Engineering l ll

• Sheila Porter
• Intel Ireland

2
Electronic Engineering

• Session 4 Electronic Engineering I
• Students explore simple
  circuitry with bulbs, batteries, wires and
  breadboards
• Session 5 Electronic Engineering II
• Students use switches, LEDs
  and motors and investigate their application in
  the world around them

Cordless Telephone
3
Session 4 Electronic Engineering I
Key Concepts in Electricity
1. A complete circuit is needed for an electric
current to flow.
2. A resistor will reduce the flow of current in
a circuit.
3. The voltage of a battery or power pack is a
measure of the 'push' that can make a current
flow the larger the voltage the larger the
current for a given resistance.
4. Current is not used up when it flows through
a circuit.
5. Not all electrical component obey Ohm's law,
e.g. silicon chips, capacitors, light-emitting
diodes (LEDs).
6. Circuits inside silicon chips can be turned
on or off by changing the voltage they sense
(rather than current).
4
Check Your Understanding

• Q.1 The diagram shows a battery and lamps
  connected to some wires.
• Why wont the bulbs light?
• What would you do to make the circuit work
  properly?

• A.1
• Circuit not complete
• Link wire and bulb

5

• Q.2 We measure the amount of current flowing
  through a circuit
• in amps (A).
• Suppose the circuit is made to work
  properly so that both bulbs light. Also suppose
  we measured the current flowing through the wire
  at P as one amp (1 A).
• What would you predict the size of the current to
  be at point Q?
• What would you predict the size of the current to
  be at point R?

A.2 (i) 1 A at Q (ii) 1 A at R
Current is not used up in a circuit
6

• Q.3 Assume you had built the circuit so that
  both bulbs were glowing. What do you think would
  happen if you connected a wire from P to Q?

A.3 The bulb would go out. The wire from P to Q
would have a much lower resistance than the bulb,
so almost all the current would go through the
wire and not the bulb. The other bulb would glow
more brightly.
7

• Q.4 Imagine the circuit was working properly,
  with both lamps glowing. Now imagine you replaced
  the 9 V battery by a 90 V battery. Write down
  what you think would happen, and why it would
  happen.

90 V Battery
A.4 The 90 V battery would drive a much greater
current through the circuit (about 10 times as
much). It is likely that so much current would
burn out the filaments of the bulbs, i.e., they
would glow very brightly for a brief moment and
then stop working.
8
Connections on a Breadboard
Horizontal row
No connection
Vertical row

• One or more horizontal rows of holes at the top.
  All these holes are connected together by a metal
  strip running underneath.
• One or more horizontal rows of holes at the
  bottom. These holes are also connected together.

• Two sets of holes in rows of five holes each,
  separated by a gap. These holes are connected
  vertically only. So, for example, two holes
  side-by-side are NOT connected.

• There is no connection across the gap.

9
Electrical Components
10
Building Simple Circuits

• Supplies
• Breadboard
• Battery
• Electrical
• wire
• 2 lamps
• 2 LEDs
• Procedure 1
• Build the circuit shown in the photo to make
  two lamps light.

Session 4, Activity A
11
LEDs Light-Emitting Diodes
Special type of diode which gives out light when
a small current flows through it (forward bias)
REMEMBER The cathode must be connected to the
terminal of the battery
12
LEDs Light-Emitting Diodes

• LEDs usually require a voltage of about 2 V to
  light
• Anything higher and they will burn out

• Ordinary LEDs are used with a protective resistor
  in series with them

• The LEDs in our investigations have built-in
  resistors for convenience

13
LEDs Light-Emitting Diodes

• Procedure 2
• Identify anode and cathode on LED
• Remove bottom lamp from breadboard
• Insert LED and note whether
• it lights
• Turn the LED around and note whether it lights
• Replace both lamps with LEDs

REMEMBER The cathode must be connected to the
terminal of the battery
Session 4, Activity A
14
Uses of LEDs
15
Using Simple Switches - Push Switch

• Supplies
• Circuit from previous investigation
• 1 push switch

• Procedure
• Try connecting the push switch as shown in the
  photo
• Does it matter which way round the switch is put
  into the circuit? (Try it.)

Uses of push switch - camera, flashlight, etc.
Session 4, Activity B
16
Using Simple Switches - Micro Switch
Attach 3 leads as shown in the diagram

• Lever can be used to magnify small movements
• Micro switch is very sensitive
• Can be used, e.g., to sound an alarm if attached
  to a window with even the slightest opening.

Session 4, Activity B
17
Using Simple Switches - Micro Switch

• Supplies
• Circuit from previous investigation
• 1 micro switch

• Procedure
• Try connecting the
• micro switch as shown
• in the photo
• Complete the table
• below

Wires used What happens to the lamps before the lever is pressed? What happens to the lamps after the lever is pressed?
1 and 2
1 and 3
2 and 3
18
Using Simple Switches - Micro Switch
Wires used What happens to the lamps before the lever is pressed? What happens to the lamps after the lever is pressed?
1 and 2 Light off Light on
1 and 3 Light on Light off
2 and 3 Light off Light off
Pins 1 and 2 are known as normally open
(NO) Pins 1and 3 are known as normally closed
(NC)
19
Using a Silicon Chip

• 4093 silicon chip Quad, 2-input NAND logic chip

• This chip contains four logic gates, each with
  two inputs

• It has 14 legs (pins)
• Students use pins 1, 2, 3, 7 and 14

• Pins 1 and 2 are inputs, pin 3 is the output, of
  one gate

• The output depends on the inputs

20
How the Output Depends on the Inputs

• Supplies
• Breadboard Battery
• Electrical wire
• 4093 silicon chip
• LED
• Procedure
• Build the circuit shown in the photograph.
• Complete the table in the workbook.

Input to pin ON - when connected to of
battery OFF- when connected to of battery
Session 4, Activity C
21
Input Pattern for the 4093
Input to pin ON when connected to of
battery OFF when connected to of battery
Pin 1 Pin 2 Pin 3 (output)
OFF OFF
ON OFF
OFF ON
ON ON
ON
ON
ON
OFF
Session 4, Activity D
22
Session 5 Electronic Engineering Il

• Reed Switches

• Two thin pieces of metal sealed in a vacuum in a
  glass tube
• When a magnet is brought near the two metal
  contacts they are brought together and connected

23
A Reed Switch Circuit

• Supplies
• As Session 4, Activity C
• Reed Switch
• Procedure
• Build the circuit shown in the diagram.
• Bring the magnet near to the reed switch and
  observe what happens.
• Swap the LED for a

buzzer
Session 5, Activity A
24
Making an LED Flash

• To do this you need to use a capacitor and a
  resistor

Capacitors Store charge and consist of two
conducting surfaces separated by an insulator.

• When connected to a battery a capacitor charges
  up until it reaches the same voltage as the
  battery

• When a conductor, e.g., a bulb, is connected to
  the charged capacitor current will flow from one
  plate to the other

• The charging and discharging of a capacitor can
  be slowed down by placing a resistor in series
  with it in the circuit.

-
25
Resistors

• Resistance of a circuit is how difficult it is to
  drive a current through it. The bigger the
  resistance the smaller the current that can flow
  for a given voltage across the circuit.

• Resistance is measured in ohms (O). When we want
  to reduce the current flowing in a circuit we
  insert a resistor.

• Some resistors are made of wire but most are made
  of carbon. The coloured bands tell us what the
  resistance of each resistor is.

26
Resistor Colour Codes

• Two series4-band and 5-band
• 4- band code

• Bands 1 and 2 first two digits of the value
• band 3 the powers of 10. Band 4 the quality
  of the resistor
• Gold band 5
• Silver band 10.
• Band 4 is separated from the other bands, to tell
  us at which end to start counting from

Colour Value
Black Brown Red Orange Yellow Green Blue Violet Grey White 0 1 2 3 4 5 6 7 8 9
27
Making an LED flash

• Supplies
• Breadboard
• Battery
• Capacitor
• Resistor
• 4093 silicon chip
• LED

• Procedure
• Build the circuit shown in the photograph
• Investigate how
• the flashing rate changes if you change the
  resistor

Session 5, Activity B See website-Electronic
Fixes
28
Controlling a Motor
Chip 2003

• Pin 8 must be connected to the negative of the
  battery
• Pin 9 must be connected to the positive of the
  battery

29
Controlling a Motor

• Supplies
• Components from previous session
• Electric motor
• 2003 chip
• Procedure
• Build circuit as in diagram
• Use pin 1 to turn the motor on and off
• Connect the motor between the ve of the battery
  and pin 16
• Do not allow the motor to run longer than 10
  seconds at a time

Session 5, Activity C
30
Ireland
Education