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Simple Output Devices

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Simple Output Devices TASK Collect a set of Output Device cards. Match each symbol to the correct name, energy change and type (digital or analogue). – PowerPoint PPT presentation

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Title: Simple Output Devices


1
Simple Output Devices
  1. Collect a set of Output Device cards.
  2. Match each symbol to the correct name, energy
    change and type (digital or analogue).
  3. Get it checked.
  4. Complete the following table with the correct
    information

Symbol Name Energy Change Device Type

2
Symbol Name Energy Change Device Type

bulb
analogue
motor
analogue
buzzer
digital
solenoid
digital
3
Symbol Name Energy Change Device Type

analogue
loudspeaker
relay
digital
4
Relay Switch
  • A relay is a switch controlled by an
    electromagnet.
  • A coil of wire
  • carrying a current magnet
  • with no current non magnet

Symbol
5
Example of Relay Use A high voltage mains motor
is switched on when switch S is closed. The small
current in the 9V circuit makes the electromagnet
become magnetic. This closes the switch and
starts the motor.
6
Reed Relay
The reed relay uses a permanent magnet to open or
close a switch. This type of relay is used in
burglar alarm systems to detect when a door is
opened.
7
Experiment When the door is closed the magnet is
close to the reed relay and switch S is
open. When the door is opened, the magnet moves
away from the relay, causing switch S to close
setting off the alarm.
8
Solenoid
A solenoid is a coil of wire surrounding a metal
rod. It is an electromagnetic device that moves a
metal rod backwards and forwards.
  • Examples of Solenoid Use
  • car central locking
  • safe locks
  • steering on radio controlled cars
  • railway points

9
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10
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11
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12
Light Emitting Diode (LED)
LED Symbol Energy Change electrical light Typ
e digital output device (only ON or OFF).
13
Wiring up an LED An LED only conducts when it is
connected the proper way around in a circuit.
LED lights (FORWARD BIAS)
LED does not light (REVERSED BIAS)
An LED is damaged if too large a current passes
through.
14
Q1. (a) Which LEDs in the following circuits
will light?
LED 3
LED 1
LED 2
R
R
R
R
LED 4
(b) What is the purpose of the resistor R in the
above circuits? (c) When an LED lights it is
said to be biased. LEDs
are wired this
way. (d) When an LED does not light it is
biased.
protect the LED from damage
forward
1 and 3
reverse
15
Calculating Size of Resistor
The resistor and LED are in series. So the
voltage across the resistor and the voltage
across the LED must add up to give the supply
voltage.
VS
not on data sheet
0 V
16
Example 1 An LED can withstand a maximum current
of 20 mA at 2 volts. Calculate the minimum value
of resistor required when the LED is connected to
a 5 V supply.
V
I
R
17
Example 2 An LED can take a maximum current of 18
mA at 2.2 V. Calculate the minimum value of
resistor required to protect the LED when it is
connected to a 6V supply.
18
Q1. The maximum voltage allowed across an LED is
2.3 V and the current through it must not exceed
10 mA. The LED is connected to a 5 V
supply. Calculate the value of the resistor R
connected in series with the LED.
270 O
Q2. An LED takes 10 mA and 1.5 V to work
properly. What value of series resistor is
required if a 6 V battery is used.
450 O
Q3. An LED and resistor are connected in series
to a 9 V supply. The maximum voltage across the
LED is 1.8 V and the current through the LED
must not exceed 12 mA. Calculate the value of
resistor required to protect the LED.
600 O
19
7 Segment Display
7 rectangular LEDs are arranged as follows to
give a 7-segment display.
a
f
b
The number 3 is displayed by lighting segments a,
b, c, d and g
g
e
c
d
Energy Change electrical light Type digital
output device (segment ON or OFF).
20
Experiment 1 Making Numbers Using a 7-segment
display, display each number from 0 9 in turn
completing the table below.
Digit Segments Lit

0
a b c d e f
1
b c
2
a b g e d
3
a b c d g
4
f g b c
5
a f g c d
6
a f e d c g
7
a b c
8
a b c d e f g
9
a b c f g
21
Experiment 2 - Making Letters Make as many
letters as you can on the 7-segment display
completing the following table.
Letter Appearance Segments Used

A
a b c e f g
22
Which Output Device?
Selecting Output Devices Here is a list of output
devices
buzzer, lamp, motor, relay, solenoid
Which output device could be used
to (a) indicate required cooking time for oven
is complete (b) move conveyor belt at
supermarket (c) stop and start movement of
conveyor belt at supermarket.
buzzer
motor
relay
23
Q1. Give a suitable output device for each of the
following situations (a) an audible warning
when an incubator become too hot or
cold (b) a power on indicator for a
stereo (c) switch on a high current circuit
using a small current (d) indicator of
which TV channel is selected (e) to push chosen
sweets to hatch in a vending machine (f) run
a conveyor belt around a bottling factory.
buzzer
LED
relay
7-seg.
solenoid
motor
24
Binary Numbers
just in same way as we represent decimlas by H T
U 7 8 9
Binary numbers consist of a series of 0s and
1s. Consider the binary number 1101.
continue to increase (double)
8
4
2
1
1 1 0 1
means 1 lot of 1
means 1 lot of 8
means no lots of 2
means 1 lot of 4
So we have as a decimal number 8 4 0 1 13
25
You must know the binary for numbers from 0 to
9

8 4 2 1

Decimal
Binary
0
0
0
0
0
1
0
0
0
1
2
0
0
1
0
3
0
0
1
1
4
0
1
0
0
5
0
1
0
1
6
0
1
1
0
7
0
1
1
1
8
1
0
0
0
9
1
0
0
1
26
Q1. Copy and complete the table of decimal and
binary numbers
Decimal Binary

0010
2
0111
7
1111
15
10010
18
10111
23
Q2. What decimal number is represented by the
binary number (a) 0100 (b) 1001
4
9
27
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