Simple Output Devices TASK 1.Collect a set of Output Device cards. 2.Match each symbol to the...
-
Upload
milo-craig -
Category
Documents
-
view
217 -
download
1
Transcript of Simple Output Devices TASK 1.Collect a set of Output Device cards. 2.Match each symbol to the...
Simple Output Devices
TASK
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 NameEnergy Change
Device Type
Symbol Name Energy Change Device Type
M
bulb electrical light analogue
motor electrical kinetic
analogue
buzzer electrical sound digital
solenoid electrical kinetic
digital
Symbol Name Energy Change Device Type
loudspeaker
electrical sound analogue
relay electrical kinetic
digital
Relay Switch
Relay
A relay is a switch controlled by an electromagnet.
A coil of wire:
• carrying a current = magnet
• with no current = non magnet
Symbol:
Relay
M
230 Va.c.
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.
9 V
S
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.
: :. .
: :. .
to alarm
S
magnet
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.
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
Light Emitting Diode (LED)
LED
Symbol:
Energy Change: electrical light
Type: digital output device (only ON or OFF).
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)
electrons flow into point of
triangle to light LED
resistor in series
An LED is damaged if too large a current passes through.
A series resistor limits the size of the current, protecting the LED from damage.*** ***
Q1. (a) Which LED’s in the following circuits will light?
R
LED 1
R
LED 2R
LED 3
RLED 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.
LED’s are wired this way.
(d) When an LED does not light it is biased.
forward
reverse
protect the LED from damage
1 and 3
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.
VR + VLED = VSUPPLY
VS
0 V
VR
VLED** not on data sheet **
x
÷
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 2VLED
25VR V 3
mA 20I A 10 20 -3
?R
IV
R
IV
R R
3-10203
Ω 150R
V
I R
R IV
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.
V 2.2VLED
2.26VR V 3.8
mA 18I A 10 18 -3
?R
IV
R R
3-10183.8
Ω 211R
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 Ω
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 Ω
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 Ω
d
g
7 Segment Display
7 rectangular LED’s are arranged as follows to give a 7-segment display.
a
b
e c
f The number 3 is displayed by lighting
segments a, b, c, d and g
Energy Change: electrical light
Type: digital output device (segment ON or OFF).
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
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
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
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
solenoid
7-seg.
motor
Binary Numbers
Binary numbers consist of a series of 0’s and 1’s.
Consider the binary number 1101.
1 1 0 1
means 1 lot of 8
means 1 lot of 4
means no lots of 2
means 1 lot of 1
So we have as a decimal number: 8 + 4 + 0 + 1 = 13
8 4 2 1continue to
increase (double)
just in same way as we represent
decimlas by
H T U
7 8 9
** 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
Q1. Copy and complete the table of decimal and binary numbers:
Decimal Binary
00102
01117
111115
1001018
1011123
Q2. What decimal number is represented by the binary number:
(a) 0100 (b) 10014 9
Relay