Download Automatic Switching: Transistor Project

Live Wire
Electronics / Modelling in
Livewire & PCB Wizard
Automatic Switching:-
Light / Temperature Sensing Transistor Projects.
University of Ulster (Jordanstown) Technology & Design PGCE
R.A. Moffatt.
Automatic Switching: Transistor Project
Aims:
To understand the concept of automatic switching /
sensing in electronic circuits
To practice modelling basic electronic switching circuits
using the Live Wire and PCB Wizard software
To construct (PCB’s) printed circuit boards
University of Ulster (Jordanstown) Technology & Design PGCE
Automatic Switching: Transistor Project
You will have an opportunity to:Design a temperature/light sensing circuit.
To manufacture a printed circuit board.
Two of the circuits respond to a change in light levels and
the other two respond to a change in temperature levels.
University of Ulster (Jordanstown) Technology & Design PGCE
Practically every modern Intel Pentium processor
main board features a temperature sensor
developed at Delft University of Technology. The
sensor detects when the processor starts to
become too hot, and switches on a fan to cool it
down. As soon as the temperature drops to an
acceptable level, the fan is switched off. The
temperature sensor was developed by Dr. Anton
Bakker, who in April 2000…
University of Ulster (Jordanstown) Technology & Design PGCE
Our Learning Intentions
•
•
•
•
•
•
know how to use the Live Wire and PCB Wizard
software
how to design automatic control circuits
understand input sensors and transistor switching
an understanding of resistor colour codes using four
and five band resistors
circuit building skills developed by using the
soldering iron
practice at following detailed test procedures
University of Ulster (Jordanstown) Technology & Design PGCE
WALT
We
Are
Learning
To
Electronics
To understand the concept of a
potential divider which provides
automatic switching of electronic
circuits
This is because .. We can learn how to design electronic
circuits and systems using automatic
switching for our project work
Remember to:
• refer to the water analogy to help
understand how the Potential divider
works
University of Ulster (Jordanstown) Technology & Design PGCE
WILF:
What
I am
Looking
For
Electronics
• an understanding of the potential divider as
a sensor / automatic switch
• the ability to sketch a circuit diagram of an
automatic temperature / light sensing
sensor circuit
• to be able to model and test an automatic
switching circuit
• to make a PCB and build a sensing circuit as
an example of a transistor-based control
system
University of Ulster (Jordanstown) Technology & Design PGCE
Single-Pole-Single-Throw Switch
9V
Preset – Variable Resistor
Component
symbols
Light Dependant Resistor
0V
Potential Divider
University of Ulster (Jordanstown) Technology & Design PGCE
The Potential Divider
Water Pipe Analogy:
X
X
B
B
Y
Y
University of Ulster (Jordanstown) Technology & Design PGCE
Diagram extracted from Making Things Work by Ken Shooter & John Saxton
The Transistor
Transistors are
semiconductor devices.
This means that they have
a resistance to the flow of
electrons – current.
However they become
conductors if a small
voltage is provided across
two of the legs – the base
and the emitter.
Collector (c)
Base (b)
Emitter (e)
Symbol for the n-p-n transistor
You can use the transistor as a high speed switch if a small voltage of
0.6 – 1.6V is applied to the base leg as shown below
University of Ulster (Jordanstown) Technology & Design PGCE
Technology Education Centre 05.
The Transistor
Large Voltage
C
9V
B
PNP Transistor
0.6V
C
Small Voltage in
E
B
symbol
Saturated = ‘fully on’
E
http://www.satcure-focus.com/tutor/page4.htm
University of Ulster (Jordanstown) Technology & Design PGCE
Transistor Gain:
We know that a small current flowing at the base of the transistor
will ‘turn on’ a large collector current. This is known as current Amplification.
The ratio Ic
Ib
is a measure of the amplification which we call the transistors current
gain. The symbol for the transistor current gain is hfe
hfe = Ic
Ib
= 0.5 A
0.00025 A
= 200
University of Ulster (Jordanstown) Technology & Design PGCE
(0.00025A)
(0.05A)
The Transistor
http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/info/comp/active/BiPolar/page1.html
University of Ulster (Jordanstown) Technology & Design PGCE
http://www.allaboutcircuits.com/vol_3/chpt_4/3.html
University of Ulster (Jordanstown) Technology & Design PGCE
Bulb-’off’ when Dark
BULB
‘off’
LDR
Transistor
V/Resistor
University of Ulster (Jordanstown) Technology & Design PGCE
Bulb-’on’ when Light
BULB
‘on’
V/Resistor
Transistor
LDR
University of Ulster (Jordanstown) Technology & Design PGCE
University of Ulster (Jordanstown) Technology & Design PGCE
LED-’off’ when Light shines on LDR
LED
‘off’
VR
Transistor
LDR
University of Ulster (Jordanstown) Technology & Design PGCE
LED-’on’ when Dark
University of Ulster (Jordanstown) Technology & Design PGCE
Ex 1: Potential Divider / Dark Light ‘on’
‘OFF’
In the light the voltage between the
base and the emitter leg of the
transistor is 657mV or 0.65V. For this
transistor the voltage is not enough to
switch it on – therefore the bulb
remains off.
In the darkness the voltage between the
base and the emitter leg of the
transistor is 739mV or 0.739V. This
‘ON’
University of Ulster (Jordanstown) Technology & Design PGCE
voltage is high enough to switch on the
transistor – therefore the bulb is
switched ‘on’.
a) Model the circuit using Live Wire
as shown and test!
a) Draw this circuit diagram in your
folder and explain how it works?
Ex 2: Dark Sensor: Circuit 4 from 112 Circuit Designs –
TIP 121
M. Lynch
TIP 121
Light level low LED will be ‘on’
a) Model this circuit and test using Live Wire
b) Draw this circuit diagram in your workbook and explain how it works?
c) Convert this circuit to a PCB layout using PCB Wizard
University of Ulster (Jordanstown) Technology & Design PGCE
PCB: Printed Circuit Board
Real World
Normal
PCB Wizard
University of Ulster (Jordanstown) Technology & Design PGCE
Printed Circuit Board
University of Ulster (Jordanstown) Technology & Design PGCE
Circuit 5 A Light Sensing Transistor
University of Ulster (Jordanstown) Technology & Design PGCE
M. Lynch
Play the AVI file to help understand how this circuit works?
University of Ulster (Jordanstown) Technology & Design PGCE
Double-Click the PDF icon to access
the data sheet
House plants can suffer if
owners do not give them the
right amount of water.
Houseplants can die if they
do not receive enough water,
and they can rot if over
watered.
University of Ulster (Jordanstown) Technology & Design PGCE
Moisture Tester
‘on’
moisture level
University of Ulster (Jordanstown) Technology & Design PGCE
University of Ulster (Jordanstown) Technology & Design PGCE
University of Ulster (Jordanstown) Technology & Design PGCE
Darlington Pair Driver
In a Darlington pair circuit, two transistors are wired together to
provide better Switching.
University of Ulster (Jordanstown) Technology & Design PGCE
Electronics Year 9 Test
1) Make sketches of a 1K, 2k2, 680R and 470R resistor
include the colour code for each
2) Explain the function of a resistor in an electronic circuit?
3) Draw the two component symbols necessary and in the
correct order to make a potential divider that sounds a
buzzer when light shines on the LDR? One of these
component symbols have been drawn for you.
University of Ulster (Jordanstown) Technology & Design PGCE
4) Explain how the circuit shown below works?
5) Suggest two uses for this type of circuit?
6) What is the trigger voltage for a BS 108 Transistor?
7) Sketch the symbol for a transistor and label the legs: emitter, collector, base
University of Ulster (Jordanstown) Technology & Design PGCE
8) An electronic sensor is required for an elderly persons
room that sounds an alarm when the room temperature
drops to a certain level or gets ‘too cold’. Draw and
complete the circuit diagram using symbols to show the
type of sensor required?
9) Name each of the components used in your design?
University of Ulster (Jordanstown) Technology & Design PGCE
10) Name each of the component shown below and explain briefly their function
when used in an electronic circuit?
University of Ulster (Jordanstown) Technology & Design PGCE
http://www.circuitspecialists.com/prod.itml/icOid/8181
http://www.new-wave-concepts.com/br_files.html
University of Ulster (Jordanstown) Technology & Design PGCE