university of ulster (jordanstown) technology & design pgce electronics / modelling in livewire...
TRANSCRIPT
University of Ulster (Jordanstown) Technology & Design PGCE
Electronics / Modelling in Livewire & PCB Wizard
R.A. Moffatt.
Automatic Switching:-
Light / Temperature Sensing - Transistor Projects.
Live Wire
University of Ulster (Jordanstown) Technology & Design PGCE
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
Automatic Switching: Transistor Project
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
We
Are
Learning
To
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
ElectronicsWALT
University of Ulster (Jordanstown) Technology & Design PGCE
WILF:
What
I am
Looking
For
• 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
Electronics
University of Ulster (Jordanstown) Technology & Design PGCE
Preset – Variable Resistor
Light Dependant Resistor
Single-Pole-Single-Throw Switch
Componentsymbols
Potential Divider
9V
0V
University of Ulster (Jordanstown) Technology & Design PGCE
X
Y
Y
X
B B
Water Pipe Analogy:
Diagram extracted from Making Things Work by Ken Shooter & John Saxton
The Potential Divider
University of Ulster (Jordanstown) Technology & Design PGCE
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)
Emitter (e)
Base (b)
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
The Transistor
Technology Education Centre 05.
University of Ulster (Jordanstown) Technology & Design PGCE
The Transistor
Small Voltage in
Large Voltage
http://www.satcure-focus.com/tutor/page4.htm
PNP Transistor
B
C
E
symbol Saturated = ‘fully on’
B
C
E
0.6V
9V
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 I Iis a measure of the amplification which we call the transistors current gain. The symbol for the transistor current gain is
cb
hfe = IcIb
hfe
= 0.5 A0.00025 A
= 200
(0.00025A) (0.05A)
University of Ulster (Jordanstown) Technology & Design PGCE
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
Transistor
LDR
V/Resistor
BULB ‘off’
University of Ulster (Jordanstown) Technology & Design PGCE
Bulb-’on’ when Light
BULB ‘on’
Transistor
LDR
V/Resistor
University of Ulster (Jordanstown) Technology & Design PGCE
University of Ulster (Jordanstown) Technology & Design PGCE
LED-’off’ when Light shines on LDR
Transistor
LDR
VR
LED ‘off’
University of Ulster (Jordanstown) Technology & Design PGCE
LED-’on’ when Dark
University of Ulster (Jordanstown) Technology & Design PGCE
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
voltage is high enough to switch on the
transistor – therefore the bulb is
switched ‘on’.
Ex 1: Potential Divider / Dark Light ‘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?
‘OFF’
‘ON’
University of Ulster (Jordanstown) Technology & Design PGCE
Ex 2: Dark Sensor: Circuit 4 from 112 Circuit Designs – M. Lynch
TIP 121 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
Real World Normal
PCB: Printed Circuit Board
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
Moisture.pdf
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
In a Darlington pair circuit, two transistors are wired together to provide better Switching.
Darlington Pair Driver
University of Ulster (Jordanstown) Technology & Design PGCE
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.
Electronics Year 9 Test
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/8181http://www.new-wave-concepts.com/br_files.html