Topic 1.2 – Electronic Sub-Systems. Learning Objectives: At the end of this topic you will be able to; Use the following sub-systems as part of a block diagram; o Input units: light, temperature, rotation, magnetic, moisture, sound, pressure pad/switch, and pulse generator. o Output devices: lamp, buzzer, motor, solenoid, and LED. o Signal processing: inverter, AND gate, OR gate, latch, time delay and comparator. State the function of a transducer driver. The following objectives have been reproduced from Topic 1.1, as they are more appropriate for assessment in this unit. describe possible applications of an electronic system from a block diagram; produce a block diagram for a system to solve a given problem; design and test electronic systems. 1
Transcript
Topic 1.2 – Electronic Sub-Systems.
Learning Objectives:
At the end of this topic you will be able to;
Use the following sub-systems as part of a block diagram;o Input units: light, temperature, rotation, magnetic, moisture,
sound, pressure pad/switch, and pulse generator.o Output devices: lamp, buzzer, motor, solenoid, and LED.o Signal processing: inverter, AND gate, OR gate, latch, time
delay and comparator. State the function of a transducer driver.The following objectives have been reproduced from Topic 1.1, as they are more appropriate for assessment in this unit. describe possible applications of an electronic system from a
block diagram; produce a block diagram for a system to solve a given problem; design and test electronic systems.
In this section we will investigate a range of electronic sub-systems, that can be linked together to make much bigger systems to solve problems. You should remember from topic 1.1 that there are three sections to an electronic system:
i. Input Sensors.ii. Signal Processing.iii.Drivers.iv.Output Devices.
You might be working on Alpha, E&L, or you might use a simulation like Control Studio. All of these systems have a range of input, process, driver and outputs. These notes are intended to be non-system specific and it should be possible to adapt all of the activities to any system.
We will look at Input Sensors and output devices first as these provide the interface with the real world. We will look at the signal processing units later.
Input Sensing Units
The processing section of an electronic system can only process electrical signals. The Input Sensing Units convert non-electrical signals, e.g. light, into an electrical form.
Input Signal
e.g. Light
Input Sensor
e.g. Light Sensor
Electrical
Signal
The Input Sensing Units can be subdivided into two types. They are described on the following page:
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Topic 1.2 – Electronic Sub-Systems.
(i) Digital Type:
The signal coming out of such boards can only have one of two values i.e. 0V or +5V.
We represent the changes in voltage that occur in a digital system by the symbols on the right.
(ii) Analogue Type:
The signal coming out of these boards can vary anywhere between 0V and +5V, depending on the input signal level. The level of the electrical signal from these boards is a representation (an analogue) of the input signal.
We represent the changes in voltage that occur in an analogue system by the symbols on the right.
Voltages are measured with respect to the negative (-) line. This is often referred to as the zero volt line (0V).
If a voltage is near the 0V line, say less than 2 volt, the point is said to be LOW. If it is near the positive line, say greater than 3 volt, it is said to be HIGH.
The signal coming out of the processing section of a system is usually HIGH or LOW. Output units receive this signal and can change the electrical signal into some other form e.g. the bulb unit will convert the electrical signal into heat and light energy.
Output Signal
e.g. Heat/Light
Output Device
e.g. Bulb Unit
Electrical
Signal
Most of the Input Sensing Units cannot supply sufficient current to directly drive the Output Units. Later on you will be using output switching devices (drivers). These units can take a voltage signal from the Input Sensing Units or other processing blocks and boost it so that the signal can drive any of the Output Units.
The function of the input sensing units and the output devices will be investigated in the assignments.
COMPLETE ASSIGNMENTS 1.2A, 1.2B & 1.2C
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Topic 1.2 – Electronic Sub-Systems.
Practical Work 1.2A : Investigating Input Sensors.
It has been assumed that you will have been shown how to make the basic setup of whichever system you are using.
Activity 1a : (For use with Alpha Kit)
a. Set up the following arrangement with the voltmeter on suitable range (20V). Use yellow alpha links unless told otherwise.
9 - 12VAC/DC
Power Supply Regulator
+
_
+
_ _
+
Switch Unit
+_
b. Switch on the Power Supply.
c. Record the voltage reading on the voltmeter. .........................................
d. Using your finger, press the switch and record below the reading on the voltmeter.
a. Now try to make the following circuit using an analogue sensor.
b. You will have to insert a <Sensor Unit>, and <Light Sensor> from the
<Insert> menu and link them in the same way as linking the multimeter.
c. Switch on the simulator, using the button.
d. Set the variable resistor on the Light Sensing Unit to near mid-position (Arrow pointing upwards). Adjust the setting of the slider alongside the light sensor, set this to Light
e. Record the voltage reading on the voltmeter.......................................
f. Now change the light level setting to Dark and record below the reading on the voltmeter.
The function of the unit is summarised in the following table.
Unit Type Action
H
L
Signal level from unit fallsgradually when window isInput
(Analogue)
LightSensing
Unit(11)
covered
Activity 3:
Use whichever system you have to investigate the other Input Sensing Units listed in the table on the following page. The signal coming from each can be investigated using a voltmeter, as we have done in the previous examples.
In each case complete the table to show if the unit is an analogue or digital input sensing device and write a sentence which describes its action. Start by copying in the two results you already know.
Unit Type Action
Switch Unit(13)
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Topic 1.2 – Electronic Sub-Systems.
Light Sensing Unit(11)
Input Voltage Unit(10)
Moisture / Rain Sensor
(16)
Temperature Sensor
(17)
Reed / Magnetic Switch(19)
Note : Control Studio has additional input units to these listed in the table which you might want to investigate, e.g. rotation sensor, although these will not be required for the examination.
There are sometimes alternative names used for a number of these input units, these are listed below. Ask your tutor to explain if you do not understand where the name comes from.
Input Voltage Unit - Position Sensor.Magnetic Switch Unit - Proximity Sensor.Switch Unit - Pressure Sensor.Rain Sensor - Moisture Sensor.
The Pulse Generator (15) can also be considered as an input device. It can provide square pulses whose period can be controlled using the variable resistor.
a. Connect up the following arrangement with the 4 mm socket in the 470nF line.
9 - 12VAC/DC
Power Supply Regulator
+
_
+
_ _
+
PulseGenerator
TransistorSwitch/Indicator
b. Switch on the power supply and observe the light emitting diode [LED] on the transistor switch/indicator unit. The LED comes on when the Pulse Generator is sending out a high signal.
c. Adjust the setting of the control knob on the Pulse Generator and note the effect.
Number of pulses per second increases as rotary control is turned clockwise
continuous pulses
Practical Work 1.2B: Investigating Output Drivers.
Activity 1a (For Alpha Kit Users):
a. Set up the following arrangement. Switch on the supply voltage.
9 - 12VAC/DC
Power Supply Regulator
+
_
+
_ _
+
Bulb Unit
b. Connect a 4 mm test lead to the Signal In socket of the bulb unit. This is the middle socket on the Alpha link.
c. Connect the other end of the test lead to the positive (+) line of the board (as shown by the solid line) and then to the negative (-) line (as shown by the dotted line).
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Topic 1.2 – Electronic Sub-Systems.
Activity 1b (For Control Studio Users):
a. Set up the following arrangement. Switch on the simulator, using the button.
b. Adjust the variable control on the input voltage unit, to investigate
what voltage is required at the input to the bulb unit to make the bulb light up.
Save your circuit as “E1-Systems-Circuit4”
Summary of Activity 1.
You should find that the function can be represented by the following table.
Unit Type ActionLamp Unit [30] Output Bulb lights up when signal
Use whichever system you have to investigate the other output devices and complete the table provided.
Unit Type Action
Lamp Unit [30] OutputBulb lights up when signal into board is LOW.
Buzzer Unit [31]Buzzer sounds when signal into board is ………………
Motor Unit [33]Motor turns up when signal into board is ………………
Solenoid Unit [34]
Solenoid activated when signal into board is ……………
We have now looked at a number of input and output units which are used to change input conditions into an electrical form, or change an electrical form into an output signal more suitable than an electrical voltage.
We are now in a position to change physical properties like light into electrical signals for processing, and electrical signals into physical outputs e.g. sound.
Later on in this topic we will look at the sub-systems needed to process the electrical signals to make the system do what we need it to do. First however we will look at a couple of basic system examples.
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Topic 1.2 – Electronic Sub-Systems.
Practical Work 1.2C: Setting up simple sensing systems.
Note: The power supply and the power supply regulator will not be shown on future block diagrams. They must however be included in any real system. All simulated systems will automatically insert the power supply but will not display it on screen. All exercises from here on will only show the Control Studio Solutions however it is possible to make all systems using Alpha / E&L etc.
Activity 1:
1a. Select, from your list of equipment, the units that you require to make up the system. Start with the Input Sensing Unit then the Output Driver and finally the Processing Unit.
Fill in their titles in the boxes provided below. Show clearly which are INPUT, PROCESSING and OUTPUT units.
A B
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PROBLEM 1: A system is required which activates a buzzer when light falls on a sensor.
1b. Set up the system in the control studio simulator with the rotary control knob on the light sensing unit about mid position. It should look like this:
Move the slider from dark to light and back again.
Describe what you observe and comment upon the effect that adjusting the
control knob, on the sensing unit, has upon the performance of the system.
1c. Now add two voltmeters to your circuit to measure the voltages at the output of the light sensor and of the transducer driver board to enable you to complete the following table. The circuit should look like this:
PROBLEM 2: A system is required which lights up a bulb when it gets dark.
A B C
Topic 1.2 – Electronic Sub-Systems.
Complete the following table:
VoltageA B C
LDR Covered
LDR Uncovered
Save your circuit as “E1-Systems-Circuit7”.
2c. It is possible to make the system work in this way without using an Inverting Unit. A careful study of the <Insert> - <Input> option will probably give the game away.
If you are certain of what to do try it out and explain what you did.If you are not sure, consult your tutor.
Another application for this type of circuit would be to control entry into a dark room. The bulb could be a warning light outside the door. When the lights are off in the room the bulb would serve as a warning for people not to enter.
Now it’s your turn - Try to design a control system to satisfy the following problem situations.
PROBLEM 3: A system is required which switches on a motor on a heater fan when the temperature falls below body temperature.
PROBLEM 4: A system is required which sounds a buzzer when a magnet passes a point.
PROBLEM 5: A system is required which switches on a lamp when it rains.
In each case you should:(a) decide upon which Input Units are required.(b) decide which Processing Units are required.(c) decide upon which Output Units are required.(d) draw a block diagram of the system.(e) set up the system and try it out.(f) make changes, if required, and draw a block diagram for your
final design.
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Topic 1.2 – Electronic Sub-Systems.
PROBLEM 3 - Solution.
(a) Input Sensing Unit -...........................................................................
(b) Processing Units -...........................................................................
(c) Output Unit -...........................................................................
(d) Block diagram.
(e) Test report...........................................................................................................
Once the input signals have been converted into an electrical form, by the Input Sensing Units, it is possible to use electronic subsystems to process the signals. The processed signal is then used to control Output devices.
The Processing Units available in each system can be divided up into three groups.
A brief description of the function of the signal processing units is provided with these notes. You will learn a lot more about them as you complete the next five assignments.
Drivers
The voltage signal coming out of most of the boards is incapable of providing enough current to drive output devices such as the motor unit.
The Transducer Driver and Transistor Switch units act as a switching buffer between the processing boards and the output units. The transistor switch unit can only switch on an output device which requires a small current. e.g, buzzer, lamp, or motor. The solenoid requires a much larger current and therefore a transducer driver must be used as this is capable of supplying several amps to the output device if required.
You will discover that both the output driving units have an inverting action i.e. if the voltage signal going into the board is HIGH, the signal coming out of the board is LOW.
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Topic 1.2 – Electronic Sub-Systems.
A driver must be connected between the signal coming out of the processing section and the output unit.
Input
Signal
InputSensor
SignalProcessing
OutputDriver Device
OutputOutput
Signal
In most cases the Transistor Switch Unit provides a cheaper alternative for the Transducer Driver Unit.
Logic Units
These units can be regarded as decision making units within electronic systems. They are digital processing units.
Digital devices are designed to operate on two voltage levels only. These are referred to as LOW and HIGH.
High
Low
Signal Level
If the voltage level is near to 0V (sometimes referred to as the 0V rail) it is called logic level 0.If the voltage level is near to the maximum positive supply (sometimes referred to the positive rail) it is called logic level 1.
The integrated circuit (IC) packages used in these systems are Complementary Metal Oxide Semiconductor (CMOS) types. They will operate on any voltage between +3 volt and +18 volts. Logic level 0 is any voltage less than 0.3 of the supply voltage while logic level 1 is a voltage greater than 0.7 of the supply voltage. CMOS IC’s are available in the 4000 series. The first number will be a '4' e.g. 4011.
V
0.7V
0.3V
0V
s
s
s
Logic Level 1
Logic Level 0
CMOS Logic Levels
Voltages between the logic level
bands should be avoided if possible. They cannot be identified by the IC’s.
Many types of logic gate are available but we concentrate on the following three types of logic gates. They are:
AND, OR, NOT gate (inverter)
The voltage signal out of a gate depends upon the logic level of signals into the gate. It will be near 0V or very near the positive supply voltage. The gates provided in your kit have two points where signals can enter the gates. These are usually referred to as A and B. The function of each gate is described in the following table.
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Topic 1.2 – Electronic Sub-Systems.
Unit Function Symbol
AND gateSignal out of a gate of logic level 1 if signals at A AND B are 1's.
OR gateSignal out of a gate of logic level 1 if signal at A OR B is 1.
NOT gate(Inverter)
Signal out is NOT a 1 (i.e. 0) if the signal in is a 1, and vice versa.
In the following assignments you will be asked several design problems which can be carried out either on Alpha / E&L or Control Studio which will enhance your understanding of the units and how they can be used to form simple systems.
If you are using a simulator and you have time you might want to try and build them using the real boards.
Practical Work 1.2D: Investigating the use of logic gates in systems.
INFORMATION:Logic gates are used when decisions have to be made by the system. The output device becomes operative when certain input signal conditions are met e.g. a motor only comes on when two input switches are pressed.
Activity 1:
1a. Set up the following system.
The signal from the switch units change from 0 V (low) to + 5 V (high)
when the buttons are pressed. To press both buttons hold the <Shift> key down when you click with the left mouse button.
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A
Topic 1.2 – Electronic Sub-Systems.
1b. Use your system to enable you to complete the following table.
Is Switch BPressed ?
Is Switch APressed ?
Is the OutputIndicator On ?
No NoNo YesYes NoYes Yes
Complete the following sentence:
The indicator is ON if switch A .........................................are pressed.
For convenience we can use the following convention to indicate the state of the signals.
1c. Complete the following table for the AND gate, using the convention above. The table will show the state of the signal coming out of the gate for all possible setting of the input switches.
Switch B Switch A Signal Out (Q)0 00 11 01 1
35
SIGNAL IN
If a switch is not pressed, the signal coming out is at 0V and its logic state is represented by a 0.
If a switch is pressed, the signal coming out is at +5V and its logic state is represented by a 1.
SIGNAL OUT
If the indicator is OFF the signal coming out of the gate is at 0V and its logic state is represented by 0.
If the indicator is ON the signal coming out of the gate is at +5V and its logic state is represented by 1.
A family, living out in the country, require a system that brings on an outside light when it gets dark. In order to test the lamp they would like a press switch fitted into the system which can also be used to switch on the lamp.
Which units are required as input sensors to the system ?
[b]...............................................................................................Which unit is required for the output unit ? ................................
The processing section has to light up the lamp when it gets dark OR if the switch is pressed.
Which units are required for the processing section ?
[b]...............................................................................................The following block diagram suggests a possible layout for the system. Label the blocks.
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Topic 1.2 – Electronic Sub-Systems.
Set up the system and try it out. Report on your findings...........................................................................................................
............................Save your final circuit as “E1-Systems-Circuit14”.
Design Problem 2
A system is required to switch on a warning light that can be placed on a rubbish skip to warn passing cars so that there isn’t an accident. The lamp should flash when it gets dark.
Follow the design procedure suggested in previous Assignment.
Units required : .......................................................................................................
Set up the system and try it out. Report on your findings...........................................................................................................
Set up the system and try it out. Report on your findings...........................................................................................................
Save your final circuit as “E1-Systems-Circuit16”.
Other useful units
Two other very useful units that are often used in electronic circuits are the Latch unit and the Delay Unit.
The Latch Unit.
The latch unit is used when you want to keep a signal on indefinitely until a reset button or signal is applied. For example you may have a temperature monitor on a freezer in a holiday caravan. If the power fails and the contents of the freezer defrost before the power is restored, a light could be triggered to indicate that the food has defrosted and should be thrown out. The system can then be reset when the freezer has been restocked.
Unit Type Action
Latch Unit Digital
Output stays on indefinitely in response to a trigger
The Delay unit, as its name suggests introduces a delay into the signal, which is of a predetermined duration. At the end of the set time the signal returns to its original state automatically. e.g. an external security light, triggered by the movement of an object, stays on for a couple of minutes before being switched off.
Unit Type Action
Delay Unit Digital
Output is delayed by a fixed period before going high in response to a trigger pulse.
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Input
OutputDelay
Topic 1.2 – Electronic Sub-Systems.
Practical Work 1.2E : Investigating the Latch Unit and Delay Unit
Activity 1:
1a. Set up the following system which is to serve as a burglar alarm. The buzzer sounds if the burglar cuts a light beam.
1b. Check that the system works. Note the effect of adjusting the rotary
.......................................................................................................................................2c. Add a switch unit to the system and link its output to the reset pin
on the Latch. Try resetting the system by using the extra switch.44
Topic 1.2 – Electronic Sub-Systems.
Which logic level is required to reset the system ?
Remember this, it will prove useful later on in this assignment.
Save your final circuit as “E1-Systems-Circuit18”.
Design Problem 4
A system is required to sound an alarm if your cat has gone out and switches it off when it returns. The cat enters and leaves the house through a cat flap.
N.B. It must only work for your cat.HINT: Your cat could carry something.
Units required : .......................................................................................................
Set up the system and try it out. Report on your findings...........................................................................................................
Save your final circuit as “E1-Systems-Circuit20”.
Activity 4 :
In Activity 2 you improved the burglar alarm from Activity 1 by using a latch. It is possible to use a delay instead of the latch, to provide an alternative solution to the alarm problem.
Set up the system and try it out. Report on your findings...........................................................................................................
This system is very sensitive, only slight changes in noise will affect the output. The comparator is used in situations where input voltages change very little, and it is necessary to actually catch those changes.
Save your final circuit as “E1-Systems-Circuit23”.
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Topic 1.2 – Electronic Sub-Systems.
Homework Questions 2.
Answer all questions in the spaces provided, continue on a separate piece of paper if required.
1. Describe the role of the Transducer Driver, or Transistor Switch as an output unit ?
9. You are provided with the following functional blocks.
Light Sensing Unit, Debounced Switch Unit, Temperature Sensing Unit, OR gate, AND gate, Pulse Generator Unit, Rain Sensor, Buzzer Unit, Lamp Unit, Transducer Driver.
a) Draw a block diagram showing how you would make a system that produces bleeps of sound if a door is opened.
[3]b) Draw another block diagram showing how you would modify
this system so that the bleeps were produced if a door was opened or a light beam was broken.
[2]
c) i) This system could be used for a burglar alarm, what extra unit would you need to ensure that the alarm stayed on once activated even if the burglar shut the doors after him ?
10. A market gardener wishes to install a system in her greenhouse that will open the ventilation grills automatically when the temperature of the air reaches a predetermined value. There must also be a manual override to the system.
a) Select electronic subsystems from the list below and design a solution to the market gardeners problem. Draw your solution as a block diagram in the space below. (You do not have to use all of the subsystems in the list)
Light Sensing Unit, Debounced Switch Unit, Temperature Sensing Unit, OR gate, AND gate, Pulse Generator Unit, Rain Sensor, Buzzer Unit, Lamp Unit, Transducer Driver, Inverter, Motor, Solenoid, Latch.
[3]b) Redesign the system so that the ventilation grill will only
operate in daylight.
[3]11. A control system is required to run an industrial boiler, it has the
following specification. A motor supplies oil to the boiler. If the boiler overheats or produces too much smoke it is to be cut off and an alarm sounded.
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Topic 1.2 – Electronic Sub-Systems.
a) Design a control system, using any of the following systems blocks.
Light Sensing Unit, Debounced Switch Unit, Temperature Sensing Unit, OR gate, AND gate, Pulse Generator Unit, Rain Sensor, Buzzer Unit, Lamp Unit, Transducer Driver, Inverter, Motor, Solenoid, Latch.
[7]
b) Having built the system it is found that with the boiler at normal temperature and no smoke being produced the pump does not run. However if the light sensor is covered the pump does run.
Output Unit =..........................................................................
[2]
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Topic 1.2 – Electronic Sub-Systems.
Solutions to Homework Questions.
Solutions to Homework Questions 1:
1. An analogue sensor is one which can provide as its output, a voltage signal which can have a value anywhere between 0V and the maximum voltage of the power supply. The output tends to change slowly with time.
2. A digital sensor is one which can provide as its output, a voltage signal which can have only two values 0V and the maximum voltage of the power supply. The output tends to change rapidly with time.
3. a) Any two from Switch Unit, Magnetic Switch Unit, Rain Sensor.
b) Any two from Light Sensing Unit, Temperature Sensing Unit, Input Voltage Unit.
c) Buzzer Unit.
4. a) The light sensing unit, uses light as its input and produces at its output a changing voltage signal which represents the amount of light shining onto the sensor. The unit is analogue and changes tend to take place slowly as the light intensity changes.
b) The lamp unit is an output device which takes an electrical signal and converts it into a visible indicator, that the electrical signal is present.
c) The temperature sensing unit uses temperature as its input and produces at its output a changing voltage signal which represents the temperature of the sensor. The unit is analogue and changes in output voltage tend to occur slowly as the temperature of the sensor varies.
d) The magnetic switch / reed unit is a digital input sensor which is a switch operated by a magnet. When the magnet is close to the switch the contacts close and complete the circuit. When no magnet is present the switch contacts are open.
1. The transducer driver or transistor switch is needed as an output device in order to boost the current available from the processing sections of electronic subsystems to drive high current loads like motors and solenoids.
2. a) OR Gate.
A B Q0 0 00 1 11 0 11 1 1
b) AND Gate.
A B Q0 0 00 1 01 0 01 1 1
3. The NOT gate or inverter, has just one input and one output. Its function is to invert or reverse the voltage level of the signal coming in to the gate. In other words if a logic ‘0’ is present at the input a logic ‘1’ will be present at the output. If a logic ‘1’ is present at the input then a logic ‘0’ will be present at the output.
4. The voltage comparator, compares two voltages and gives an output of full supply voltage when the input signal is bigger than the reference signal, and an output of 0V when the input voltage is smaller than the reference voltage.
5. The pulse generator unit gives and output which is constantly changing from 0 to maximum supply voltage and back to 0V without any input being present. It is used mainly to drive counter units and provide a signal capable of making a lamp flash on and off.
6. The Latch unit is very much like a memory unit. It will remember an event taking place, even if the event lasts only for a few tenths of a second. The unit will remain in its ‘on’ state until it is manually reset, or is reset by another electrical system. Its main use in applications like burglar alarms etc.
7. The delay unit as its name implies, delays an electrical signal for a fixed length of time. In other words short events can be made longer for example, an outside light which can be switched on as
60
Topic 1.2 – Electronic Sub-Systems.
you leave the house and it will remain on for long enough for you to lock the door before going off by itself.
8.
A
B
C TransducerDriver
BuzzerUnit
a) INPUT | PROCESSING | OUTPUT
b) i) A = Rain Sensor or Light sensor & &
ii) B = Light Sensor or Rain Sensor
iii) C = AND Gate
c) Warn someone who has washing on the line that it is raining.
ii) The latch would have to be connected between the output of the OR gate and the input to the AND gate so that once the light sensor output goes high or the door was opened the signal from the gate would be latched on, keeping the input to the AND gate high, and hence letting the pulse generator signal pass through to the buzzer and therefore keep the buzzer going until the latch was reset.
b) i) The light sensor is providing the inverse logic output to that required. e.g.. ‘0’ instead of ‘1’.
ii) 1. Turn light sensor board around.2. Add and inverter after the light sensor but before
the input to the OR gate.
c) Input Sensor = Needle / Stylus
Output Unit = Loudspeaker / Earphones
Now its time to look at some exam questions.
64
TransducerDriver
ORGate
LightSensor
Motor
TemperatureSensor
TransducerDriver
Inverter
Buzzer
Topic 1.2 – Electronic Sub-Systems.
Examination Style Questions:
1. Here is a list of electronic sub-systems:
latch motor light sensor tilt-switch
Add the correct sub-system to complete the following statements.
(a) A ................................ is an analogue input sub-system;
(b) A ................................ is a processing sub-system;
(c) A ................................ is an output sub-system. [3]
2. There are three types of electronic subsystem, known as Input, Process and Output.
Here are three subsystems:
Subsystem Type (Input, Process, or Output)
Lamp unit
Light Sensing Unit
Comparator
For each one, decide which type it is.Add the word Input, Process or Output to show what you have decided. [3]
3. Here is a system to warn someone that it is raining.
(a) Which one of the following is the best sub-system to use as block X ? A. Light sensing unitB. Temperature sensing unitC. Moisture sensing unitD. Pressure sensing unit Answer = ……….
[1](b) Which one of the following is the best sub-system to use as block Y ?
A. NOR gateB. CounterC. Time delayD. Transistor switch / transducer driver Answer = ……….
[1](c) Name a suitable sub-system for block Z ………………..
7. Here is part of a block diagram for a house alarm.The owner sets the alarm by turning a key operated switch.When someone then opens a window, a micro-switch operates and the alarm sounds.
(a) The following sub-systems are used in this alarm:
Key switch Transducer driver AND gate Micro-switch Buzzer
Which sub-system will be used for :
(i) block A? ....................................
(ii) block B? ....................................
(iii) Put an “X” on the diagram opposite to show where you would place this sub-system.
[1]
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Topic 1.2 – Electronic Sub-Systems.
Self Evaluation Review
Learning ObjectivesMy personal review of these objectives:
Use the following sub-systems as part of a block diagram;
Input units: light, temperature, rotation, magnetic, moisture, sound, pressure pad/switch, and pulse generator.Output devices: lamp, buzzer, motor, solenoid, and LED.Signal processing: inverter, AND gate, OR gate, latch, time delay and comparator.
State the function of a transducer driver.describe possible applications of an electronic system from a block diagram;produce a block diagram for a system to solve a given problem;design and test electronic systems.
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