Modular Electronics

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Modular Electronics

• Use the systems approach.
• Enables a structured approach to problem
  solving.
• Systems diagrams are used to provide a circuit
  overview.
• All electronic circuits have an input, a
  process and an output
• Identifying these basic parts is the first step
  towards a solution

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EL Modular System Boards
Although the CDT department has modular boards
and you will get the opportunity to use these, it
is much easier to use simulation software.
Therefore, for the majority of activities, you
will simulate rather than build boards.
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Analogue System Boards
An analogue signal varies according to the
physical surroundings. For example, the EL
light-sensing unit will send out a voltage that
is proportional to the amount of light falling on
the LDR.
Control Studio (Alpha) Boards
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Analogue Input Transducers

• Typical analogue input transducers are
• input voltage units
• light-sensing units
• temperate-sensing units
• moisture/rain sensor units
• sound-sensing units.

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Digital Input Transducers
A digital signal is one which has only two
settings, on or off. In electronic terms it has
only two levels, high or low.
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Digital Transducers

• Typical digital input transducers are
• switch units
• magnetic switch units
• pulse generator units.
• Logic on or high is Logic 1
• off or low is Logic 0.

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Output Transducers
Output transducers take an electrical signal and
change it into a physical output. They include
the output boards in modular systems or output
components in any electronic system.
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Pupil Activity Light Sensing

• Draw a block diagram of the system
• Draw a Systems diagram showing Input Process and
  Output stages
• Construct the circuit on Control Studio
• In your own words, explain what is happening

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Pupil Activity Light Sensing

• Draw a block diagram of the system
• Draw a Systems diagram showing Input Process and
  Output stages
• Construct the circuit on Control Studio
• In your own words, explain what is happening
• What does the inverter do?

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The Inverter OR NOT Gate
NOT Gate Symbol
Truth Table
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Pupil Activity

• Draw a block diagram of the system
• Draw a Systems diagram showing Input Process and
  Output stages
• Select suitable boards and construct the circuit
  in Control Studio
• In your own words, explain what is happening

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Pupil Asignment
A gardener needs a system which will detect when
the soil in his garden requires watering. Design
a system which will warn the gardener when he
should water his plants.

• Draw a block diagram for the new system.
• Draw a system diagram.
• Select suitable boards and construct your circuit
  in Control Studio.
• Name each of the boards used.
• Describe the operation of the circuit.

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Possible solution
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Pupil Assignment
Government legislation states that food should
be stored below 18 C. Design an electronic system
that will warn the freezer user if the
temperature rises above this preset level.
For the purposes of the simulation, the alarm
should sound if the temperature rises above
normal room temperature. The alarm should alert
the user even if they are not in the same room as
the freezer.

• Draw a system diagram to represent a suitable
  system.
• Draw a block diagram of a possible solution to
  the problem.
• Identify all sub-systems.
• Test your solution using modular boards.
• Explain how your system works.

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Pupil Activity

• An EL system is shown above,
• Draw a system diagram for the above system.
• Draw a block diagram of the system shown.
• Connect the sub-systems as shown.
• Make the power connection.
• Test out the operation of the system by pressing
  the switch.
• Explain what would happen if an inverter was
  added.
• State where the inverter would be positioned.

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AND Control

• Draw a system diagram for the system above.
• Draw a block diagram of the system shown.
• Connect the sub-systems as shown using Control
  Studio.
• Press switch A only.
• Press switch B only.
• Press both switches at the same time.
• Explain how the AND gate works.

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AND Gate
And Gate Symbol
Truth Table
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OR Control

• Draw a system diagram for the system above.
• Draw a block diagram of the system shown.
• Connect the sub-systems as shown using Control
  Studio.
• Press switch A only.
• Press switch B only.
• Press both switches at the same time.
• Explain how the OR gate works.

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OR Gate
OR Gate Symbol
OR Gate Truth Table
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Pupil Assignment
A washing machine manufacturer decides that to
improve efficiency the washing machine should not
start until two conditions have been met.

• The motor in the washing machine should only
  operate if
• The water is at the correct temperature.
• The water is at the correct level.
• Draw a system diagram to represent a suitable
  system.
• Draw a block diagram of a possible solution to
  the problem.
• Identify all sub-systems.
• Test your solution using modular boards or
  Control Studio.
• Explain how your system works.

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Solution
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Pupil Assignment
Automatic doors should open from both inside and
out. Design a simulation to solve this problem.
For this simulation a combination of light
sensors and switches can be used. A light sensor
should be used to open the doors from the
outside. A switch should be used to open the
doors from the inside. A solenoid unit should be
used to simulate the door mechanism.

• Draw a system diagram to represent a suitable
  system.
• Draw a block diagram of a possible solution to
  the problem.
• Identify all sub-systems.
• Test your solution using modular boards.
• Explain how your system works.

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Solution
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Pupil Activity (EL)

• Draw a system and block diagram for the system
  shown.
• Turn the potentiometer dial on the pulse
  generator fully clockwise.
• Record the output from the system.
• Turn the potentiometer dial on the pulse
  generator fully anticlockwise. Record the output
  from the system.
• Explain in your own words what the pulse
  generator does.
• Is the pulse generator
• ? an input transducer?
• ? an output transducer?
• ? a signal-processing device?

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Pupil Activity

• Using Control Studio,
• Copy the block diagram below
• Build the modular board system
• Describe in your own words what is happening

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Latch Unit

• Using EL or Control Studio
• Draw a block diagram for the system shown
• Build and test the system
• Describe in your own words what the latch unit
  does

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Latch Unit
A latched system is one that remains on until it
is reset. It is often called a memory system as
it remembers that the switch has been pressed
until the reset on the latch is pressed. Note
the inverter is needed because the latch unit
only works as the voltage signal is dropping
(EL) this is called negative-edge triggering.
The inverter allows the system to work when the
voltage signal is rising, as happens with a
normal switch unit. This converts the overall
system to positive-edge triggering.
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Pupil Assignment
Your Technological Studies room has an infrared
burglar alarm system fitted. The trouble is that
it sounds each time someone walks into the room.
Redesign the system so that it works in a more
acceptable fashion

• For the purpose of this simulation the alarm
  should sound if a light beam is broken.
• There should be a master switch in the janitors
  office.
• The alarm should not sound when the system is not
  set.
• Once set, the alarm should sound if the light
  beam is broken.
• The alarm should continue to sound even if the
  burglar leaves the room.
• The janitor should be able to reset the system
  when the police arrive.

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Relay Pupil Activity

• Draw a system diagram for the system shown
  below.
• Draw a block diagram of the system.
• Connect the sub-systems as shown.
• Press the switch unit and record what happens
  at the output.

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Relay Operation
The clicking sound at the output is caused by
the contacts of a switch inside the relay
closing. The contacts are moved by the
electromagnet energising.
A point that must be understood is that when the
relay contacts close, it provides no power to the
external circuit. To drive anything from a relay,
a separate power supply must be provided.
A relay is used to power a large current/voltage
device from a low current/voltage control circuit.
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Pupil Activity

• Draw a block diagram of the system shown below.
• Using EL, build and test the following system.
• In your own words describe what a relay is used
  for.

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Pupil Activity

• Draw a block diagram of the system shown
• Using Control Studio build the circuit
• Complete the truth table shown on the next
  slide

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Pupil Activity Continued
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Input/Output Unit
Draw block diagrams of both systems
This unit is used to connect external devices
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Pupil Activity

• Draw a block diagram of the system.
• Connect the sub-systems as shown.
• Adjust the potentiometer dial to the
  mid-position.
• Press the switch and hold. Note what happens.
• Try the same with the dial at different
  positions.
• Record the actual time delay for each position.

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Comparator

• Draw a block diagram of the system
• Using Control Studio build the circuit
• Try adjusting the comparator dial and observe
  what happens

The comparator compares a reference voltage to an
input voltage. If the input voltage is greater
than the reference voltage the comparator gives a
high signal out, (switches on buzzer).
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NAND NOR Boards