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

E&L 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.

Analogue System Boards An analogue signal varies according to the physical surroundings. For example, the E&L light-sensing unit will send out a voltage that is proportional to the amount of light falling on the LDR. Control Studio (Alpha) Boards

Analogue Input Transducers Typical analogue input transducers are: input voltage units light-sensing units temperate-sensing units moisture/rain sensor units sound-sensing units.

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.

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.

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.

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

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?

The Inverter OR NOT Gate Input Signal Output Signal 1 NOT Gate Symbol Truth Table

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

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.

Possible solution

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.

Pupil Activity An E&L 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.

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.

AND Gate Input A Input B Output 1 And Gate Symbol Truth Table

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.

OR Gate Input A Input B Output 1 OR Gate Symbol OR Gate Truth Table

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.

Solution

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.

Solution

Pupil Activity (E&L) 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?

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

Latch Unit Using E&L 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

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 (E&L) – 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.

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 janitor’s 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.

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.

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.

Pupil Activity Draw a block diagram of the system shown below. Using E&L, build and test the following system. In your own words describe what a relay is used for.

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

Pupil Activity Continued Magnetic switch Light sensor Push switch Bulb 1

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

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. Position Delay Fully clockwise Mid-position Full anti-clockwise

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).

NAND & NOR Boards