Systems Approach and Switches

Overview

This short lesson covers two separate but connected short topics. A systems approach to electronics considers circuits in terms of sub-systems and how these are connected. A systems approach simplifies the initial design of an electronic system and is easier to discuss and explain. Projects always start with a system diagram and a systems approach is a good way to design none trivial electronic circuits. Switches are included in this lesson as they are relevant at this point.

Learning Objectives

• Recognise that electronic systems are assembled from sensing (input), processing and output sub-systems, including:
• sensing (input) devices: light, temperature, magnetic field, pressure, moisture, sound, rotation
• signal processing: individual logic gates, latch, time delay, comparator
• output devices: lamp, buzzer, solenoid, LED, actuator (servo), motor, loudspeaker


• Use photosensitive devices, ntc thermistors, pressure, moisture and sound sensors, switches, potentiometers
• Design and test sensing circuits using these components by incorporating them into voltage dividers
• State the need for transducer drivers for some output devices


• Design and test electronic systems from written specifications
• Design and use switches and pull-up or pull-down resistors to provide correct logic level/edge triggered signals for logic gates and timing circuits

Lesson Content

Reading: Read all the sections of the webpage about system diagrams. This is a very short and concise webpage. Make notes about the different inputs, processes and outputs.

Reading: Read about all the different types of switches. Make notes about the different switches and their functions. Pay attention to the section about pull-up and pull-down resistors.

Lesson Review

Review your learning by working through the presentations or notes which summarise the website content.

Presentation: Powerpoint download. System diagrams explained.

Notes: PDF download. The website text reformatted as notes.

Presentation: Powerpoint download. All the different switches described and their different functions explained.

Notes: PDF download. The website in the form of notes.

Self Assessment

Complete either the questions (pdf download) OR the on-line quiz. They are the same questions.

Questions: PDF download. Questions about system diagrams and switches.

Quiz: On-line quiz about system diagrams and switches.

Self Evaluation

I can:

• Identify sub-systems as either input, process or output sub-systems
• Give examples of different input transducers
• Appreciate that some input transducers are used as part of a potential divider circuit
• Give examples of different process sub-systems
• Give examples of different output transducers
• Understand why some output transducers need to be used with a transducer driver
• Recall that bipolar transistors, MOSFETs or relays can be used as transducer drivers
• Appreciate that electronic systems need a power supply
• Use a written specification to draw the corresponding system diagram
• Describe the operation of a circuit from a system diagram
• Understand the operation of different types of switches
• Use the appropriate switch for a given operation
• Appreciate the switches usually need a pull-up or pull-down resistor to ensure reliable operation