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Simple Electrical Circuits� and �Simulation

Dr. Neuhauser

Dr. Wakefield

12 November 2022

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What You Will Learn

  • Simple Electrical Circuits
  • Simple Electrical Components (batteries, lamps switches etc.)
  • How to interpret a design specification for a circuit
  • How to design the schematic for a circuit
  • How to simulate a circuit
  • How to build a circuit
  • How to verify a circuit

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Safety First, Last and Always

  • Nothing you can learn here is worth even a small injury
  • Be aware of what you are doing
  • Listen to your team assistant
  • If you are unsure about anything, ASK!

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What You Will Be Doing

  • You will be divided into teams of four or five engineers
  • Your team will have a supervisor whose job it is to make sure you are safe, answer your questions and give you hints.
  • You will be designing simple circuits using basic engineering processes
  • You will be working in steps with a limited set of components and building circuits to meet specific design objectives
  • As you progress you will receive more components to work with and more difficult designs.  How far you get will depend upon how well you work together as a team.

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Engineering

  • Engineering is the application of known principles to implement physical systems that meet a given specification
  • Today, engineered systems can be extremely complicated, so complicated that the old approach of using a drafting board, slide rule and tables of formula fall woefully short of getting the job done.
  • Instead, we must make use of sophisticated computer driven tools to test our designs before we build them.

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Complex Systems

  • CPU Chip – Apple M1 – 114 Billion Transistors
  • Aircraft Carrier – Nimitz Class – One billion parts
  • Space Shuttle – 2.5 Million moving parts
  • Automobile – Average car – 30,000
  • Cellphone – Apple iPhone 6 – about 3 Billion transistors

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What is a Circuit?

A circuit is a collection of electrical (or electronic) components connected by electrical conductors (usually “wires”).

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Why is it called a “Circuit”?

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What is an “Electrical Conductor”?

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What is the single most important characteristic of a Circuit?

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Just About the Simplest Circuit As You Can Imagine

Current Flow

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Controlling A Simple Circuit

Switch

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Knife Switch

http://www.learningaboutelectronics.com/Articles/Door-alarm-circuit.php

OPEN

No Current Flow

CLOSED

Current Flow

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Switch is OPEN – No Current Flow, No Light!

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Switch Closed – Current Flow, Light ON!

Do you recognize the function of this circuit? Do you have a circuit like this at home? In your car?

Current Flow

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Schematics

  • A schematic diagram or schematic is an abstract representation of physical circuit that shows only the essentials of the circuit and its function.
  • From the Greek skhēma – figure, appearance or nature of a thing.
  • Can you think of other visual abstractions in everyday life?

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The (Western) World’s Most Famous Abstraction??�(London Underground Map)

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What Is Missing from the Underground Map?

  • How far apart stations are
  • The distance between stations
  • Anything around the stations (except the river Thames)
  • Actual curves in the tracks (and the river!)

BUT…

  • It shows you what line your destination is on,
  • It shows you how to get there, and
  • It shows you when to get off!

Just what you need and no more!

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Electrical Schematic Diagrams

  • Shows you only the electrical components and their interconnection.
  • Physical devices, batteries, switches, lamps are shown by simple (more or less intuitive) symbols.
  • Placement of symbols and routing of wires usually do not show physical relationships, but rather are arranged for clarity of function.

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Real Life Circuit in Schematic Form

Maybe it works, but what a mess!

Ah! Much better!

Schematic built using Digi-Key Scheme-it!

https://www.digikey.com/schemeit/home/

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Some Schematic Symbols

+

This doesn’t look like a battery!

Looks like a lamp

Looks like a switch

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Series Circuits

A series circuit is one in which the same current flows through two or more elements.

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Parallel Circuits

A parallel circuit is one in which the current splits between two or more elements and then rejoins.

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Switch Zoo

SPST

SPDT

DPST

DPDT

P = Poles = The number independent circuits controlled

T= Throw = The number of selections for current flow

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Getting it Right!