1

 Goal:
 Introduction to electrical circuits, controls and preparing simple
electrical drawings.

2

 Discuss basic concepts for electrical circuits and controls.
 Learn how to read and create simple electrical drawings.

3

 Electrical drawings provide a complete description of the electrical
circuitry for a product.
 Circuit diagrams purpose is to clearly show how components are connected
electrically. This is not the
same as showing where components are physically, or how they have been
laid out on a circuit board.
 Standard symbols are used.

4


5


6


7


8


9


10


11

 Without doing any calculations, which light bulb has the lowest
resistance?
 75 W bulb at 120 V
 150 W bulb at 120 V

12

 Calculate the resistance using Power Law and Ohms Law. Use:
 I = P / V (P = VI)
& R = V / I
 North side of Table do 75 W bulb
 South side of Table do 150 W bulb
 Compare Results

13

 Voltage Law: The sum of the voltage rises around a closed loop in a
circuit must equal the sum of the voltage drops.
 Current Law: The sum of all currents into a junction (node) must equal
the sum of all currents flowing away from the junction.

14


15


16


17


18

 If each of the R’s were 60 W light bulbs, (R =240 ohm), what would be
the equivalent resistance for all three bulbs in parallel.
 What would be the total power draw for the three bulbs

19


20

 Simple Direct Control Systems can be place in two categories
 OpenLoop or Manual Systems
 Closed Loop or Automatic Systems

21


22


23

 Two Basic Configurations
 SERIES implies AND condition
 PARALLEL implies OR condition
 May Have combination SERIES/PARALLEL

24


25


26

 Threeway bulbs (like 50/100/150 W or 30/60/90 W) have only two
filaments (loads or resistors), how are they connected and how are they
switched?

27

 DWG 3  answer the questions pertaining to the drawings – Due Basics 5
 The material for drawing three follows the notes for this lecture in
your course material.

28


29

