This sample chapter is for review purposes only. Copyright © The Goodheart-Willcox Co., Inc. All rights reserved.
Chapter 5
Wiring Diagrams
Objectives
cable assembly
drawing
wire harness assembly
drawing
harness posts
flexible printed wiring
reference designation
component
representation
After studying this chapter, you will be able to:
•
Select wiring methods.
•
Create a wire list.
•
Draft a point-to-point diagram.
•
Draw a highway diagram.
•
Draw a cable assembly document.
•
Make a harness assembly drawing.
•
Select appropriate wire termination method.
Terms to Know
bus wire
spaghetti
point-to-point diagram
highway wiring
diagram
baseline diagram
interconnection
diagram
Wiring Methods
The majority of electronic equipment needs some kind of flexible wiring for
interconnections of systems. Understanding how to document this wiring is important
knowledge for the drafter. This chapter will cover the basic methods used.
There are many ways to show factory workers, service personnel, and others in
the engineering family how to wire electronics equipment. Normally the decision to
choose one method over another is based on three different things:
• Knowledge of the technician.
• Quantity to be built.
• Complexity of the equipment to be manufactured.
Schematic
The simplest method to get a wiring project built is to give a top qualified technician a schematic. The schematic will only supply the “from” and “to” information.
This information will describe where the wire will be hooked (the from position) and
where the wire is going (the to position). See Figure 5-1.
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Electronics Drafting
Figure 5-1.
A schematic being used to wire between components. Note 1: Technician runs wire connecting all the
switches. Note 2: Wire is run from the switch S1-2 to TB-1 (terminal block).
From a schematic, a drafter can create a wire list or other wiring documents. The
wiring list will save the technician time in reading the schematic.
Wire List
The wire list is another elementary document. It will include the information
from the schematic plus some additional information such as:
• Color of wire.
• Gage of wire.
• Length of wire.
• Entry in parts list.
• Condition at terminals.
Figure 5-2 shows how the wire list information is presented. To understand the
wire list information, you need to be familiar with wires and their terminations.
Wires or Conductors
Conductors used in wiring electronics equipment are either solid, stranded, or
flexible printed ribbon types of wiring. See Figure 5-3. Solid conductors have traditionally been used where they will not experience bending or flexing. They are less
expensive to manufacture so they cost less than stranded wiring. Because they
cannot be repeatedly flexed, they have limited areas of use. Solid wiring is used to
connect the outlets and switches in our houses. In electronics, solid wiring is used
mainly for jumpers (bus wiring) and for wire wrapping.
Wire
No.
1
2
3
4
5
6
7
1
Column
Column
Column
Column
Column
Column
Column
Column
Column
1
2
3
4
5
6
7
8
9
Size
Awg.
22
22
20
20
18
18
16
Item
No.
1
2
3
4
5
10
6
Color
R
W
O
Y
BK
BR
Y
From
XA1-22
XA1-21
XA1-19
XA1-18
XQ1-A
XQ1-B
XQ1-C
Wire List
Condition
Solder
Solder
Solder
Solder
Solder
Solder
Solder
A
Parts List
Condition
#6 Lug
#6 Lug
#6 Lug
Solder
Solder
Solder
Solder
9
Length
20
14
16
14
12
8
10
Chapter 5 Wiring Diagrams
To
EOT-2
PI-6
P2-20
S3-8
S3-7
TB1-1
TB1-2
8
Qty
36″
18″
12″
15″
11″
10″
Description
Awg red stranded teflon coated
Awg wht stranded teflon coated
Orn stranded teflon coated
Blu stranded teflon coated
Brn stranded teflon coated
Blk stranded teflon coated
Wire
Wire
Wire
Wire
Wire
Wire
8
A/R
B
Lug #6 Crimp
Solder 40/60
#22
#22
#22
#22
#22
#22
2
3
4
5
6
7
The wires position in the wire list
The size of the wire as it relates to the American Wire Gage Standard
The item number in the parts list where a complete description is given
The color of the wire
Terminal the wire is coming from
How that wire is connected to the terminal
Terminal the wire is going to
How the wire is connected to the terminal
Length of the wire between terminals
Item
No.
1
2
3
4
5
6
7
8
9
85
Figure 5-2.
A—The top section shows a wire list with typical information and below it is an explanation of the information
in each column. B—This parts list is used to purchase items listed in the third column in the wire list above.
Stranded wiring has superior handling and flexing qualities. This makes it the
most universally used wire. See Figure 5-4. The endurance of the stranded wire is
judged by the number of strands it contains. The larger the number of strands, the
greater its bending endurance.
The diameter of a wire is determined by its gage, which is determined by the
American Wire Gage Standard. See Figure 5-5. Stranded wire will be identified by
two numbers. The first number states the number of strands in the wire. The second
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Electronics Drafting
Figure 5-3.
A—Solid wire used where the
wire will not be flexed.
B—Stranded wire is used where
flexibility is needed. C—Flexible
ribbon cabling, used to connect
components inside your
computer.
Figure 5-4.
A table termination on a circuit
board saves space on the board.
The flexible mounting and
stranded wire help reduce stress
on the board and connector.
A
C
B
number states the gage of each strand. For example, 7/26 means 7 strands of
number #26 AWG wire, which is .0159” in diameter. The wire gage goes from #4/0
(the largest commonly used wire) to #44 (the smallest commonly used wire). The
table shown in Figure 5-5 has only given the even sizes. It also has been condensed
to show the most used wire sizes.
Wire length and diameter affect both the resistance and current-carrying ability.
The smaller diameter wires have more resistance to electron flow, and therefore less
capability to carry current load. See Figure 5-6.
Bus Wire
Bus wire is solid wire without insulation (bare) normally used to make short
terminal-to-terminal connections. It will be used where bending does not take place
after installation. Where the bus wire requires insulation a tube-type insulation
called spaghetti is slid over it. The reason for using spaghetti is to avoid having to
strip both ends of a short wire.
Figure 5-5.
The American Wire Gage table.
The table is condensed for this
example.
Figure 5-6.
Current ranges for wires.
Military Standards allow only
60% of these current values.
Shielded and Coaxial Cables
Awg.
Size
10
12
14
16
18
20
22
24
26
28
Chapter 5 Wiring Diagrams
Weight
Lbs/1000Ft
31.43
19.77
12.43
7.818
4.917
3.092
1.945
1.223
.7692
.4837
.031
.080
.203
.513
1.296
3.280
8.290
20.900
52.900
133.900
Ohms per
Lb.
Area Sq.
In.
.008155
.00513
.00323
.00203
.00128
.000804
.000503
.00317
.000199
.000125
American Wire Gage
Maximum
Current
Amperes
Area C/R
Mils
10,380
6,530
4,110
2,580
1,620
1,020
640
404
253
159
Wire Size
Awg.
50
40
30
20
15
11
9
5
2
.5
Diameter
Inches
.1019
.0808
.0641
.0508
.0403
.0320
.0250
.0201
.0159
.0126
10
12
14
16
18
20
22
24
26
28
Shielded and coaxial wires are used to exclude or contain undesirable radiation.
See Figure 5-7. An example for the use of a coaxial wire is in an automobile radio
antenna system. The shield around the signal wire keeps the unwanted engine and
electrical noise from radiating into the signal wire. Without this shield, we would
hear many interfering noises from engine electrical sources. The shield of the coaxial
cable is grounded so the interfering electrical energy or radiation will be absorbed
and sent to the chassis instead of the radio.
Wire Termination
In order to make a wire useful, we must be able to electrically secure it where
we desire. There are three basic ways to secure or terminate wires: soldering,
crimping, and wrapping. The method used is dictated by the terminal to which the
wire is to be secured. You can show the method on your drawing by techniques as
shown in Figure 5-8.
Wrapping is done by a special wire-wrapping tool. Large wire-wrapping projects will be done by an automated wrapping machine. The wrapping tools strip the
wire’s insulation and then wrap the wire tightly around the wrapping post. See
Figure 5-9. Wire wrapping has an economical advantage over soldering and crimp
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Electronics Drafting
A
Neoprene
insulation
Figure 5-7.
A—Coaxial cable. B—Multiple-conductor shielded cable.
Symbol
A
B
C
Copper
shield
Foil
B
Physical Part
Rubber
insulation
Conductor
Figure 5-8.
A—Solder terminal symbol and wire represented after it has been stripped for soldering. B—Lug crimped to
the end of a stripped wire. C—Spade lug.
Wrapping
post
Wrapped
wire
Figure 5-9.
A square wire wrapping post with a wire wrapped around it. The wire is stripped and wrapped tightly
around the post making a good electrical connection.
Chapter 5 Wiring Diagrams
terminations. Wrapping can be set up much easier for automated machines. Wire
used for wrapping is solid wire. The gages for this wiring method range from #20 to
#32 AWG.
Point-to-Point Wiring Diagrams
A point-to-point diagram is used to show the engineering, manufacturing, and
service personnel the wiring between and across components. See Figure 5-10.
Point-to-point diagrams contain the information necessary to make or follow all
wire connections. This wiring diagram can be shown on the assembly drawing. The
diagram on the assembly will be included only if it is practical, and if room is available.
The point-to-point drawing will not have a parts list. All the necessary items will be
called out on the assembly document.
Some point-to-point diagrams show wiring paths on a background of components
which are not drawn to scale. The components are drawn out of scale to fit the
requirements of a very complex wiring diagram. The wiring is easier to follow when
wires are on equal spacing. A second drawing method is to show the components
drawn to the true scale.
Point-to-point diagrams show the general physical arrangement of the component
parts. See Figure 5-11. General rules for wiring diagrams are as follows:
• Minimize jogs in lines.
• Run lines with a minimum of crosses.
• Space lines a minimum of 1/4” apart.
Figure 5-10.
A complex industrial point-to-point drawing.
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Electronics Drafting
Figure 5-11.
A correctly drawn point-to-point
wiring diagram. Note the
misnumbering of TB1 and S1 to
keep from crossing and jogging.
This is a good practice.
• Separate every three of four lines with an extra wide spacing when groups
of lines run parallel to each other. This helps the reader’s eye follow the individual lines.
• Label component on the right side. This will help the reader when searching
over a large drawing to find a specific component.
• Letter the components with larger bold letters. Use smaller lettering for
internal terminals.
• Component numbering will follow the location and identification given to it
when mounted in chassis.
Pictorial Point-to-Point Drawing
T1
Red
TB1
Yellow
White
Occasionally when there is a simple point-to-point drawing to be made, it can
often be drawn as a pictorial. Figure 5-12 is a good example of a pictorial point-topoint drawing. However, pictorials should only be attempted when there are only a
small number of wires and simple chassis layouts.
Figure 5-12.
A typical pictorial point-to-point
drawing.
Black
AC input
Highway Wiring Diagrams
Chapter 5 Wiring Diagrams
Highway wiring diagrams group the wires together into major paths called
highways. See Figure 5-13. The technique allows you to put many wires on a drawing
because this organized method saves room. The drawing shows the physical
arrangement of the component parts as we did in the point-to-point. It will be
possible to tell each wire’s destination, color, and gage by looking at either of its ends.
In Figure 5-13D we see a second method for showing highways. Note that some
companies apply a number to each wire and then create a separate table. The wire
number in the table will supply destination, color, and gage.
Baseline Diagrams
Baseline diagrams are like highway diagrams in that they can handle many
wires in an organized manner and they bundle the wires together in one main line.
See Figure 5-14. They also have a couple of differences. One is the placement of
components. The highway diagram is very concerned with physical placement of
the components. The baseline diagram just lines them up in a straight line.
Another difference is in the way the wires enter the main bundle. The highway
diagram shows which way the wire will be running in the bundle. The baseline
shows wires going 90° into the bundle without disclosing direction. The method for
drawing baseline diagrams is to:
• Add a construction line across the middle of the paper.
• Line up the components on either side of the line.
• Take short lines from each component and run them into the center line at 90°.
• Identify the wire destination and color.
• Make the center line a dark bold line.
A
B
C
Baseline drawings are used mostly for service manuals and maintenance books.
They are especially good for this kind of information because they can neatly show
many lines on a book-size sheet of paper. These drawings will not normally be used
for assembly work because the information is too limited.
Figure 5-13.
A—Typical highway diagram.
This method can handle many
wires in an organized manner.
B and C—Two methods for
routing individual wires into the
highway. They both show direction of travel. D—An alternate
method for highway diagrams. It
uses a table to inform the technician as to where each wire is
coming from and where it is
going. It also lists the wire’s
colors and gage.
D
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Electronics Drafting
Figure 5-14.
A baseline diagram showing another method of controlling many wires in an organized manner.
Interconnection Diagrams
Interconnection diagrams show the wiring between different electronic units
and between subassemblies. See Figure 5-15. This document is similar to the pointto-point wiring diagram. Each cable assembly and electronic unit is called out and
assigned a title and drawing number. Note the subassemblies are shown in phantom
lines. Internal connections of electronic units are not shown.
Cable Assembly Drawings
Cable assembly drawings are assembly drawings that contain all the necessary
information to manufacture a finished cable. See Figure 5-16. A cable assembly
drawing includes the following information:
• A complete parts list.
• A drawing showing all components.
• Reference designations for each component.
• A wiring diagram most often is part of the drawing. It will show the internal
wires in the cable.
• A general note section that will guide the assembler through the assembly.
Wire (Cable) Harness Assembly Drawings
Wire (cable) harness assembly drawings are the only wiring drawings drawn to
exact scale. See Figure 5-17. It is drawn to scale because it is not just a drawing, but
it is also a tool. This tool is used in manufacturing so that many identical parts can
be created. Harness drawings will be supported by a wiring list and parts list. It is
an assembly so it will need to be supplemented with all information needed by the
assembler. The benefits of this drawing are as follows:
Chapter 5 Wiring Diagrams
Figure 5-15.
A typical interconnection diagram. This is an assembly drawing and will require a parts list. Subassemblies
on an interconnection diagram are shown in phantom lines.
Figure 5-16.
A cable assembly and a schematic of its wires.
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Electronics Drafting
Harness above
routing board
A
Drawing on harness board.
Drawing shows routing.
B
It will support high volume manufacturing.
It will not require high priced technicians.
Quality control of the wiring is easier.
The wire installation is less expensive than installing many separate wires.
Figure 5-17.
A—Harness being removed from
the harness routing board.
B—The harness shown installed
in equipment.
•
•
•
•
Before we can begin a harness drawing, we must know the exact placement of
all the electrical components to be hooked up. The layout of the drawing and the
routing of the harness will be decided by studying this arrangement. See Figure 5-18.
Once we know where the harness will run, we can plan the layout on the drawing.
Routing of the wires in a harness is accomplished by retaining them between
harness posts. See Figure 5-19. Harness posts will be driven into a routing board as
the drawing directs. Harness posts will also be used as securing posts for each end
of the wire. The wire will be wrapped around the starting post. Once secured, it will
be run through the routing posts as described by the wire list. After routing, it will
be secured around an ending post or in a clip used for securing wires.
Lacing or cable straps will be used to hold the wires together once they are
routed. See Figure 5-20. Lacing or strapping will hold the bundle into a permanent
unit. Once the wires have been permanently bundled, they can then be lifted up off
the routing board. After a harness has been removed, another duplicate harness may
be started.
Cable strap
Figure 5-18.
Terminal Block 1 needs to be
wired. The right view shows
how the wiring will be routed to
service TB1. This is to provide a
service loop so the wires can be
easily hooked and unhooked.
Break-out
point
A
B
Component to
be Wired
Harness post
Chapter 5 Wiring Diagrams
Layout of Harness
to Service TB1
C
Figure 5-19.
A—Wiring being routed through harness posts. B—Picture of a wiring harness being automatically routed.
C—Example of a completed wiring harness. (Amphenol North America Division, Bunker Ramo Corp.)
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Electronics Drafting
Figure 5-20.
An example of lacing to keep the
wire bundle in the desired shape.
Lacing around harness
half-loop knots on bottom
After the harness has been manufactured, it will go to a higher assembly level where
it will be installed. In order to make the installation easier, we identify each wire in the
bundle. There are three methods of identifying wires. See Figure 5-21. The three methods
are: color, number, or destination. When using colors, each wire carrying a different
electronic signal will have a different color. Numbered wires will be numbered on
both ends with the same number tag. A wire identified by destination will have the
exact place where it is to be terminated tagged right on its ends. The destination
method will eliminate the need for a wire list during installation. Numbered or
colored wires must have a wire list with the harness in order to complete installations.
Flexible Printed Wiring
Whenever it is possible to automate, a process industry chooses that method.
Flexible printed wiring allows the wiring to be etched on thin film that can be
shaped to fit into the mechanical package. See Figure 5-22. A flexible circuit can be
mass-produced very inexpensively.
Typical Notes Used on Wiring Diagrams
Wire list will
state red wire
to TB1-1 & etc
Blue
Red
Yellow
Green
S1
TB1
TB1
There are notes that are used often for wiring diagrams. Examples of these notes
are as follows:
• This drawing used with:
Assembly drawing _____
Schematic drawing _____
Wiring diagram _____
Wire lengths determined by prototype.
Wire color coding per MIL-STD-681.
Wiring must conform to _____.
Soldering will conform to _____.
Unless otherwise specified, all wires are _____.
Lace harness at each breakout point and every _____” in-between.
Apply cable straps at each breakout point and every _____” in-between.
•
•
•
•
•
•
•
Figure 5-21.
Three ways to identify wires to
aid in the harness installation.
Wire list will
state No. 3 wire
goes to TB1-2
Wire itself is
marked to its
destination
Figure 5-22.
Flexible printed circuitry is being
used in place of having many loose
wires. It is used in assemblies
where many units will be
manufactured.
Reference Designations
Chapter 5 Wiring Diagrams
Reference designations are identical to those on the schematic except for component
sockets which are prefixed “X”. See Figure 5-23.
Component Representation
XQ1
Q1
Simplified View
Showing Polarity
Socket "XU1"
Component "U1"
Component representation is just a physical outline suggestive of the component’s
features. See Figure 5-24. This is meant to be a simplified view as seen from the
wiring side.
Figure 5-23.
Components and sockets and
their reference designations. X is
used to indicate the socket for
the component.
Figure 5-24.
The actual component, left, and
its representation on the right.
Note: Pins have been assigned
numbers. This is to help the technician during wire installation.
Wiring Side
Note: Polarity
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Electronics Drafting
Terminal Identification
E
Transistor
Emitter
Base
Collector
Battery
Anode
Cathode
Diode
Each terminal must be identified. Most components and connectors are marked
adequately, but if not, sufficient details must be supplied with a wiring diagram.
Leads of components, such as transistors, diode, electrolytic capacitor, batteries, and other
devices shall have their terminals identified or polarity marked, as in Figure 5-25.
Figure 5-25.
Polarized components with their
leads or polarity identified.
B
C
Review Questions
1. What three things are considered when choosing a wiring method?
2. What information is normally included in the wiring list?
3. Name two types of wiring.
4. What is the advantage of stranded wiring?
5. What does 7/26 mean when we relate it to wiring?
a. 7 strands wrapped around 26.
b. 7 gage wire wrapped by 26 gage wire.
c. 7 strands of 26 gage wire.
d. 7 strands that total 26 circular mills.
6. Gage of wire is determined by the _____ standard.
7. What is affected by wire length and diameter?
8. How do we use bus wire?
9. Shielded or _____ cable reduces interfering radiation.
10. A point-to-point diagram shows the physical arrangement of the components.
What other information does it convey?
11. When would we use pictorial point-to-point diagrams?
12. What is the advantage of a highway diagram?
13. Cable assembly drawings will contain what information?
14. Why is the cable harness assembly drawn to scale?
15. What are the advantages of cable harnesses?
16. How are harness posts used?
17. Cable straps or lacing serve what function?
18. What determines the type of termination a wire will make?
19. The most economical termination method with automation is _____(soldering,
crimping, or wrapping).
20. Subassemblies on _____ diagrams are shown in phantom lines.
Activities
Chapter 5 Wiring Diagrams
1. Using the test simulator schematic shown as Figure A, create a wiring list and
parts list. Wiring between the printed circuit connectors, switches, test points,
and connector need to be listed. For wire list format, refer to Figure 5-2. Wiring
shorting the switch (S4-B) has been accomplished in a subassembly, so do not list.
μ
Figure A.
Shown are the connections from the circuit board to the switches, connecctors, and test points.
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Electronics Drafting
2. Draft a point-to-point wiring diagram for Figure B, the test simulator. Check
Figure C for component numbering and sizes. Figure D will show panel
mounting positions. Use the wiring list generated in Activity 1 in this chapter
to aid in this solution. If the wiring list was not complete, use the information
indicated in Activity 1. All wire lengths determined at assembly. Note: Wiring
is installed with panel turned upside down. See Figure E.
Figure B.
An exploded view of a test simulator package. This is the final Assembly Drawing. Use this drawing to see
how the components are arranged. The arrangement is needed when working on the chapter activities. Note
the wiring will be done on the underside of the lid so turn it over so your drawing complements what the
wire installer sees.
Chapter 5 Wiring Diagrams
101
Figure C.
These components used in the test simulator project are important for planning the case mounting hardware.
The chapter activities refer several times to this Figure.
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Electronics Drafting
Figure D.
The front panel of the test simulator. The switch, test point, and circuit board positions are dimensionally
located. Switch information and position settings are silk-screened on the panel. The circuit board is shown in
phantom as it sits below the panel. Some of this information is needed in several other chapter problems.
Figure E.
This is the basic layout of the highway diagram for the test simulator. Complete this highway diagram using
wire destinations given on the schematic.
3. Create a highway diagram using information described in Activities 1 and 2.
Figure E shows the layout paths for the highway. Use as much information as
you can from previous activities.
4. Using all the accumulated information from previous activities, create a wiring
harness drawing. Note: This drawing is drafted to a 1=1 scale. It will be a tool
for manufacturing. Check Figures A, B, C, and D.
5. Draft a baseline diagram of the test simulator. Use baseline diagram in
Figure 5-14 as an example. Assign a color to each wire.
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