Chapter 9 Electrical Wiring Diagram Basics 209
Copyright Goodheart-Willcox Co., Inc.
1. Color all the lines connected to L1 one color, Figure 9-12A. Only wires
that are electrically the same L1 should be colored. Once an electrical
component, such as a switch or load, has been reached, the line stops.
2. Color all the lines connected to N a different color, Figure 9-12B.
The red and green color-coded lines now represent the rails of the
ladder, with the red line representing Line 1 on the left, and green
representing N on the right, Figure 9-12C.
3. Add the fi rst remaining, uncolored line, SW and R1 coil as the fi rst
rung of the ladder diagram. Each line segment that begins at one
color and ends at the other, is one rung on the ladder, Figure 9-12D.
4. Add the line with R1 contacts and an R2 coil to the second rung of
the ladder diagram.
5. Add the line with R2 contacts and an R3 coil to the third rung of the
ladder diagram.
6. Add the line with R3 contacts and the light bulb to the fi nal rung of
the ladder diagram.
By adding each of these rungs to the diagram, the completed ladder diagram
is created. From this completed diagram, it can be seen that the switch,
when closed, energizes the coil of relay 1. This causes the contacts of relay 1
to close, energizing the coil of relay 2. This causes the contacts of relay 2
to close, energizing the coil of relay 3. This causes the contacts of relay 3
to close, energizing the light bulb. Although the process of converting a
schematic diagram to a ladder diagram takes practice, the result is worth the
effort. Note that the order of rungs on the ladder diagram is not important.
9.2.5 Converting Schematic Diagrams to Ladder Diagrams
Not all equipment manufacturers provide ladder diagrams with their
equipment. However, a schematic diagram can be easily converted to a
ladder diagram for troubleshooting purposes.
Converting Schematic Diagrams
to Ladder Diagrams
One of the easiest ways to accomplish this is to use two different-color
highlighters to identify the power supply to the circuit. Consider the
schematic diagram in Figure 9-11.
Procedure
R1
R1
R2
R2
R3
R3
L1
N
SW
Goodheart-Willcox Publisher
Figure 9-11. An example of a schematic wiring diagram to be converted into a ladder diagram.
Copyright Goodheart-Willcox Co., Inc.
1. Color all the lines connected to L1 one color, Figure 9-12A. Only wires
that are electrically the same L1 should be colored. Once an electrical
component, such as a switch or load, has been reached, the line stops.
2. Color all the lines connected to N a different color, Figure 9-12B.
The red and green color-coded lines now represent the rails of the
ladder, with the red line representing Line 1 on the left, and green
representing N on the right, Figure 9-12C.
3. Add the fi rst remaining, uncolored line, SW and R1 coil as the fi rst
rung of the ladder diagram. Each line segment that begins at one
color and ends at the other, is one rung on the ladder, Figure 9-12D.
4. Add the line with R1 contacts and an R2 coil to the second rung of
the ladder diagram.
5. Add the line with R2 contacts and an R3 coil to the third rung of the
ladder diagram.
6. Add the line with R3 contacts and the light bulb to the fi nal rung of
the ladder diagram.
By adding each of these rungs to the diagram, the completed ladder diagram
is created. From this completed diagram, it can be seen that the switch,
when closed, energizes the coil of relay 1. This causes the contacts of relay 1
to close, energizing the coil of relay 2. This causes the contacts of relay 2
to close, energizing the coil of relay 3. This causes the contacts of relay 3
to close, energizing the light bulb. Although the process of converting a
schematic diagram to a ladder diagram takes practice, the result is worth the
effort. Note that the order of rungs on the ladder diagram is not important.
9.2.5 Converting Schematic Diagrams to Ladder Diagrams
Not all equipment manufacturers provide ladder diagrams with their
equipment. However, a schematic diagram can be easily converted to a
ladder diagram for troubleshooting purposes.
Converting Schematic Diagrams
to Ladder Diagrams
One of the easiest ways to accomplish this is to use two different-color
highlighters to identify the power supply to the circuit. Consider the
schematic diagram in Figure 9-11.
Procedure
R1
R1
R2
R2
R3
R3
L1
N
SW
Goodheart-Willcox Publisher
Figure 9-11. An example of a schematic wiring diagram to be converted into a ladder diagram.