Page 139 - Programmable Logic Controllers, Fifth Edition

Ladder logic program
Man/Auto Low sensor switch OFF/ON Motor
I:2/4 I:2/8 I:2/0 O:3/1
Man/Auto Latch/Unlatch

I:2/4 B3:0/0
Man/Auto High sensor switch Latch coil
L
I:2/4 I:2/12 B3:0/0
Man/Auto Low sensor switch Unlatch coil
U
I:2/4 I:2/8 B3:0/0
Man/Auto

Motor I:2/4 G

O:3/1 O:3/5
Low sensor switch R

I:2/8 O:3/9
High sensor switch Y

I:2/12 O:3/13
Slots
0 1 2 3 4 56
Power
supply

Input module Output module
0 4 8 12 24 VDC 0 4 8 12 240 VAC
1 5 9 13 16-point discrete Field device 1 5 9 13 16-point discrete
2 6 10 14 input module power supply 2 6 10 14 output module
3 7 11 15 L2 L1 3 7 11 15
240 VAC
OFF ON
IN 0 VAC
IN 1 Motor OUT 0
IN 2 M OUT 1
Man Auto IN 3 OUT 2
IN 4 Pump running OUT 3
IN 5 OUT 4
Low sensor IN 6 G OUT 5
switch IN 7 OUT 6
IN 8 Low level OUT 7
IN 9 OUT 8
High sensor IN 10 R OUT 9
switch IN 11 OUT 10
IN 12 OUT 11
IN 13 High level OUT 12
IN 14 Y OUT 13
DC IN 15 OUT 14
24 VDC COM OUT 15
AC
DC
+DC –DC COM COM
Field device
power supply
Figure 6-58 Water-level control program implemented using an Allen-Bradley modular SLC 500 controller.

120 Chapter 6 Developing Fundamental PLC Wiring Diagrams and Ladder Logic Programs

pet73842_ch06_098-130.indd 120 05/11/15 4:20 PM