Discrete State Control

1
Discrete State Control

• Introduction
• PLCs
• Web Tutorial
• Allen-Bradley Example
• Ladder logic to Boolean Algebra
• Ladder logic to AND/OR gates
• Example problem
• Ladder logic to C
• Ladder logic to truth table
• Web references
• Summary

2
Programmable Logic Controllers
http//www.plcs.net/contents.shtml
3
PLC Example
Ground Rail
011
006
007
Rung
1 2 3 4 5 6 7
Allen-Bradley SLC-100 Demo
008
901
CTU
5
901
012
007 is a normally closed switch.
008
902
006, 008, and 010 are Normally Open pushbuttons.
RTO
Hot Rail
5.0
902
013
011, 012, and 013 are 120 volt light bulbs
901
010
RST
901 is an up-counter 902 is a timer (seconds) RST
is a reset
010
902
RST
4
Ladder to Boolean Algebra
011
006
007
Rung
1 2 3 4 5 6 7
008
901
CTU
5
901
012
008
902
RTO
5.0
902
013
901
010
RST
010
902
RST
5
Ladder to Boolean II
X
A
B
D
C
Y
X
B
C
Z
Y
A
6
Ladder Logic to Gates
X
A
B
A
X
AND
B
X
A
A
B
X
OR
B
http//educ.queensu.ca/compsci/units/BoolLogic/su
mmary.html
7
Gates to Ladder Logic Problem
U
AND
V
OR
W
X
AND
Q
OR
Y
Z
8
Solution
CR1
V
U
W
CR2
X
Y
CR1
Q
CR2
Z
9
Figure 8-18 (7th Edition)
PB1
PB2
CR1
CR1
Latch
G
CR1
R
CR1
Ladder diagram to control two lights
10
C Program

• / PLC1 Simulation of Ladder diagram on previous
  slide/
• include ltstdio.hgt
• main ()
• while (pb2 ! -1)
• count
• if ((pb1 pb2) (cr1 pb2))
• cr1 1
• pb1 0
• else
• cr1 0
• pb2 1
• if (!cr1)
• g 1
• else
• g 0
• if (cr1)
• r 1
• else

11
Fig. 8.22 Pg-391 7th Ed.
PB4 PB3 PB2 PB1 M1-up M2-dn
0 0 0 0 0 0
0 0 0 1 0 1
0 0 1 0 0 0
0 0 1 1 0 0
0 1 0 0 1 0
0 1 0 1 0 0
0 1 1 0 0 0
0 1 1 1 0 0
1 0 0 0 0 1
1 0 0 1 0 1
1 0 1 0 0 0
1 0 1 1 0 0
1 1 0 0 0 0
1 1 0 1 0 0
1 1 1 0 0 0
1 1 1 1 0 0
12
For Reference

• Rockwell Automation/Allen-Bradley
• http//www.ab.com/
• Toshiba PLCs
• http//xtronics.com/toshiba/plc.htm
• Mitsubishi PLCs
• http//www.meau.com/eprise/main/Web_Site_Pages/Pub
  lic/Products/PLC/P-PLC-Family
• Keyence PLCs
• http//world.keyence.com/products/programmable_log
  ic_controllers/plc.html
• Open Source (Linux) PLCs
• http//www.puffinplc.org/
• Automation Direct (Koyo's DirectLOGIC
  programmable logic controllers)
• http//www.automation-direct.com/
• Mr. PLC (PLC Forum)
• http//www.mrplc.com/
• State Language for Machine Control
• State Language Paper

13
Summary

• Introduction
• PLCs
• Web Tutorial
• Allen-Bradley Example
• Ladder logic to Boolean Algebra
• Ladder logic to AND/OR gates
• Example problem
• Ladder logic to C
• Ladder logic to truth table
• Web references