Automating Manufacturing Systems - Process Control and ...

plc pid - 25.10
Figure 25.10
A Combined System Model
A proportional control system can be implemented with the ladder logic shown in
Figure 25.11 and Figure 25.12. The first ladder logic sections setup and read the analog
input value, this is the feedback value.
S2:1/15 - first scan
MOV
Source 0000 0000 0000 0001
Dest N7:0
BT9:0/EN
BT9:1/EN
MOV
Source 0000 0101 0000 0000
Dest N7:2
BTW
Rack: 0
Group: 0
Module: 0
BT Array: BT9:0
Data File: N7:0
Length: 37
Continuous: no
BTR
Rack: 0
Group: 0
Module: 0
BT Array: BT9:1
Data File: N7:37
Length: 20
Continuous: no
Figure 25.11
Implementing a Proportional Controller with Ladder Logic
The control system has a start/stop button. When the system is active B3/0 will be
on, and the proportional controller calculation will be performed with the SUB and MUL
functions. When the system is inactive the MOV function will set the output to zero. The
last BTW function will continually output the calculated controller voltage.