Allen-Bradley SLC 500 Series User Manual

Publication 1747-RM001G-EN-P - November 2008
9-30 Proportional Integral Derivative Instruction
PID Rungstate
If the PID rung is false, the integral sum (words 17 and 18) is cleared and CV
remains in its last state.
Time Proportioning Outputs
For heating or cooling applications, the Control Variable analog output is
typically converted to a time-proportioning output. While this cannot be done
directly with the processor, you can use the program on the following page to
convert the Control Variable to a time proportioning output.
] [
N7:10
1
[OSR]
B3
0
( )
B3
3
MULTIPLY
Source A N7:0
Source B 16384
Dest N7:2
LIMIT TEST
Low Lim 0
Test N7:0
High Lim 100
FROM BCD
Source I1:1.0
Dest N7:0
DOUBLE DIVIDE
Source 100
Dest N7:8
] [
I:2.0
0
(U)
S:5
0
] [
I:2.0
1
] [
I:2.0
2
(L)
N7:10
1
(U)
N7:10
1
LIMIT TEST
Low Lim 101
Test N7:0
High Lim –1
FRD
LIM
LIM
DDV
MUL
Notes on Operation
A 3-digit BCD thumbwheel is wired to an input module at I1:1.0 (range
0-100).
A pushbutton wired to I1:2.0/0 accepts the thumbwheel value.
A selector switch for auto/manual mode is wired to I1:2.0/1 (auto) and
I1:2.0/2 (manual).
N7:0 stores the value entered on the thumbwheel switch.
N7:2 stores an intermediate calculation.
N7:8 is the PID control variable address.
N7:10 is the control block address of the PID instruction.
N7:26 Percent output is updated automatically by the PID instruction.

Allen-Bradley SLC 500 Series Specifications

General

Brand	Allen-Bradley
Model	SLC 500 Series
Category	Controller
Language	English