FUNDAMENTOS DEL
CONTROLADOR
PROGRAMABLE
1
¿QUE ES UN
CONTROLADOR
PROGRAMABLE?
OUTPUTS
ENTRADAS
PROGRAMMABLE
CONTROLLER
CR
• A solid state device that controls output devices based on the status of
the inputs, and a user developed program.
• Originally developed to directly replace relays used for discrete control.
2
INPUT DEVICES
• Pushbuttons
• Selector Switches
• Limit Switches
• Level Switches
• Photoelectric Sensors
• Proximity Sensors
• Motor Starter Contacts
• 120 VAC
• 240 VAC
• 12 VDC
• 24 VAC/VDC
• TTL
• Relay Contacts
• Thumbwheel Switches
3
OUTPUT DEVICES
• Valves
• Motor Starters
• Solenoids
• Control Relays
Relays
• 120 VAC/VDC
• 240 VAC/VDC
• 24 VAC/VDC
• Alarms
Triac
• Lights
• 120 VAC
• Fans
MOSFET
• Horns
• 24 VDC
4
Inside a PLC
Communications
I
n
p
u
t
High
Voltage
Isolation
Barrier
C
i
r
c
u
i
t
s
Central
Processor
MEMORY
O
u
t
p
u
t
C
i
r
c
u
i
t
s
Isolation
Barrier
CR
High
Voltage
data
program
Low Voltage
AC Power Supply
85-264 VAC, 50/60Hz
or
DC Power Supply
5
PLC’s Come in a Variety of Sizes...

Micro
– Typically less than 32 I/O

Small
– Typically less than 128 I/O

Medium
– Typically less than 1024 I/O

Large
– Typically greater than 1024 I/O
6
And a variety of shapes/configurations

Packaged

Packaged with expansion

Modular (rack less)

Modular (rack based)

Distributed
7
Packaged PLC
Power supply, Inputs, Outputs and Communication port are enclosed in a single package.
INPUT and OUTPUT devices are wired individually to the packaged controller.
Motor
M1
O/3
OUTPUT
OOOO
OOOO
OOOO
Stop
INPUTS
I/Ø
I/1
Start
8
Packaged PLC with Expansion
Base is identical to the standard Packaged PLC, but it also has the ability to drive
additional I/O.
The most common form of expansion is a block of I/O that uses the same base, or makes
use of different types of expansion “modules”.
Connections between the base and the expansion device is either direct (mating
connector), or by using a wired approach (ribbon connector is very common).
OOOO
OOOO
OOOO
2 Slot Expansion
Chassis
9
Modular PLC’s
(The Ultimate in Flexibility)

Mix N Match Components
– Processors, Power Supplies and I/O are plugged into a rack or chassis
– Available in Small, Medium, and Large platforms
– Flexibility results in higher costs when compared to packaged

Modular PLC’s are either rack based or are rack-less

Allen-Bradley SLC-500 and PLC 5 are modular PLC’s
Processor RUN
indicator
Processor FLT
indicator
SLC 5/03 CPU
RUN
FORCE
FLT
DH485
BATT
RS232
RUN REM
PROG
Force I/O
indicator
DH-485 Port
status indicator
Battery status
indicator
RS-232 Port
status indicator
DH-485 Port
connection for
programming
terminal
Keyswitch
RUN, REM,
PROG
OUT 0
IN 0
RS-232 Port for
programming
terminal
Power Supply
Output Modules
10
Input Modules
Modular Rack-Less PLC’s
(The Ultimate in Flexibility)

Identical in functionality to rack based PLC’s

Typically not as robust (packaging)

Typically found on “smaller” (small and medium)
sized PLC’s.

Will likely become the prevalent form of packaging in
the future.
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Distributed

Rely on communications for EVERYTHING

All I/O is connected to the processor through a “High
Speed” data link.

Typically found on “larger” (medium and large)
PLC’s.

For certain applications this type of form factor is
very advantageous.

Usually higher cost for hardware, but much lower
cost for system integration.
12
Typical PLC Application
Motor
Solenoid 1
Solenoid 2
Ingredient A
Ingredient B
Sensor 1
Sensor 2
Solenoid 3
13
Operation of Mixer
(Defining the Outputs)
Solenoid 1
On = Sol 3 is off, and Motor is off, and Sensor 2 is
off, and Auto Switch is on
Off = Sol 3 is on, or Motor is on, or Sensor 2 is on
Solenoid 2
Motor
Solenoid 1
Solenoid 2
Ingredient
A
Ingredient
B
On = Sol 3 is off, and Motor is off, and Sensor 2 is on
Off = Sol 3 is on, or Motor is on, or Sensor 1 is on
Motor
Sensor 1
On = Sensor 1 is on, and Solenoid 2 is off, and
Solenoid 1 is off
Off = Solenoid 3 on
Sensor 2
Solenoid 3
Solenoid 3
On = Sol 1 is off, and Sol 2 is off, and Motor has run
for 30 sec.
Off = Solenoid 3 has been on for 60 sec.
14
Input Wiring
Isolation
Barrier
Terminal
Block
Input Devices
1
2
3
L1
L1
4
5
6
7
8
P
L
C
9
L2
10
COM
15
Output Wiring
Isolation
Barrier
CR
Terminal
Block
OUT 1
OUT 1
Output Devices
L1
L2
OUT 2
P
L
C
OUT 2
OUT 3
OUT 3
L1
L2
OUT 4
OUT 4
OUT 5
OUT 5
OUT 6
OUT 6
16
PLC Operating Cycle
START
Housekeeping
Input Scan
Program Scan
Communications
Output Scan
17
Ladder Logic Concepts
Read / Conditional
Instructions
Start (Rung #1)
||
()
||
||
Write / Control
Instruction
||
||
|/|
()
|/|
()
|/|
()
|/|
()
||
End (Rung #5)
||
18
Ladder Logic Concepts
Input Instructions
Output Instruction
||
|/|
()
T
T
T
Logical Continuity
||
|/|
()
T
F
F
No Logical Continuity
19
Logical AND Construction
IF input 004 AND input 005 have power
THEN energize output 0
I/4
I/5
O/0
||
||
()
Off
20
Logical AND Construction
IF input 4 AND input 5 have power
THEN energize output 0
I/4
I/5
O/0
||
||
()
T
T
T
On
Logical Continuity
21
Logical OR Construction
IF input 4 OR input 5 have power
THEN energize output 0
I/4
O/0
||
()
Off
I/5
||
22
Logical OR Construction
IF input 4 OR input 5 have power
THEN energize output 0
F
I/4 T
O/0 On
||
()
I/5
Logical Continuity
||
23
Logical OR Construction
IF input 4 OR input 5 have power
THEN energize output 0
I/4
T
O/0
||
On
()
Logical Continuity
I/5
F||
I/4
F
O/0 Off
||
I/5
()
Logical Continuity
T||
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Complex Construction
I/4
I/0
I/1
I/9
I/10 O/0
||
|/|
||
||
|| ()
I/5
I/1
I/7
I/8
||
|/|
|/|
|/|
I/2
I/3
||
||
I/11
I/1
|/|
||
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Input Instructions - XIC, XIO
INPUT
Input Push Button
The status of the instruction is
If the
data file
bit is
XIC
Examine if Closed
XIO
Examine if Open
-| |-
-|/|-
Logic 0
False
True
Logic 1
True
False
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Output Instruction - OTE
||
|/|
()
T
T
T
OTE
Output Energize
-( )-
Rung
State
Status
Bit
Output
Terminal
TRUE
ON
ENERGIZED
FALSE
OFF
De-energized
Output Pilot Light
OUTPUT
27
Putting it all Together
SLC 5/03 CPU
RUN
FLT
INPUT
OUTPUT
OUT 0
DH485
BATT
RUN
INPUT
FORCE
RS232
REM
PROG
IN 0
IN 0
OUT 0
||
()
28
Addressing Example
L1
PB1 LS1
L2
FS2
SOL6
L1
L2
I:1/1
I:1/2 I:1/3
||
DEVICE
ADDRESS
PB1
I:1/1
LS1
I:1/2
FS2
I:1/3
SOL6
O:3/1
||
||
O:3/1
()
29
Relay Logic to Ladder Logic
PB1
LS1
PB2
LS2
SOL2
CR3
LS3
I:1/1
I:1/2
O:3/0
||
||
()
I:1/3
I:1/4
B3/0
||
||
()
I:1/5
CR3
|/|
LS4
||
M1
B3/0
I:1/6
O:3/1
|/|
||
()
INPUT Address Assignment:
PB1- I:1/1
PB2- I:1/4
LS1- I:1/2
LS2- I:1/3
LS3- I:1/5
LS4- I:1/6
OUTPUT Address Assignment:
SOL2- O:3/0
M1- O:3/1
30
SOURCING vs. SINKING
The Mystery...
31
SOURCING vs. SINKING
DC I/O (General)
+VDC
+
DC
Power
Supply
DC COM
32
SOURCING vs. SINKING
DC I/O (General)
SOURCING Pushbutton
SINKING Pushbutton
+VDC
+
+
DC
Power
Supply
DC
Power
Supply
-
DC COM
33
SOURCING vs. SINKING
DC Inputs
Field
Device
+
IN1
DC
Input
Module
DC
Power
Supply
-
+VDC
DC COM
+
DC
Power
Supply
DC
Input
Module
Field
Device
IN1
34
SOURCING vs. SINKING
DC Outputs
+VDC
+VDC
OUT1
DC
Output
Module
+
Field
Device
DC
Output
Module
+
DC
Power
Supply
-
DC
Power
Supply
Field
Device
OUT1
DC COM
DC COM
35
RULES
F
Field devices on the positive side (+VDC) of the field power
supply are sourcing field devices.
F
Field devices on the negative side (DC COM) of the field
power supply are sinking field devices.
F
Sourcing field devices must be connected to sinking I/O cards
and vice versa.
F
Sinking field devices must be connected to sourcing I/O cards
and vice versa.
36