plc
DESCRIPTION
basicsTRANSCRIPT
Main Parts of a PLC
Power SupplyCPU (Central Processing Unit)I/O (Input/Output)Indicator lightsPLC Forms
RackMiniShoeboxMicroSoftware
Chapter - PLC Wiring
Input Types
Proximity SwitchesSwitchesPotentiometerLVDTs
Voltages
12-24 Vdc100-120 Vac10-60 Vdc12-24 Vac/dc5 Vdc (TTL)200-240 Vac48 Vdc24 Vac
Input CardExample 2 4 V A C
P o w e rS up p ly
no rm a lly o p e n p ush- b utto n
no rm a lly o p e nte m p e ra ture sw itc h
P L C Inp ut C a rd2 4 V A C
it is in ra c k "b o b "s lo t 3
0 0
0 1
0 2
0 3
0 4
0 5
0 6
0 7
P ushb utto n (b o b :3 :I.D a ta .1 )
Te m p se nso r (b o b :3 :I.D a ta .3 )
C O M
N o te : inp uts a re no rm a lly high im p e d a nc e . T his m e a ns tha t the y w illuse ve ry little c urre nt.
H o t
N e ut.
Output Types
Solenoid ValvesLightsMotor StartersServo Motors
Output Voltages
120 Vac24 Vdc12-48 Vac12-48 Vdc5Vdc (TTL)230 Vac
Output CardExample(Transistors)
2 4 V D CO utp ut C a rd
ra c k "sue "s lo t 2
C O M
0 0
0 1
0 2
0 3
0 4
0 5
0 6
0 7
2 4 V L a m p
R e la y
+ 2 4 V D CP o w e r
1 2 0 V A C
P o w e r
M o to r
S up p ly
S up p ly
M o to r (sue :2 .O .D a ta .3 )
L a m p (sue :2 .O .D a ta .3 )
N e ut.
C O M
Output CardExample(Transistors)
2 4 V D CO utp ut C a rd
V +
0 0
0 1
0 2
0 3
0 4
0 5
0 6
0 7
2 4 V la m p
R e la y
+ 2 4 V D C
P o w e r
1 2 0 V A C
P o w e r
M o to r
S up p ly
S up p ly
N e ut.
C O M
Output CardExample(Relays)
1 2 0 V A C /D CO utp ut C a rd
in ra c k 0 1I/O gro up 2
0 0
0 1
0 2
0 3
0 4
0 5
0 6
0 7 2 4 V la m p
R e la y
2 4 V D CP o w e r
1 2 0 V A CP o w e r
M o to r S up p ly
S up p ly
Some Design Issues
• DC voltages are usually lower, and therefore safer (e.g., 24V).• DC inputs are very fast, AC inputs require a longer on-time.• DC voltages can be connected to more electrical systems.• AC signals are more immune to noise than DC.• AC power is easier and less expensive to supply to equipment.• AC signals are very common.
Relays
Contactor - Special relays for switching large current loads.Motor Starter - Basically a contactor in series with an overload relay to cut off when too much current is drawn.Arc Suppression - when any relay is opened or closed an arc will jump. This becomes a major problem with large relays. On relays switching AC this problem can be overcome by opening the relay when the voltage goes to zero (while crossing between negative and positive). When switching DC loads this problem can be minimized by blowing pressurized gas across during opening to suppress the arc formation.AC coils - If a normal relay coil is driven by AC power the contacts will vibrate open and close at the frequency of the AC power. This problem is overcome by adding a shading pole to the relay.
Problem: You are planning a project that will be controlled by a PLC. Before ordering parts you decide to plan the basic wiring and select appropriate input and output cards. The devices that we will use for inputs are 2 contact switches, a push button and a thermal switch. The output will be for a 24Vdc solenoid valve, a 110Vac light bulb, and a 220Vac 50HP motor. Sketch the basic wiring below including PLC cards.
Wiring DiagramL 1 N
P L CL 1 N
I:0 /0
I:0 /1
I:0 /2
I:0 /3
a c c o m
O :0 /0
O :0 /1
O :0 /2
O :0 /3
s to p s ta rt
C R 1
C R 1
C R 1
C R 1
M C R
P B 1
L S 1
P B 2
C R 2
C R 2
L 1 ND rill S t a tio n
0 1 0
0 2 0
0 3 0
0 4 0
0 5 0
0 6 0
0 7 0
0 8 0
0 9 0
1 0 0
11 0
1 2 0
1 3 0
R
G
L 1
L 2
S 1
0 3 5
0 5 0
0 6 0
0 7 0
0 9 0
1 0 0
11 0
1 2 0
9 0 -1
1 0 0 -1
1 1 0 -1
1 2 0 -1
9 0 -1
1 0 0 -1
1 1 0 -1
1 2 0 -1
disconnect circuit interrupter
breaker (3 phase AC)normally openlimit switch
normally closedlimit switch
normally openpush-button
normally closedpush-button double pole
push-buttonmushroom headpush-button
(3 phase AC) (3 phase AC)
JIC Wiring Symbols