Page 717 - Mechatronics with Experiments

PROGRAMMABLE LOGIC CONTROLLERS 703
L1 L2 L1 L2

AC input AC output
module
module SOL
1
1
2
2
3 CR
3
4
4 MTR
Common
Common

(a) (b)

DC(+) DC(–)
or GND DC(+) DC(–) or
GND
DC input DC output
module
module SOL
1
1
2
CR
3 2
CR
4 3
4 HTR
Common
Common

(c) - Current sinking (d) - Current sourcing
FIGURE 9.5: Wiring of PLC I/O modules to the field devices: (a) AC input module, (b) AC
output module, (c) DC input module (shown wired as current sinking), (d) DC output module
(shown wired as current sourcing).

Movable
Armature
contacts
Power
circuit

Stationary
Return contacts
spring

Control
Electromagnet and Circuit
operating coil
FIGURE 9.6: Operating principles of relay, contactors, starters.