plc What is the role of the power module

plc generally have small internal switching power supply, the output voltage is used for their own chips, components and external sensor power supply module , a large current can also give small executive power components, such as solenoid valve relays, etc.
plc cpu host power supply is limited, if you add the expansion unit, or peripheral unit. When using host power beyond its rated value, then you need the power module.

Input Output Module works

plc digital output (hereinafter referred to as modules), for switching bus system fire radio systems and fire radio broadcasts normally between. Output module is embedded microprocessor, microprocessor and fire alarm controller communications, power bus brownout detect, input and output line fault detection, output control, digital input module signal logic state judge, the status indicator control. Module after receiving the fire alarm control start command, pull the relay, the scene shifted from the normal speakers to fire radio broadcasts, and light indicator, while the answer signal information to the fire alarm controller, indicating that the switch was successful

Modules include what kinds of

 plc module should include IO modules (analog and digital input and output modules), cpu module, communications module, the general PLC does not require power modules, such as S7-200, while others require a power supply module PLC, such as S7-300 . According to the actual needs of the PLC module combination, such as CPU + DIC) + AI (analog input) + DO (digital output) + AO (analog output) + CP (communication module), if necessary, together with the PS (power supply module) basically able to achieve the desired purpose.