A Programmable Logic Controller (PLC) is a digital operational electronic system designed specifically for use in industrial environments. The T8151B uses a programmable memory in which instructions for performing operations such as logical operations, sequence control, timing, counting and arithmetic operations are stored, and various types of mechanical equipment or production processes are controlled through digital or analog inputs and outputs.
PLCS and relays differ significantly in several ways:
Control mode: T8151B relay control mainly relies on hardware relay to achieve, through the time relay lag action to complete the time sequence control. The PLC control uses the method of program, changes the logic by changing the program, and has higher flexibility and programmability.
Working mode: When the relay control circuit is working, the hardware relays are in a controlled state, and the hardware relays that should not be drawn by various binding conditions are synchronized in the disconnected state. The soft relays in the PLC ladder diagram are in a cyclic scanning working state, and the action order of each soft relay subject to the same condition depends on the program scanning order.
The number of contacts of the components: The number of contacts of the hardware relay is limited, generally only 4 to 8 pairs. The number of soft relay contacts in the PLC ladder diagram can be used without limitation during programming, and can be normally open or normally closed.
Control speed: The relay control relies on the suction and closing action of the mechanical contact to complete the control task, and the working frequency is low and the working speed is slow. The PLC control uses the program command to control the semiconductor circuit to achieve control, stable and reliable, and the running speed is greatly improved.
Counting function: Relay control does not have the function of counting.
Installation and maintenance: After the installation of the system, the flexibility and scalability of the system in the future are poor due to the limited number of electrical equipment contacts and the complexity of the connection.
In general, PLCS and relays are different in terms of control mode, working mode, number of component contacts, control speed, counting function, and installation and maintenance. PLCS offer greater flexibility and programmability, while relay control is more dependent on hardware devices.
