PLC knowledge answer

1. What are the types of PLC switching output interfaces? What are the characteristics of each?

Thyristor output type: under normal circumstances, it can only carry AC loads, with fast response and high operating frequency;
Transistor output type: under normal circumstances, it can only carry DC loads, with fast response speed and high operating frequency;
Relay output type: under normal circumstances, it can carry AC and DC loads, but its response time is long and its operating frequency is low.

2. According to the structure type, what are the types of PLC? What are the characteristics of each?

(1) Integral type: the CPU, power supply, and I/O components are all concentrated in one chassis, with compact structure and low price. Generally, small PLCs adopt this structure;
(2) Modular type: each part of the PLC is divided into several separate modules, and different modules can be selected according to the needs to form a system. It has the characteristics of flexible configuration, convenient expansion and maintenance. Generally, medium and large PLCs adopt this structure. Modular PLC is composed of a frame or base plate and various modules, and the modules are mounted on the sockets of the frame or base plate.
(3) Stacked type: Combining the characteristics of the integral type and the modular type, the CPU, power supply, I/O interface, etc. of the stacked PLC are also independent modules, but they are connected by cables, so that the system is not only configured Flexible and compact.

3. What is the scan cycle of PLC? What is it mainly affected by?

The scanning process of PLC includes five stages: internal processing, communication service, input processing, program execution, and output processing. The time required for one scan of these five stages is called the scan cycle.
The scan cycle is related to CPU running speed, PLC hardware configuration and user program length.