The working voltage of the CPU module is generally 5V, while the input/output signal voltage of the PLC is generally higher, such as DC 24V and AC 220V. The spike voltage and interference noise introduced from the outside may damage the components in the CPU module, or make the PLC not work properly. In the I/O module, optocouplers, photo thyristors, small relays and other devices are used to isolate the internal circuit of the PLC and the external I/O circuit. In addition to transmitting signals, the I/O module also has level conversion and isolation. effect.
Compiler
The programmer is used to generate user programs, and use it to edit, check, modify and monitor the execution of user programs. The handheld programmer cannot directly input and edit the ladder diagram, but can only input and edit the instruction list program, so it is also called the instruction programmer. It is small in size and cheap, and is generally used for programming small PLCs, or for on-site debugging and maintenance.
Using programming software, ladder diagram, instruction list, function block diagram and sequential function diagram programs can be directly generated and edited on the computer screen, and the mutual conversion of different programming languages can be realized. After the program is compiled, it is downloaded to the PLC, and the program in the PLC can also be uploaded to the computer. The program can be saved or printed, and remote programming and transmission can also be realized through the network.
power supply
PLC generally uses 220V AC power supply or 24V DC power supply. The internal switching power supply provides DC 5V, ±12V, 24V and other DC power supplies for each module. Small PLCs can generally provide 24V DC power for input circuits and external electronic sensors (such as proximity switches), and the DC power that drives the PLC load is generally provided by the user.
T8151B
