Because the relay in the PLC is not visible outside, change the control does not need to re-wiring, as long as the re-programming just fine!
PLC after the replacement of these intermediate relays into a CPU in a storage bit, the logical relationship between each other by changing the program can be very convenient.
Soft relay
PLC user program (software) instead of the relay control circuit (hardware)
The relay in the PLC equivalent circuit is not the actual physical relay, it is essentially the state of the memory cell. Unit status is "1", which corresponds to the relay connected; unit status is "0", then the relay is off. Therefore, we call these relays "soft relays". So the number of "soft relays" contacts is infinite and can be understood as a programmable controller.
(SOLIDSTATE RELAYS) is not the same thing, state relay abbreviated as "SSR", is a kind of solid electronic components by the composition of the new non-contact switch devices, which use electronic components (such as switching transistor, Silicon and other semiconductor devices) switching characteristics, can be achieved without contact without sparking the purpose of turning on and off the circuit, it is also known as "non-contact switch", it came out in the 1970s, because of its non-touch Point of work characteristics, so that in many areas of electronic control and computer control has been increasingly widely used.
The "contact" of the soft relay in the PLC corresponds to the state of the flip-flop in the chip. The state of the flip-flop is only two, high and low, that is, 1 and 0. When you want to use it, Come out, and then put it into a register, and then operation, so that it can be used indefinitely.
Root ordinary than with the following characteristics
1, the reaction speed, low noise, low energy consumption. small volume.
2, powerful, easy programming, you can always modify the program,
3, high precision control, can be complex program control.
4, can control the process of automatic detection.
5, the system is stable, safe and reliable.
