PLC is a kind of industrial control computer system, its control object is industrial production process, its connection with industrial production process is realized through I0 module, modbus I0 module is the bridge between programmable controller and production site.
(1) The external wiring method of the switching IO module has only two states of ON and OFF for the input signals. The on/off status of each input/output point is indicated by an illuminated diode. The on/off status of each input/output point is indicated by a light-emitting diode, and the external wiring is generally connected to the terminal block on the module panel. Some modules use a detachable socket terminal block, which allows for quick module replacement without disconnecting the external wiring on the terminal block. Sink modules have a single common point for all input/output circuits, and all input/output points share a common power supply. The input/output points of grouped modules are divided into several groups, and each group has a common point for each input/output circuit, and they share a common power supply. The groups are separated and can use different power supplies. Each input/output of a partitioned module is isolated from each other, and each input/output point can use a separate power supply, if their COM terminals are connected, these points can use the same power supply.
(2) Input interface circuit
PLC has the advantage of high interference immunity. In its input terminal, all input signals are after Photoelectric coupling and RC circuit filtering before sending to the internal amplifier of the PLC. Picking strong photoelectric coupling and RC filtering measures can effectively eliminate interference caused by stray electromagnetic waves in the environment, and the input/output of the optocoupler has a high insulation resistance, can withstand more than 1500V high voltage and not be broken, so this anti-interference means has been used for other circuits.
(3) output interface circuit
Programmable controller output mode according to the load using power to be divided, there are DC output, AC output and AC/DC output in three ways. According to the type of output switching devices to be divided, there are transistors, thyristors and relays three kinds of output mode.O
(4) Special function module.
With the wide application and development of programmable controllers in I industry control, in order to enhance the functions of programmable controllers and expand their applications, manufacturers have developed many special function modules for users to choose. In order to enhance the functions of programmable controllers and expand their application scope, manufacturers have developed many special function modules for users to choose.