The key to analyze the input terminal of PLC, common type wiring - output terminal

At present, PLC in industrial production and automation control utilization rate is very high concentration of control equipment, PLC to replace the heavy ark of relay, ac contactor cabinet and so on, gradually widespread use in the production and control, PLC, the correct connection is the premise condition of PLC function, skilled master PLC input port and output port connection is necessary for every power operation personnel. Under normal circumstances, the PLC AC220V power input, in order to provide PLC operation power supply. PLC output power port for DC24V commonly, is the power output of PLC. PLC in use process, the input and output it is very important to the correct wiring, wiring is the precondition of PLC to work correctly. Below we focus to analyze the input terminal of PLC, the output end of the common connection type:

a common connection, input port types and object: PLC input port is: 1, the switch quantity signals: button, trip switch, switch, proximity switch, dial the code switch and so on. A simple example is more easy to clear:

PLC and push button switch wiring diagram

button or proximity switch wiring is shown in: PLC switch wiring, and a head of access to the input end of the PLC ( X0, X1, X2, etc. ) Together, on the other side and public access to the PLC port ( COM) 。

2, analog signals: general for various types of sensors, such as: pressure transmitter, liquid level transmitter, remote transmission pressure gauge, thermocouple and thermal resistance, and so on. Analog signal acquisition equipment, wire ( Two wire or three wire system) Different wiring methods will be slightly different. As shown in figure:

FIG. 8 5 interface circuit of PLC and sensor component (

一) Two line type sensor; ( b）

two, three line sensor output port connection. The PLC output port connection generally can be divided into the following three conditions: 1, the relay output. 2, transistor output. 3, thyristor output.

PLC output in a different way, the power of the output load that type is also different. As shown in figure: this is input and the output of PLC controller basic wiring, belong to the basic knowledge of PLC.

three, three common sense in the process of PLC wiring: 1, the PLC power supply circuit. PLC control system of power supply in addition to the ac power, dc power supply also includes PLC, in general, PLC, ac power can directly by the mains supply, and input devices ( Switches, sensors, etc. ) Dc power supply, and output devices ( Relay) The dc power supply, etc. , had better take independent dc power supply. Most of the PLC with 24 v dc power supply, current is needed only when the input or output devices are not a lot of cases, to use the PLC with dc power supply.

2, and the PLC input port and output current rating. Input port of PLC with general for DC24v power supply, input port of each point in 5 ma - current quota Between 7 ma, the electric current is generated when the input port short after the maximum current, when the input port has the certain load, the flow of current will be reduced correspondingly. PLC input signal passing the required minimum current is commonly 2 ma, in order to ensure the effective minimum input current signal, pick up equipment total impedance input port is normally less than 2 k.

FIG. 8 5 interface circuit of PLC and sensor component (

一) Two line type sensor; ( b） Three wire sensor

that is to say, when the input port of the sensor power is bigger, need to pick up a separate external power supply.

3, PLC output port can generally by the maximum current varies with PLC models, most between 1 a and 2 a, when the load current is greater than the PLC port when the maximum rated current, generally need to increase the intermediate relay connect the external contactor or other equipment.

PLC controller correct wiring is the precondition of effective operation of PLC, PLC basic skills, skilled master PLC wiring common sense is very necessary.

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