應遵守梯形圖語言中的語法規定設置中間單元在梯形圖中，若多個線圈都受某一觸點串并聯電路的控制，為簡化電路，在梯形圖中可設置用該電路控制的輔助繼電器，類似于繼電器電路中的中間繼電器。分離交織在一起的電路 設計梯形圖時以線圈為單位，分別考慮繼電器電路圖中每個線圈受到那些觸點和電路的控制，然后畫出相應的等效梯形圖電常閉觸點提供的輸入信號的處理設計輸入電路時，應盡量采用常開觸點，如果只能用常閉觸點，梯形圖中對應觸點的常開/常閉類型應與繼電器電路相反。時間繼電器的瞬動觸點的處理對于有瞬動觸點的時間繼電器，可以在梯形圖中對應的定時器的線圈兩端并聯輔助繼電器，后者的觸點相當于時間繼電器的瞬動觸點。斷電延時的時間繼電器的處理用通電后延時的定時器來實現斷電延時功能。外部聯鎖電路的設計在梯形圖中設置對應的輸出繼電器的線圈串聯的常閉觸點組成的軟件互鎖外，還應在PLC外部設置硬件互鎖電路。熱繼電器過載信號的處理
The intermediate unit shall be set according to the syntax provisions in the ladder diagram language. In the ladder diagram, if multiple coils are controlled by a series parallel circuit of a contact, in order to simplify the circuit, the auxiliary relay controlled by this circuit can be set in the ladder diagram, which is similar to the intermediate relay in the relay circuit. When designing the ladder diagram of separated and intertwined circuits, take the coil as the unit, respectively consider which contacts and circuits control each coil in the relay circuit diagram, and then draw the corresponding equivalent ladder diagram. When designing the input circuit, the normally open contact should be used as far as possible. If only the normally closed contact can be used, the normally open / normally closed type of the corresponding contact in the ladder diagram should be opposite to the relay circuit. Processing of instantaneous contact of time relay for time relay with instantaneous contact, the auxiliary relay can be paralleled at both ends of the coil of the corresponding timer in the ladder diagram, and the contact of the latter is equivalent to the instantaneous contact of time relay. The processing of the time relay of power-off delay uses the timer of power-on delay to realize the function of power-off delay. For the design of external interlocking circuit, in addition to the software interlocking composed of normally closed contacts connected in series with the coil of the corresponding output relay in the ladder diagram, the hardware interlocking circuit should also be set outside the PLC. Processing of overload signal of thermal relay
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