PLC ladder programming principles and programming methods

(1) Input / output relay, internal auxiliary relays, timers, counters and other devices of the contact can be used repeatedly, without complex program structure to reduce the use of contacts. (2) Each line ladder left the bus started, the coil terminates at the right bus. Contacts are not on the right side of the coil, as shown below

(3) In addition to stepping procedure, any coils, timers, counters, and other advanced instruction can not be directly connected to the left bus bar.
(4) In the process, does not allow the same number twice coil output (dual coil output). The following ladder is not allowed.

(5) does not allow the bridge circuit.

(6)Shall be prepared by the sequential program from top to bottom, from left to right to prepare the way. To reduce the number of steps in the implementation of the program, the program should be to the left and right big small big small.

(7) as an input device with a normally open contact

(8) PLC programming experience commonly Design
In the traditional relay – contactor control diagram and typical PLC based control circuit, based on the experience accumulated translation, revised and improved to give final control procedures.

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