Design steps of PLC timing diagram

A timing diagram is a graph showing the change of a signal over time. The horizontal axis is the time axis, and the vertical axis is the signal value, which is 0 or 1. The method of designing PLC programs based on this graph is called the timing diagram method. The timing diagram is derived from the work of using an oscilloscope to analyze electrical hardware. It can be used to analyze and determine the timing relationship between related logical quantities. The general steps of designing a PLC program using the timing diagram method are as follows:

1) Draw a timing diagram. Draw the timing diagram of the input and output signals according to the requirements and establish an accurate time correspondence.

2) Determine the time interval. Find the critical points of time change, that is, the time points when the output signal should change, and divide the time period into several time intervals based on these points.

3) Design timing logic. You can use multiple timers to establish different time intervals.

4) Determine the action relationship. According to the corresponding relationship between each action and time interval, establish the corresponding action logic and list the logical expressions of each output variable.

5) Draw a ladder diagram. Draw a ladder diagram based on the expressions of timing logic and output logic.

The premise of using the timing diagram method is that there is a corresponding time sequence relationship between the input and output, and their respective changes are carried out in time sequence. Therefore, if this premise is not met, it is impossible to draw a timing diagram, let alone use this method.

The above briefly introduces 6 common programming methods. In addition, there are matrix design method, subroutine design method and high-level language design method.