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Automating Manufacturing Systems - Process Control and ...

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plc timers - 9.20<br />

h<strong>and</strong>_A<br />

I:0/0<br />

A_pushed<br />

B3:0/0<br />

clear<br />

I:0/2<br />

A_pushed<br />

B3:0/0<br />

h<strong>and</strong>_B<br />

I:0/1<br />

B_pushed<br />

B3:0/1<br />

clear<br />

I:0/2<br />

B_pushed<br />

B3:0/1<br />

A_pushed<br />

B3:0/0<br />

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press_on<br />

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Figure 9.20<br />

An example using bit memory<br />

Bit memory was presented briefly here because it is important for design techniques<br />

in the following chapters, but it will be presented in greater depth after that.<br />

9.7 DESIGN CASES<br />

The following design cases are presented to help emphasize the principles presented<br />

in this chapter. I suggest that you try to develop the ladder logic before looking at<br />

the provided solutions.<br />

9.7.1 Basic Counters And Timers<br />

Problem: Develop the ladder logic that will turn on an output light, 15 seconds<br />

after switch A has been turned on.

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