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Automating Manufacturing Systems - Process Control and ...

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plc timers - 9.22<br />

Solution:<br />

A<br />

On<br />

L<br />

On<br />

t_0.DN<br />

TON t_0<br />

Time base: 1.0<br />

Preset 20<br />

Light<br />

L<br />

t_0.DN<br />

t_1.DN<br />

TON t_1<br />

Time base: 1.0<br />

Preset 10<br />

On<br />

U<br />

On<br />

count.DN<br />

CTU<br />

Preset 3<br />

Accum. 0<br />

Light<br />

count<br />

U<br />

Figure 9.22<br />

A More Complex Timer Counter Example<br />

9.7.3 Deadman Switch<br />

Problem: A motor will be controlled by two switches. The Go switch will start the<br />

motor <strong>and</strong> the Stop switch will stop it. If the Stop switch was used to stop the motor, the<br />

Go switch must be thrown twice to start the motor. When the motor is active a light should<br />

be turned on. The Stop switch will be wired as normally closed.<br />

www.PA<strong>Control</strong>.com

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