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Automating Manufacturing Systems - Process Control and ...

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plc timers - 9.27<br />

Solution:<br />

TS1 LS1 LS3 C5:0/DN<br />

SOL1<br />

L<br />

LS2<br />

SOL1<br />

U<br />

T4:0/DN<br />

SOL1<br />

CTU<br />

Preset 5000<br />

Accum. 0<br />

C5:0<br />

SOL1<br />

RTO T4:0<br />

Time base: 1.0<br />

Preset 5<br />

T4:0/DN<br />

C5:0/DN<br />

LIGHT<br />

L<br />

RESET<br />

T4:0 RES<br />

- what do we need to do when the machine is reset?<br />

Figure 9.27<br />

A Shear Press <strong>Control</strong>ler Example<br />

9.8 SUMMARY<br />

• Latch <strong>and</strong> unlatch instructions will hold outputs on, even when the power is<br />

turned off.<br />

• Timers can delay turning on or off. Retentive timers will keep values, even when<br />

inactive. Resets are needed for retentive timers.<br />

• Counters can count up or down.<br />

• When timers <strong>and</strong> counters reach a preset limit the DN bit is set.

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