Siemens S7-200 User Manual download pdf (Page 19)

Solution Description and Test

As in the contactor circuit, you have

also switched a contact of the output

(Q0.0) parallel to the tripping element

(I0.0).

If, during a cycle, output Q0.0 has been

activated by operation of switch S1 at

I0.0, contact Q0.0 parallel to I0.0 appears

closed in the very next cycle (a few

milliseconds later). This brings about

latching. NC contact I0.1 can terminate

this when switch S2 at I0.1 is operated.

Save your completed program to

hard disk. Then you can load it

complete again at any time and

continue to process it (we will re-

quire the program again for our

OFF Delay example).

Latching

- Introduction

- Normally-Closed (NC) Contact

- Solution Description and Test

- A Different Take on Latching

Output Q0.0

parallel to the

input maintains

itself

Test your program by operating the two switches on the simulator connected at I0.0 and I0.1.

Observe the lamps on the S7-200 or the LAD status!

Begin by switching on I0.0.

I0.1 must be switched off. The LED at I0.0 must light up.

Q0.0 will then light up.

As soon as I0.1 is switched on, Q0.0 becomes ="0".

For test purposes, switch the PLC

to the "RUN" mode.

Then transfer the program to the

PLC to test the function.

Network 1

Latching Revision

Pulse-Oper-

ated Switch

Off-Delay

Timer

Sequencer Appendix

1 2 ... 14 15 16 17 18 19 20 21 22 23 24 ... 73 74

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Siemens S7-200 User Manual Page 19

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