scan operation

[FONT=&quot]Note /my plc [/FONT][FONT=&quot] LG GLOFA AND[/FONT][FONT=&quot] gm7 mo
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The memory bits that store the active step must be retentive.
You should also detect in the program if the program is started up while the sequence is not finished, i.e. when power returns after a power failure. In that case you should wait for the operator to continue the sequence by a pushbutton or switch.

Apart from that I have no experience with LG PLCs.

Please can u give me some appliacation in lader diagram and i glad to reply

Why not just get a UPS on the supply?

Oceansoul said:

Why not just get a UPS on the supply?

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It's worth noting that when I did a project in Iran, there was a big problem with brownouts (i.e. extended periods of reduced voltage, not power loss). A UPS should be selected with care under such circumstances, as you can easily drain it under such circumstances.

On the original question - if you use retentive bits you should be fine. I am not familiar with your PLC type, but often you need to declare and allocate memory for retentive memory rather than use RAM.

Generator ?

rigicon said:

Generator ?

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Certainly can't hurt - power outages are the bane of manufacturers over there, and fuel is (still) cheap.

PLC program and power

Here (south Florida, USA) we have at times marginal power provided by the local utility, and a very lightning active area in the summertime.
Each of our PLCs have a dedicated UPS. Each UPS has a "relay output card" installed in it - with the relay contacts going to Digital Input modules on the PLC. We have written parts of the PLC program so that the running status of designated equipment is stored by the PLC at all times. When the PLC senses a power outage (from the UPS relay card) it suspends operation of this plant equipment. Then when the utility power is restored (for a certain length of time) the equipment is restored to it's previous state. Works quite well, and lets the plant operators concentrate on other alarms associated with the power outage.