GE logic

Hi, I am new to GE, just got an additional plant to cover with three GE PLC's on a network, running Proficy Machine Edition. THe first two plc's turn on a flashing red light on the building on a new alarm. I need to make the third plc also flash the light on a new alarm in it.

There already is logic for a new alarm to sound a horn in the control room. I parallelled a new coil in the same rung as the horn logic. Edit: the rung text doesn't come through as typed. QSP4 is branched under the horn
.QSP1
--------[newalm]---------------------(horn)
..........................l
..........................l......... QSP4
..........................l----------(light)

The horn was added previously and the output for it is QSP1(spare relay 1). I am using QSP4 (spare relay 4), also provided with the original install.

My issue is that when I put in the 'coil' for QSP4, the output has an M inside it. The horn output has bold lettering QSP1, and no M inside the coil. The properties for both coils look the same. The logic knew that QSP4 was for 'spare relay 4. The rung does work, when I have a new alarm, relay 4 is energized, I wired the N.O. contacts, and the flashing light on the building flashes until the alarm is acknowledged. Just wondering about that M inside the coil. Thanks in advance.

The "M" inside the coil instruction means that the variable associated with it has been configured to be retentive. GE lets you define individual variables to be retentive or non-retentive rather than a range of addresses or specific instruction types like other PLC brands.

Snip...
Edit: the rung text doesn't come through as typed.

Click to expand...

Here is how to keep the ladder diagram looking correctly. Click on "Go Advanced" button at the bottom, type in your ladder, "Highlight it", then click on the little button that looks like a relay contact symbol. Just don't preview the post before posting it.

Is this what you were trying to draw?

                                      QSP1

--------[newalm]------------------+--(horn)

                                  |

                                  |   QSP4

                                  +--(light)

Since I didn't configure it to be retentive, it must default to retentive when I added the output. The other 'spare relay' logic for QSP1, QSP2, QSP3 are not retentive, so I'm not sure I want the QSP4 to be retentive. Can you explain what retentive/nonretentive means as far as the logic?

thanks for the quick answer.

-------[FOUT ]----------------------(QSP1 )
|
| QSP4
------( M )

Yeah, ther we go, JRW, thanks, oops, still didn't get it right

Are these all %Q addresses? If so, someone configured that one to be retentive because default is non-retentive.

If you use SET/RESET instructions with a retentive address, it will "remember" its state across a power down/power up event and revert to its state prior to the power cycle. A non-retentive address will power up in the OFF state.

I'm talking about -(SM)- and -(RM)- instructions where the coil is in the ON state but the logic controlling both the -(SM)- and -(RM)- is false bothe before and after the power cycle.

The same rules apply to a coil instruction that uses a contact from the same address to seal itself on.

Yes they are %Q addresses. Since it is a spare relay for any number of possible uses, I am not sure why the programmer would have done this. Since the light (QSP4), serves the same function as the horn (QSP1)- turn on with each new alarm, turn off when the alarm is acknowledged, I think the outputs should have the same config. Can I change QSP4 to be non-retentive?

edit; In fact, the other two plc's in the system already turn on the light, and their QSPX relays are non-retentive.

mapman88 said:

-------[FOUT ]----------------------(QSP1 )
|
| QSP4
------( M )

Yeah, ther we go, JRW, thanks, oops, still didn't get it right

Click to expand...

 

-------[FOUT ]------------------+---(QSP1 )

                                |

                                |    QSP4

                                +----( M )

Everytime you edit it, the spaces are stripped out. You'll have to re-add them.

Can I change QSP4 to be non-retentive?

Click to expand...

Yes, right click on the variable in the navigator window and open the properties. You will find a true/false selection for retentive.