rslogix 500 no output

fishkeeper

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Join Date
Dec 2011
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tn
Posts
9
I got a 1400 series c on test bench with 1 rung and 1 input and 1 output and cant get output to come on in software .It downloads and works fine on plc .It shows output on plc display and rslogix software but if i toggle bit in software i get no green output so no trouble shooting a program with software .What could be wrong?
 
The PLC is looking at its inputs hundreds or maybe thousands of times per second. If it sees an input that does not have voltage, it writes a zero to that address. Hundreds or thousands of time each second. If you toggle that bit on, it is toggled only until the next time the PLC reads its inputs. At that time, it will return the bit to the correct state. Until you can toggle faster than the PLC scans, toggling the input is not usually effective.

The same is essentially true for your output. Only this time the logic is determining whether your output bit should be on or off. Again, you might toggle it, but on the next scan, the logic will reset it to the correct state. And that scan also happens hundreds or thousands of times per second.

So toggling bits may work, or it may not do anything at all. It can be very hit and miss because of the speed at which the program gets scanned.

Forcing on the other hand, overrides the physical input. Or on the output side, it overrides the logic to "force" a physical output to energize or deenergize. Note though that forcing an output only affects the physical output. The state you see in the software will always show you the logical state for that output. So while a physical output may be energized, in the logic it may still appear to be deenergized.

OG
 
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when I toggle bit in software it stays toggled till I toggle it off .I can force on but forces enable is greyed out and cant be used
 
In the upper left of the programming window does it have a green box that say Remote Run?


Or possibly a different color that says Remote Program or Program?


If not running click on the drop down in that box & click on RUN, then confirm.



If the physical switch is in program it won't let you and should popup a warning.
 
In the upper left of the programming window does it have a green box that say Remote Run?


Or possibly a different color that says Remote Program or Program?


If not running click on the drop down in that box & click on RUN, then confirm.



If the physical switch is in program it won't let you and should popup a warning.

yes, its green remote run
 
Go to your controller properties under the compiler tab and insure the "Enable Force Protection" is NOT checked.
You will need to do this offline and re-download if changes needed.
 
Let's not forget some other basic things that might be wrong.

Is the rung in the MAIN ladder file or a subroutine?

If the output LCD is lit up but the voltage doesn't appear to change at the output point or the load doesn't respond, then we need to ask is the PLC wired right?

Note that those models with FET outputs require a DC Common to be wired where other models with relay outputs don't require it.

When you say you are toggling a bit and it stays toggled, what's the address of that bit?

As for this:
Go to your controller properties under the compiler tab and insure the "Enable Force Protection" is NOT checked.
You will need to do this offline and re-download if changes needed.
The default is not checked and that setting doesn't apply to Micrologix.

The default for a new program is to have forces disabled, which you can enable offline and download by clicking on the arrow next to where is says "Forces Disabled".
 
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Is the rung in the MAIN ladder file or a subroutine?
main rung
Go to your controller properties under the compiler tab and insure the "Enable Force Protection" is NOT checked.
You will need to do this offline and re-download if changes needed.
only "allow future access" is checkable evrything else greyed out

plc.jpg
 
Toggling I:0/1 while online to a PLC in run mode will do nothing at all useful. You can right-click and force it on, but only if forces are enabled. To enable them, you have to go into the status file S2 and toggle S:1/5 on while offline. Then download to the PLC. You can't change it online. Note: while offline, the "Forces Enabled" dropdown in the top left corner appears to parallel the state of S:1/5. Next time I'm online, I'll tinker with it a little more.
 
Curious?

The picture shows a driver of 1784_U2DHP-1 driver. That is a USB to DH+ converter.
The ML1400 does not support DH+ protocol (or hardware connection)
How are you connected to the ML1400?
 
Toggling I:0/1 while online to a PLC in run mode will do nothing at all useful. You can right-click and force it on, but only if forces are enabled. To enable them, you have to go into the status file S2 and toggle S:1/5 on while offline. Then download to the PLC. You can't change it online. Note: while offline, the "Forces Enabled" dropdown in the top left corner appears to parallel the state of S:1/5. Next time I'm online, I'll tinker with it a little more.
there should be a way of troubleshooting the program in rslogix even though i know this simple program will work i should be able to toggle the input and see the output light up green should i not?

The picture shows a driver of 1784_U2DHP-1 driver. That is a USB to DH+ converter.
The ML1400 does not support DH+ protocol (or hardware connection)
How are you connected to the ML1400?
My laptop only has usb so i have usb to 9pin converter connected to a 1761-CBL-PM02 cable .
 
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In general, you use the "DF1 Devices" driver set up for DF1 Full Duplex and the COM port that is represented by your USB/Serial converter.

Because the 1784-U2DHP appears to Windows like a serial port and uses DF1 full duplex protocol over USB, that driver works by coincidence with your MicroLogix.

The MicroLogix 1400, of course, also has Ethernet built-in. But let's solve one problem at a time.


I recommend an excellent live + screen demo of how forcing works on the MicroLogix 1100 (a very similar controller) by Friend of the Forum Tim Wilborne, on YouTube:

https://www.youtube.com/watch?v=Hop3X-Smi6E

I believe the MicroLogix 1400 doesn't use the same "forces are always enabled" method as the MicroLogix 1000, 1100, 1200, and 1500, which is why the Forces Enabled is always highlighted yellow on those controllers.

Open your Status data file, and maybe switch to Binary instead of Structured, to see if I/O forcing is disabled by bit S:1/5.

The fact that the force "ON" notation is in black instead of red ">ON", and the Forces Disabled status showing, suggests that S:1/5 = 0.
 
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I believe the MicroLogix 1400 doesn't use the same "forces are always enabled" method as the MicroLogix 1000, 1100, 1200, and 1500, which is why the Forces Enabled is always highlighted yellow on those controllers.

Open your Status data file, and maybe switch to Binary instead of Structured, to see if I/O forcing is disabled by bit S:1/5.

The fact that the force "ON" notation is in black instead of red ">ON", and the Forces Disabled status showing, suggests that S:1/5 = 0.


I have a 1400 as part of my home automation system [Bulletin 1766 Ser B] and it shows Forces Enabled all the time. I have no forces present and just tried and can not disable them same as all the other ML's. Plus I can't change S:1/5 to 0 online.



Is there maybe a newer Series C or D that does this that my RSLogix500 ver9.0 doesn't support?
 

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