E10 PLC on Pause

[EDGAR]

Hello
I?m having an issue with an E10 PLC, but first I have a few questions.
1- What can possibly cause an E10 PLC to go in to ?Pause Mode? on its own? The PLC was unresponsive and when I connect my laptop to it the TRI software gave me a message that the PLC was in user ?Pause Mode?.
2- After resetting the PLC through the software from ?Pause Mode? only some of the logic is executed, from the second rung down. What can this be? Is like the PLC doesn?t detect the input to be on.
3- Power supply is 24 VDC with a SOLA power supply.

I have this PLC installed controlling a sump ejector pumps with a few relays interfacing voltages. The floats power a relay which activates input in the PLC. And the outputs power a relays that starts the pump. The PLC operation is very simple and straightforward. Input1 is activated output 1 is energized, Input 2 is activated output 2 is energized together with a timer. If the timer times-out and the 2 input still activated then energized the alarm and the last output will be energized to help with the load. For some strange reason this work for about a week, after a week the plc goes in to an unresponsive mode ?Pause? and it doesn?t do anything. This is the second plc and it is doing the same thing.

Please advice,
Ed

[support]

E10 does not support any kind of PAUSE function in its program and we have not heard of any report of E10 being PAUSEd on its own.  

Was the E10 powered down and then powered up when this happened? Or was the power continuously applied to the PLC when it stopped working?  I ask this because when the E10 is powered up the CPU perform a checksum to determine if the code is still good. If it discovers any bit changes it will paused the program to prevent execution of a bad program. The online monitoring screen should report that the code is corrupted and the program paused.

If the power was still applied to the E10 when it paused, then did you try to perform a power-on reset of the PLC and would it work? If power on reset and the PLC works that means that the EEPROM was intact but RAM was corrupted. But if after power on reset the PLC is still paused that means that the EEPROM is corrupted.

In both cases it appears that the CPU operation is affected by electrical noise in the system. What kind of output load are the E10 driving? If it is large inductive load such as solenoid or large contactor, did you wire a fly back diode or TVS to suppress electrical noise?

[EDGAR]

The PLC as far as I know did not lose power, it just stop working. After connecting my laptop to the PLC I was surprise the PLC still can communicate and immediately after I get the pause message, using the WinTriLOGIC software I press the Pause Button on the software and after that the plc was responsive but only executed some of the logic not all.
I did not receive any message of memory corruption or else just that the PLC is in User Pause. Once I cut the power and restore the PLC went back to operation normally executing all the logic.
The E10 only drives a two 24 VDC relays, these relays activates the 120 VAC pump contactors. The sump floats activates the input relays based on the level. These are submersible floats, to cancel the turbulence I wire the signal through a time delay relays then to the input relay which activated the PLC input on a separate circuit.

The power supply power the PLC and the relay output. The 24 VDC supply from the PLC connect to each of the relays that activates by floats. When the relays close the input is activated and the PLC starts the pump.

New changes:
I really thought it was a voltage problem or surge caused by the float mechanism using 24VDC from the PLC for simplicity. Now only the PLC output and inputs uses the 24VDC from the Power supply, I wire the float 120VDC to activate the relays independently from the PLC. Now the PLC only uses the 24VDC, the PLC interact with the rest of the device with relays. Floats and contactors, etc. uses the 120VDC directly from the Pump starter box.

Thank you,
Ed

[EDGAR]

It happened again. I think these floats are causing surge in the power supply line going to the DC power supply. Can anyone suggest a surge suppressor or a maybe a capacitor to be installed on the PLC power input? I?m really out of options here. The PLC is getting 24VDC from the Power supply and the power supply gets the 110VAC from the main transformer and is the same powering the submersible floats.

Anything will be greatly appreciated!

Ed

[support]

You may want to try to suppress the inductive noise generated when the power to the 120V float is cut. These are high energy surge pulses that no only can cause havoc to electronics but also can severly shorten the life of the contactor's relay contacts.

You can use a MOV (metal oxide varistors) of suitable values. Google for some selection guides. One of them I found can be downloaded from this website:

www.littelfuse.com/data/en/Application_Notes/ec608.pdf

As for the 24VDC feed to the PLC, you may or may not need a filtering depending on whether the noise is coupled to it electromagnetically (i.e. over the air) or through the power supply.