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Digital Output remains ON during PLC stop mode

Created by: SureshNair at: 11/20/2010 12:22 PM (4 Replies)

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11/20/2010 12:22 PM	Rate (0)
SureshNair Posts: 5 Rating: (0)	Dear experts, I am facing a problem wth the digital output modules. In my project we use 319 CPU along with 322 digital output modules. It was noticed that the digital outputs, which was energised during the run mode will remain ON, if the PLC is switched to OFF mode. There are no LED indications corresponding to the digital outputs, but the output relays are energised. Please advise. Best regards Suresh
SureshNair Posts: 5 Rating: (0)
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11/20/2010 1:09 PM	Rate (0)
Ammy Platinum Member Joined: 4/19/2008 Last visit: 11/21/2024 Posts: 1525 Rating: (159)	SureshNair Dear experts, I am facing a problem wth the digital output modules. In my project we use 319 CPU along with 322 digital output modules. It was noticed that the digital outputs, which was energised during the run mode will remain ON, if the PLC is switched to OFF mode. There are no LED indications corresponding to the digital outputs, but the output relays are energised. Please advise. Best regards Suresh Hi Suresh, Have you checked the Output voltage during above problem? Can you Please provide us a Electrical Diagram For the Same Module? So that we can give you the more Clarification on the same. Also Provide the MLFB no for the all resp. Module.
	Ammy New for every one.............. “No duty is more urgent than that of returning thanks.” If Problem Solved......! I can't help you privately - please post in the Forums
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11/20/2010 3:49 PM	Rate (0)
Ayman Elotaify Platinum Expert Joined: 5/28/2008 Last visit: 1/2/2025 Posts: 4518 Rating: (841)	SureshNair Dear experts, I am facing a problem wth the digital output modules. In my project we use 319 CPU along with 322 digital output modules. It was noticed that the digital outputs, which was energised during the run mode will remain ON, if the PLC is switched to OFF mode. There are no LED indications corresponding to the digital outputs, but the output relays are energised. Please advise. Best regards Suresh Hello, This can happen due to one of the following two reasons: 1. Some modules supports to be energized when the CPU goes to Stop mode. In these types of the modules (in HW configuration), you can select to keep the last valid value or substitute a certain value (0 or 1). Please see the attached picture May be there is some thing wrong in the wiring. Please provide us by the part number of the DO module. 2. May be there are something wrong in the wiring that provide a 24V on the DO channel and make the DO led lit. So please check the wiring. Hope this helps. Attachment DO.JPG (436 Downloads)
	Ayman Elotaify
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11/21/2010 6:29 AM	Rate (0)
SureshNair Posts: 5 Rating: (0)	Hi Ayman, Thanks for the mail. The module number is 6ES7 322 1BL00 0AA0. The output LEDs are not lit as mentioned earlier. Best Regards Suresh
SureshNair Posts: 5 Rating: (0)
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11/21/2010 4:41 PM	Rate (0)
H-H Platinum Member Joined: 7/2/2008 Last visit: 9/30/2024 Posts: 928 Rating: (309)	Hello SureshNair, Please check your wiring as the gentlemen advised. Check your ground (Zero volt). Measure the volt across the relay coil. Try taking out the coil from the relay base and measure the volt across the terminals of the base (wires) while the digital output is off. - If you are still measuring some volts then you have a wiring problem. - If the reading is gone then it's a problemin your coil that's building some energy that's not quickly dissipated. Try using freewheeling diode and see if it gets better. Best regards, H-H

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