adccommunitymod (AutomationDirect) asked a question.
Created Date: June 25,2014
Created By: smcmains
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I'm using a DL05 PLC to control a small conveyor, I was using Y4 output to turn on a motor for the conveyor through a Fuji contactor SC-E02G (24vdc coil). I ran 24V to one side of the coil and Y4 (0V) on the other side of the coil to activate it. Now the contactor stays in (on) all the time, its getting 0V from Y4 output all the time even though the output is not physically on. The LED is not on and when monitoring it through DirectSoft5 its not showing on either. I have 0V going to Common on the output side (the outputs are NPN). I thought maybe it was a bad output so I moved it over to Y5. It cycled one time and now I'm having the same issue with Y5. Has anyone had this issue before? Its a very basic setup and not something that should be causing me any issues, I dont even have the motor wired up to the contactor yet as I was just testing the PLC program without any load on anything.
Created Date: June 25,2014
Created by: Do-more PE
You are probably burning the output closed with the CEMF surge when the output is de-energizing. See this application note for more information on protecting your outputs from transient surges from coils.
Created Date: June 25,2014
Created by: smcmains
So I'm assuming that the SZ-Z1 surge suppressor will also work for this application with the Fuji contactor?
Thanks for the information....
Created Date: June 25,2014
Created by: jwbaker3
That is the suppressor you need. We normally use a single pole relay $8.75 (relay and base) from ADC to isolate the load from the PLC. It is cheaper and quicker to replace a $4.75 relay than a PLC, and the relay's contacts are rated at 15 amps. We use a small MOV across the relay coil (load on PLC) and don't use the suppressor on the contactor coil.
JW
Created Date: June 25,2014
Created by: Do-more PE
If you have any coil on the same power supply that serves the PLC in any capacity, you need surge protection across the coil. Surges don't just affect what is directly tied to the coil, they affect everything on that circuit.
Created Date: June 25,2014
Created by: jwbaker3
We always use a separate power supply for the PLC and the analog I/O to help keep the noise controlled. We never run the contactors, starters or discrete I/O on the same supply as the PLC. 99% of our projects are on machines with 3 phase motors and drives so we always use a power line filter for the PLC and the analog power sources.
JW
Created Date: June 25,2014
Created by: Do-more PE
Just wanted to clarify that was the case for future readers. :)
Created Date: June 25,2014
Created by: smcmains
I'm using a DL05 PLC to control a small conveyor, I was using Y4 output to turn on a motor for the conveyor through a Fuji contactor SC-E02G (24vdc coil). I ran 24V to one side of the coil and Y4 (0V) on the other side of the coil to activate it. Now the contactor stays in (on) all the time, its getting 0V from Y4 output all the time even though the output is not physically on. The LED is not on and when monitoring it through DirectSoft5 its not showing on either. I have 0V going to Common on the output side (the outputs are NPN). I thought maybe it was a bad output so I moved it over to Y5. It cycled one time and now I'm having the same issue with Y5. Has anyone had this issue before? Its a very basic setup and not something that should be causing me any issues, I dont even have the motor wired up to the contactor yet as I was just testing the PLC program without any load on anything.