Weird situation on plant. One bus out of three of 9 contactor on SLC 5/05 not working as it suppose to. It is connected to Relay output module of SLC 500. 24 V dc is available at the coil (no volt coil) terminals of all the contactor. If just flicker the on off switch then start working. While the plant is running, suddenly stop whole bus of 7 contactor. But 2nd and 3rd bus stays at normal working. Electrically tests every thing is ok.
Slc 500
- Thread starter jaykarwal
- Start date
Is the program turning off the group of relay outputs, or are they failing?
If they are being turned off there may be something in the program writing a 0 to the output card, which will turn them all off.
If they show as on, but are not energizing the outputs, then I would suspect a (intermittent) fault in the relay output card - maybe it shuts down if overheats or similar.
If they are being turned off there may be something in the program writing a 0 to the output card, which will turn them all off.
If they show as on, but are not energizing the outputs, then I would suspect a (intermittent) fault in the relay output card - maybe it shuts down if overheats or similar.
Thanks Aabeck.
In programming, required outputs are high mean being turned off on. I was suspecting output card issue.
OkiePC
Lifetime Supporting Member
Relays are good for about a half million cycles under normal loads and then they will stick, or hesitate.
You should be able to test the relay in question to ensure it is working right. I once worked on some machinery that would get to the life expectancy of one particular slot relay output card about every 6 months due to the high cycle rate of those outputs. I was able to convert it to a solid state output.
I am not saying with certainty that you need to modify anything or that your output relay is failing, but they do have a limited life span even under perfect conditions.
You should be able to test the relay in question to ensure it is working right. I once worked on some machinery that would get to the life expectancy of one particular slot relay output card about every 6 months due to the high cycle rate of those outputs. I was able to convert it to a solid state output.
I am not saying with certainty that you need to modify anything or that your output relay is failing, but they do have a limited life span even under perfect conditions.
Another thing to consider about relay outputs -
If you are using a PLC for home automation or Christmas lights, relays make noise in a quiet environment like a home or office. The first time I tested a relay based system I was surprised at the noise and quickly replaced them with TRIAC and transistor outputs.
If you are using a PLC for home automation or Christmas lights, relays make noise in a quiet environment like a home or office. The first time I tested a relay based system I was surprised at the noise and quickly replaced them with TRIAC and transistor outputs.
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