ronaldshelton28
Member
Hello I can use a output to turn on an input. The question is should and why or why not?
Output to turn on a Input
- Thread starter ronaldshelton28
- Start date
Ken Roach
Lifetime Supporting Member + Moderator
Is this a rhetorical question, a homework question, or a question about integrating separate PLC control systems ?
Some PLC outputs have enough "leakage" in their circuitry that they will turn on the input point of a directly-connected PLC input circuit. This is especially true with 120V AC triac circuits.
The more information you can provide about your application or question, the better the quality of advice you will receive on this Forum.
Some PLC outputs have enough "leakage" in their circuitry that they will turn on the input point of a directly-connected PLC input circuit. This is especially true with 120V AC triac circuits.
The more information you can provide about your application or question, the better the quality of advice you will receive on this Forum.
Mickey
Lifetime Supporting Member
I have seen this done as a watchdog to insure remote I/O is working.
Just one possible reason.
Just one possible reason.
alive15
Member
You mean to turn on like a prox switch or something? I don't get the strategy behind this method.
This seems like a good idea, but if you are using remote ethernet i/o, will you not have a tag for communication itself that can be used to check this?
This seems like a good idea, but if you are using remote ethernet i/o, will you not have a tag for communication itself that can be used to check this?
alive15
Member
I guess you could use it to turn on prox switches or items using low current, would this actually save $$$ on power bill? This way, you are only turning on these devices when you actually need them to work.
Why you ask this interesting question at end of day sir, now I will be thinking of nothing else but this question.
Why you ask this interesting question at end of day sir, now I will be thinking of nothing else but this question.
ronaldshelton28
Member
OP
Sorry i was not complete with description. I have a system that gets input from a remote card to lock out the pendant so that stuff cannot be changed if the input is on system is locked. I thought about using a button on a HMI to turn this off or on hence using the output to turn on the input.
Ken Moore
Lifetime Supporting Member
On Safety Systems, we used to use Standard outputs to fire double pole relay. We used one pole for the field device and one pole for feedback into the PLC. So we would know if a relay failed to turn off, we would then kill power to the output card, killing all the outputs and tripping the system.
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