protecting output PLC

[smsebnaa]

Thanks ivo.maenen.

Maybe some sort of debounce logic would help.If I understand your problem correctly. See curlyandshemp's post at link below.


https://www.google.com/url?sa=t&rct...6oQeNBybaWNEPrNXw&sig2=vA0PUkWhTqtQSZssgA-R1g

i think, i should use selector switch with 3 state to disconnect main contactor in transition from auto to manual. i used 2 state.

 

[Mickey]

i think, i should use selector switch with 3 state to disconnect main contactor in transition from auto to manual. i used 2 state.

That would not change the above suggestion to use some sort of debounce
logic. Again, if I understand your problem.

 

[smsebnaa]

can you speak about bounce? what is bounce or debounce?

 

[Mickey]

See links...

In your case its used to create a "make before break" switch.

https://www.google.com/?gws_rd=ssl#q=debounce+explained

 

[Bit_Bucket_07]

i think, i should use selector switch with 3 state to disconnect main contactor in transition from auto to manual. i used 2 state.

I wouldn't recommend a software patch for a hardware design flaw. Simply wire your HOA selector switch so that the PLC output is isolated from the load when you switch to manual mode.

 

[kallileo]

Something like the this:

 

[Bit_Bucket_07]

Something like the this:

Yep. Simple solution for a simple problem.

 

[smsebnaa]

Something like the this:

your solution is good but where is the plc's input?

 

[Mark Snodgrass]

Why not have the selector switch send both AUTO and MANUAL signals to the PLC as two inputs, and use the PLC output as the power for the contactor in both AUTO and MANUAL modes. Use the PLC logic decide how the output comes on if AUTO input is on or if MANUAL input is on.

 

[kallileo]

There are more that one way to achieve the result you need.
What Mark says is also correct.

You can install an additional contact and use it to signal a DI but then you will have to do software modifications as well.

 

[JRB]

This way the PLC knows what mode the motor is in.

 

[smsebnaa]

thanks everybody, specially Mark and JRB for very very good solution. you changed my bad decision.

 

[Bit_Bucket_07]

Why not have the selector switch send both AUTO and MANUAL signals to the PLC as two inputs, and use the PLC output as the power for the contactor in both AUTO and MANUAL modes. Use the PLC logic decide how the output comes on if AUTO input is on or if MANUAL input is on.

One typically desires for the motor to be operational when the PLC is not available, if an HOA selector switch is installed.

 

[JRB]

You're right Bit Bucket, and so is everyone else. It all depends on exactly what smsebnaa wants to do.

I hope smsebnaa keeps that in mind.