sdinsmor

Choosing PLC - Not Sure if I need Open Drain or Collector

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I am interfacing a CNC machine to an external industrial controller, and need to choose a PLC to do so. I used to be a computer engineer once upon a time, but I’m a little rusty :) Communication from CNC to PLC will be wireless TCP, and the interface from the PLC to the industrial controller will be just one 0-10V analog output and two digital I/O. I don’t want to be adding resistors or anything, just straight connections between the PLC & controller. Below is the block diagram for the industrial controller, not sure if I need open collector or open drain, or if I can use either depending on how I source COM_1. I’ve attached the block diagram as well as the data sheet for the controller for reference (I’ll be working off the DB-25). Thank you in advance!!

 

DFA285E5-80A1-43BF-8CCA-73C0E00F7169.jpeg

Gray-Tech_01_E3000.pdf

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this supports connections of either polarity so - PLC digital I/O could be any 24V type, either PNP/NPN. PLC analog output will need to be 0-10V of course. it will connect to VR and GND, +10V terminal will not be connected. 

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Hi Panic,

Thanks for the quick reply, somehow the response email got routed to my spam, so I just saw it. Thank you very much! Does it matter if I connect COM_1 to 0V or 24V?

Edited by sdinsmor

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it may....you cannot  just arbitrarily connect things to each other.

this device does not care about polarity but it still matters what is on the other side and for it to work you need to complete the circuit so there is a current path.

 

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Analog output doesn't have much issue, just connect GND and your PLC Analog OUT to VR in your Industrial Controller.

For your digital outputs I would recommend using relays to avoid connecting the two devices directly. Specially if you are not sure about the functioning of your PLC I/O. As others have stated, your machine can work either way, but it doesn't mean that you shouldn't be careful with the way you connect things to each other. In general, I think NPN logic is better for this case.

By the way, Open Drain and Open Collector are almost the same thing, the difference being that one is used in the case of MOSFET and the other one in the case of BJT. Maybe you are thinking about Sinking vs Sourcing I/O?

Best regards!

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