input on inputs?

bce123

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I have a micro logix 1763 L16bwa I am thinking about using both pnp and npn input devices on the base inputs. I have look at the 1763 um001 manual (page 50 and 51)and I can not find a NO do not do this. your inputs would be most welcomed on this subject. Thanks
 
I see nothing formally wrong with this, and would do it with no hesitations, should it become necessary. On the other hand, proper documentation, and probably a warning sticker in the proximity, would be required to avoid misunderstandings.
 
Should not be a problem if you put the "PNP" and the "NPN" in different groups.
thats the way I read it Just never done it that way I have always used a sepearte card. however this is a small project and I would like to keep the cost down. was just not sure when i saw the wiring diag. showing either way but not both on the same diag.
 
Considering the polarity of the DC COM terminal would be opposite for NPN and PNP sensors per group.
If there is no isolation ( i.e. internal continuity) between DC COM terminals of each group, both NPN and PNP
connections would not be possible.

pnpnpn.jpg
 
Considering the polarity of the DC COM terminal would be opposite for NPN and PNP sensors per group.
If there is no isolation ( i.e. internal continuity) between DC COM terminals of each group, both NPN and PNP
connections would not be possible.
I did not know this! Now I see that the 'COM' terminals on the 1100 are not labeled 'COM 1', 'COM 2', etc. like a 1400, so I guess this is true. Why bother having multiple COM terminals then? Odd that they group them as DCa and DCb... :unsure:

Another interesting note from the ML1400 User Manual...

"For 1766-L32BXB and 1766-L32BXBA controllers, the VDC NEUT or common terminal of the power supply is also connected to chassis ground internally."

The ML1100 manual says the same thing is true for the DC powered 1100s.

Therefore, if you choose to use a floating DC power supply, the ML1400 circumvents that... :rolleyes:

I never use the built-in DC supply on the AC powered models, but for those that do:

"For 1766-L32BWA and 1766-L32BWAA controllers, the COM of the sensor supply is also connected to chassis ground internally."

🍻

-Eric
 
There is nothing wrong with the PLC referencing its power supply to ground. This doesn't prevent you from using a floating 24vdc supply for the sensors.

I would lean toward converting them to a common PLC wiring scheme with interface terminals (or interfacing field plugs for standard DC connectors) to keep it simple at the PLC level.
 
There is nothing wrong with the PLC referencing its power supply to ground. This doesn't prevent you from using a floating 24vdc supply for the sensors.
I agree. There is nothing wrong with the PLC referencing its (built-in 24VDC) power supply to ground. I am talking about the PLC referencing MY power supply to ground. I am referring to this part:

"For 1766-L32BXB and 1766-L32BXBA controllers, the VDC NEUT or common terminal of the power supply is also connected to chassis ground internally."

That's the terminal for the INCOMING power, supplied TO the PLC (on 24VDC models), not the built-in supply for sensors.

I just find it odd that they would intentionally ground that terminal... :confused:

Not that big of a deal, but just wanted to point out the fact that this terminal is grounded. I discovered this in the manual after wondering why my floating supply was no longer floating.

🍻

-Eric
 
Output on the inputs is yes they are working. this of course is done using two separate input groups. so it seems the two com. terms are truly isolated
 
I agree. There is nothing wrong with the PLC referencing its (built-in 24VDC) power supply to ground. I am talking about the PLC referencing MY power supply to ground. I am referring to this part:

"For 1766-L32BXB and 1766-L32BXBA controllers, the VDC NEUT or common terminal of the power supply is also connected to chassis ground internally."

That's the terminal for the INCOMING power, supplied TO the PLC (on 24VDC models), not the built-in supply for sensors.

I just find it odd that they would intentionally ground that terminal... :confused:

Not that big of a deal, but just wanted to point out the fact that this terminal is grounded. I discovered this in the manual after wondering why my floating supply was no longer floating.

🍻

-Eric

Oh, that is bad, I read it as meaning the terminals of the DC output of the PLC power supply.

Yes, no need to loop your grounds for you against your will, huh?
 

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