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GBerkheimer

Is my PLC or UID 0808R broken? (not reading physical IOs)

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I have a 7" UniStream plc that is controlling and communicating between power supplies, electrical testers, shunts, and multiple IAI linear actuator controllers (all via ethernet IP and Serial COM) which took me two months to program and get working correctly. The last step was to swap out a touchscreen button bit, which simulated the binary state of a safety interlock,  with a link to the safety switch on the equipment.  Simply, its an external push button that passes through -24V DC.   None of the IO bits are changing state in the UniApps IO tags screen when this "push button" is pressed. We have verified  (with a digital multi-meter) that the signal and push button are functioning correctly. We have also tested multiple input ports just to make sure we didnt have a bad port situation. I am anxious to get this project wrapped up. I cant believe one simple physical input is defeating us here. See attached image for our hookup to the UID 0808R (Sink method).

 

safety interlock - 0808r wiring-min.pdf

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Hi GB, I am exceptionally bothered by your description of "0V from other equipment".  If you don't have your 0s commoned, this could be the issue.  Try it with just the PLCs supply as the power source for the physical switch, and only that supply's 0v in use everywhere......

And For Everyone's Information,  I always ensure that all control gear is on the same phase.   It makes it so much easier to avoid complex issues that can arise, including higher voltages than expected.

cheers,

Aus

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And another few things:

I'm assuming that the "24V power supply" actually has it's 0V connected to 2....your diagram implies it isn't.

Checked your blue 0V connection line for continuity?

Have you tried simply bridging with small test leads direct from your plc power to the inputs?

And lastly I just noticed this, but very important!:

On 7/7/2018 at 12:31 AM, GBerkheimer said:

passes through -24V DC. 

"-24DC" ???  Is the "-" a typo or are you really referring to 0V, as in 24v dc + = 24V, and 24v dc - = 0V?  If you are using the - terminal for your switch source, that is your problem.....you need to be supplying 24+ into I0 via the switch.

cheers,

Aus

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