Bad idea?

[Bob O]

I am going to be watching to see if any one or more of six PE’s goes high but at this time I don’t need to know which one. I don’t have enough spare inputs so how bad is it to tie all six of the PE’s outputs into one? All six PE’s are the same. Thanks, Bob

[Steve Bailey]

All photoeyes, being solid-state devices have some leakage current in the off state. Wiring six of them in parallel will apply the sum of the leakage currents of all six to the PLC input. If this results in an input that is always on, you will need to add an interposing relay.

[TimWilborne]

My only objection would be trying to figure out which one is on when it is not suppose to be. Make sure there are LED indicators on the photoeyes

[panic mode]

If they are DC sensors, I wouldn't worry too much about leakage. this is serious issue on AC but leakage current DC sensors I tested is hardly measurable and impedance of PLC inputs is quite low (2-4kOhm). we have been paralleling few sensors here and there without issues. if the sensor output is "open collector" or equivalent, this is just fine. i haven't run accros them yet (and don't know if they exist) but if your sensors would have complementary or totempole output (push-pull) then you need to protect them (use diodes as an OR gate) or they will short each other out as soon as they don't see same thing. this type of output is quite common in certain circuits but as said, I have not seen that in industrial sensor. that would be nice for photoeyes with light-on/dark-on switch, or sensors with complementary outputs (NO and NC) because such device would work with all plcs regardless if PNP or NPN, one could stock just one part number.

[Bob O]

Thanks guys.