I am working on a project to use existing gate sensors to trigger an alert.
I have 4 gates in a parking lot that include beam sensors to prevent gate from closing on a car.
I have unused wires running from each gate operator to the building.
I want to hook up 2 wires from each sensor and have them trigger something in the building when the sensor closes its relay.

The problem is, I need for each pair coming from the sensors to be isolated from each other, so when gate 1 is triggered, it does not short out gate 2, 3 and 4 affecting their gate operator.

Can someone tell me how I can tie all 4 sensors into 1 unit that will detect an input on any of the 4 triggering an output and at the same time not interfere with each other? All inputs from the gates are simple relays with no voltage present.

My initial thoughts were something like an alarm panel with multiple zone contacts but I am looking for something more simple and inexpensive to build.

Thanks

Larry

 

How about this?

 

Simple with steering diodes one in each conductor.
Max.

 

How about this?
View attachment 118097

Thank you Alec_t

Maybe I am not viewing the schematic properly, but I have 4 pairs of wires coming from different areas. There is no common ground.
Just the same way door contact switches or motion sensors would wire into an alarm panel, I need to take the 4 pairs of wires and make it if any one or more pairs short, it will close a relay for the output. And at the same time, when one of the pairs short, it will not produce a short back to any of the other pairs.

Thanks again for the reply.

 

If the devices are simple contact closure then at the terminating end common up one from each and then place a diode rectifier in each of the other leads, each would then be capable of sinking one side of a relay (or) coil in the termination end.
What is the 'trigger something in the building'?
Max.

 

I have 4 pairs of wires coming from different areas. There is no common ground.

You can ground one wire of each pair to make a common fround. However, I prefer Max's solution which is simpler to implement.