Hello,

Noob question, how do I connect an output from the Allen Bradley RS LOGIC 500 PLC to an input from siemens PLC 300,
1 wire from the AB output to the Siemens input?
I need the output in my Siemens PLC (to make an alarm)

Thank you,

I am going to assume that both the A-B output and the Siemens input are both 24VDC. If so, and, this is very important:
IF the A-B output card AND the Siemens input card receive power from the SAME power supply, you can connect the output wire from the sourcing output of the A-B PLC to the sinking input of the Siemens PLC. Since each I/O card is connected to the same power supply, the commons are connected locally at each card.

If the two I/O cards are NOT on the same 24VDC power supply, then you will need to use an interposing relay. The A-B output will be connected to the coil of the relay, and a NO contact on the relay will be connected to the Siemens digital input.

Thank you, i need an interposing relay