Parallel interconnection of outputs with S7-21x and S7-22x
Can I interconnect the DC outputs for the S7-21x and S7-22x CPUs in parallel.
CPU outputs are normal PNP transistors and should not be interconnected in parallel because of the asymmetry in the load and the different switch-on delays.
You can solve the problem by using a CPU 215, 216, 221, 222,
224, 226, 226XM or an EM223 expansion module.
All outputs of these units have FET transistors which can support a wired OR connection.