Mitsubishi Electric · MELSEC iQ-R I/O Module
An input signal does not turn off due to a sneak path current created by the use of two power supplies in the system. This unintended current flow bypasses the intended circuit, keeping the input module falsely activated, especially when voltage E1 is greater than E2.
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Consolidate the input circuit to use a single power supply to eliminate the conditions for a sneak path.
If two power supplies are absolutely necessary, connect a diode in series with the input device to block any reverse current flow and prevent the sneak path.