Mitsubishi Electric MELSEC-L Series User Manual page 76

(e) Case 5
By using two power supplies, a sneak path has been configured.
Cause
• Use one power supply.
• To prevent the sneak path, connect a diode as shown below.
Action
(2) An input signal does not turn on. (AC input module)
Stepwise distortions as shown below appear to the zero cross voltage of an input signal (AC).
Cause
Action Improve the input signal waveform by using online UPS.
(3) A signal incorrectly inputs data.
Cause Noise has been taken as input data.
Set the input response time longer. (Page 69, Section 7.1)
(Example) 1ms  5ms
If this action is not effective, also take the following two measures.
Action
• To prevent excessive noise, avoid installing power cables together with I/O cables.
• Connect surge absorbers to noise-generating devices such as relays and conductors using the same power supply or take other noise
reduction measures.
If excessive noise is periodically generated, setting the response time shorter may be effective.
(Example) 70ms  20ms
74
Case
Lamp
Input
module
DC input
Input
Lamp
E2
module
Case
Zero cross
voltage
Case
E2 E1
E1>E2
Diode
E1