Mitsubishi QX10 User Manual page 135

11 I/O MODULE TROUBLESHOOTING
Table 11.1 Input Circuit Problems and Corrective Actions (Continued)
Condition
An input • Drive by switch with LED indicator.
signal does
not turn off.
An input • Current flow in the opposite direction due to
signal does the use of two power supplies
not turn off.
An input Stepwise distortion as shown below appears to
signal does the zero cross voltage of input signal (AC).
not turn on
(AC input
Zero cross
module).
voltage
False input Noise has been taken as input data.
due to
noise
*1: If excessive noise is periodically generated, setting a shorter response time value may be effective.
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Cause
DC input
Lamp
Input
E2
module
E1>E2
Corrective action
Connect an appropriate resistor so that the
current flow within the module will be less than
the off current.
A calculation example of a value for a
connected resistor is given on the following
page.
• Use only one power supply.
• Connect a diode so that current flows only in
one direction. (Figure below)
DC input
E1
Input
Lamp
module
Improve input signal waveform by using the
uninterruptible power system etc.
Change the response time setting value.
Example
1ms 5ms
If this action is not effective, take the following
measures.
• To prevent excessive noise, avoid installing
power cables together with I/O cables.
• Take noise reduction measures. (Example:
Connect surge absorbers to noise-generating
devices such as relays and contactors using
the same power supply.)
MELSEC-Q
Diode
E2 E1
*1
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