I/O Module Troubleshooting; Input Circuit Troubleshooting - Mitsubishi MELSEC- Q Q12PHCPU User Manual

11 TROUBLESHOOTING

11.5 I/O Module Troubleshooting

11.5.1 Input circuit troubleshooting

Condition
• Leakage current of input switch
(e.g. drive by non-contact switch).
Input signal
does not
turn OFF.
• Drive by a limit switch with neon lamp.
Input signal
does not
turn OFF.
• Leakage current due to line capacity of wiring
cable.
(Line capacity C of twisted pair wire is approx.
100 PF/m).
Input signal
does not
turn OFF.
• Drive by switch with LED indicator.
Input signal
does not
turn OFF.
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This chapter explains possible problems with I/O circuits and their corrective actions.
This section describes possible problems with input circuits and their corrective
actions.
Input Circuit Problems and Corrective Actions
Cause
Leakage
current
Power supply
Leakage
current
Power supply
Leakage
current
Power supply
Leakage
current
• Connect an appropriate resistor which will
make the voltage across the terminals of the
input module lower than the OFF voltage
AC input
value.
Input module
It is recommended to use 0.1 to 47 F + 47 to
120 (1/2W) for the CR constant.
• Same as Example 1.
• Or make up another independent display
AC input
circuit.
Input module
• Same as Example 1.
• However, leakage current is not generated
when the power supply is located in the input
equipment side as shown below.
AC input
Input module
• Connect a register which will make the voltage
between the input module terminal and
DC input
(plus common)
common lower than the OFF voltage, as
shown below.
Input module
A calculation example of a value for a
connected resistor is given on the following
page.
MELSEC-Q
Corrective Action
AC input
Input module
AC input
Input module
Power supply
DC input
(plus common)
Resistor
Input module
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