I/O Module Troubleshooting - Mitsubishi Electric Q172DCPU User Manual

6 INSPECTION AND MAINTENANCE

6.6.4 I/O module troubleshooting

Condition
• Leakage current of input switch
(e.g. drive by non-contact switch).
Input signal
is not
turned
OFF.
• Drive by a limit switch with neon lamp.
Input signal
is not
turned
OFF.
• Leakage current due to line capacity of wiring
cable.
(Line capacity C of twisted pair wire is approx.
100 pF/m).
Input signal
is not
turned
OFF.
• Drive by switch with LED indicator.
Input signal
is not
turned
OFF.
This section describes possible problems with I/O circuits and their corrective actions.
(1) Input circuit troubleshooting
The following describes possible problems with input circuits and their corrective
actions.
Input Circuit Troubleshooting and Corrective Action
Cause
Leakage
current
Power supply
Leakage
current
Power supply
Leakage
C
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 0.47 [ µ F] + 47
to 120 [ ] (1/2W) for the CR constant.
• Same as Example 1.
• Provide an independent display circuit
AC input
separately.
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
common lower than the OFF voltage value, as
shown below.
DC input
(plus common)
Input module
(Note-1) : A calculation example of a value for a
6 - 26
Corrective action
AC input
Input module
AC input
Input module
C
Power supply
DC input
(plus common)
R
Resistor
Input module
connected resistor is given on the
following page.