I/O Connection Troubleshooting; Input Circuit Troubleshooting - Mitsubishi A1SJH User Manual

11. TROUBLESHOOTING
11.4

I/O Connection Troubleshooting

11.4.1

Input circuit troubleshooting

Condition
Input signal
Example
does not turn
1
OFF
Input signal
Example
does not turn
2
OFF
Input signal
Example
does not turn
3
OFF
Input signal
Example
does not turn
4
OFF
This section explains possible problems with I/O circuits.
This section describes possible problems with input circuits, and corrective action.
Table 11.2 Input circuit problems and corrective action
Cause
Leakage current of input switch (e.g. drive by non-
contact switch).
C
Leakage current
R
Power supply
Drive by a limit switch with neon lamp.
Leakage
current
Power supply
Leakage current due to line capacity of wiring cable.
(Line capacity C of twisted pair wire is approx. 100
PF/m).
Leakage
current
Power supply
Drive by switch with LED indicator.
Leakage
current
• Connect an appropriate resistor which will
make the voltage across the terminals of the
input module lower than the OFF voltage value.
AC input
Input module
It is recommended to use 0.1 to 0.47 µF + 47 to
120 Ω (1/2 W) 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
common higher than the OFF voltage, as
shown below.
DC input (sink)
Input module
* An example calculation of a value for a
connected resistor is given on the following
page.
11 - 16
MELSEC-A
Corrective action
AC input
C
Input
module
R
AC input
Input
module
Power supply
DC input (sink)
Resistor
Input
module