Instruction manual

6 - 27
6 INSPECTION AND MAINTENANCE
6.6.4 Internal input circuit troubleshooting
QDS
This section describes possible problems with internal input circuits and their corrective
actions.
(1) Internal input circuit troubleshooting
The following describes possible problems with internal input circuits and their
corrective actions.
Table 6.4 Internal Input Circuit Troubleshooting and Corrective Action
Condition Cause Corrective action
Example 1
Internal input
signal is not
turned OFF.
• Drive by switch with LED indicator.
Motion CPU
Leakage
current
DC input
(plus common)
• Connect an appropriate resistor so that the
current across the Motion CPU becomes lower
than the off current.
DC input
(plus common)
Motion CPU
Resistor
(Note): A calculation example of the resistance to
be connected is shown below.
Example 2
Internal input
signal is not
turned OFF.
• Sneak path due to the use of two power
supplies.
E1
Motion CPU
E2
DC input
E1>E2
• Use only one power supply.
• Connect a sneak path prevention diode.
(Figure below)
Motion CPU
DC input
E1 E2
<Calculation example of Example 1>
If a switch with LED display is connected to Motion CPU, and current of 4 [mA] is
leaked.
Leakage
current 4[mA]
Motion CPU
Input signal
part
24VDC
3.6k[ ]
(a) Because the condition for OFF voltage (0.9[mA]) of Motion CPU is not
satisfied. Connect a resistor as shown below.
24VDC
Input impedance
5.6k[ ]
Iz=0.9[mA]
Motion CPU
Iz=3.1[mA]
4[mA]
3.6k[ ]