11 - 8 11 - 8
MELSEC-Q
11 I/O MODULE TROUBLESHOOTING
Table 11.2 Output Circuit Problems and Corrective Actions (Continued)
Condition Cause Corrective action
Example 6
The load
operates only by
powering on the
external power
supply.
(transistor
output)
The polarity to connect the external power supply is reverse.
If the external power supply is connected with wrong polarity,
current may flow across an output element protection diode to
the load.
Connect the external power supply with
correct polarity.
Example 7
When an output
is turned on, a
load connected
to the other
output is also
turned on.
(transistor
output (source
type))
If the wire connecting 0V of an external power supply and a
common of a load is cut off or disconnected, a current flows to
the load that is off due to a parasitic circuit of the output
element that is off.
If a current keeps flowing under the above condition, a failure
may occur.
Connect the external power supply and
loads correctly.
To prevent the condition described on the
left, connect a diode to each output terminal
as shown below.
Load
External
power
supply
Y0
COM
Incorrect Correct
Transistor
output module
Output element
protection diode
To Next Page
Loading...
Need help?
General
