Chapter 10 Troubleshooting
10-9
10.4.2 Output circuit troubles and corrective actions
The following describes possible troubles with input circuits, as well as their corrective actions
.
Condition
Cause
Corrective Action
When the output
is off, excessive
voltage is
applied to the
load.
y
Load is half-wave rectified inside (in some
cases, it is true of a solenoid)
y
When the polarity of the power supply is as
shown in , C is charged. When the polarity is
①
as shown in , the voltage charged in C plus
②
the line voltage are applied across D. Max.
voltage is approx. 2
√
2.
*) If a resistor is used in this way, it does not
pose a problem to the output element. But it may
make the performance of the diode (D), which is
built in the load, drop to cause problems.
y
Connect resistors of tens to hundreds K
Ω
across the load in parallel.
The load
doesn’t turn off.
y
Current leakage by surge absorbing circuit,
which is connected to output element in parallel.
y
Connect C and R across the load, which are of
resistors of tens K
Ω
. When the wiring distance
from the output module to the load is long, there
may be a leakage current due to the line
capacity.
When the load
is C-R type
timer, time
constant
fluctuates.
y
Current leakage by surge absorbing circuit,
which is connected to output element in parallel.
y
Drive the relay using a contact and drive the C-
R type timer using the since contact.
y
Use other timer than the C
−
R contact some
timers have half-ware rectified internal circuits
therefore, be cautious.
R
Load
R
Load
C
C
R
Load
Leakage current
Output
~
C
R
Load
Leakage current
Output
~
X
T
Timer
Output
~
C
R
Load
D
~
C
R
Load
R
D
~
