Chapter 12. TROUBLE SHOOTING
12 - 9
12.4.2 Output circuit troubles and corrective actions
The following desires possible troubles with output circuits, as well as corrective actions
Condition
Cause
Corrective Action
When the output is Off,
excessive voltage is
applied to the load
•
Load is half-wave rectified inside
(in some cases, it is true of a solenoid)
•
When the polarity of the power supply
is as shown in
ℵ
, C is charged. When
the polarity is as shown in
ℑ
, the voltage
charged in C plus the line voltage are
applied across D. Max voltage is approx.
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
•
Connect registers of tens to hundreds
k
Ω
across the load in parallel
The load does not turn
OFF
•
Leakage current by surge absorbing
circuit which is connected to output
element in parallel
•
Connect C and R across the load,
which are of registers 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
•
Leakage current by surge absorbing
circuit which is connected to output
element in parallel
•
Drive the relay using a contact and
drive the C-R type timer using the since
contact
•
Use other timer than the C-R contact
Some timers have half-ware rectified internal
circuits therefore, be cautious
.
The load does not turn
OFF
•
Sneak current due to the use of two
different power supplies
•
E1
<
E2 : sneak current
•
E1 is switched Off and E2 is switched
ON : sneak current
•
Use only one power supply
•
Connect a sneak current prevention
diode(Figure below)
If the load is the relay, etc, connect a
counter-electromotive voltage absorbing
code as show by the dot line
